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Title Alveolar distraction osteogenesis for dental implant

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									             Alveolar distraction osteogenesis for dental implant
   Title     rehabilitation in reconstructed jaws


Author(s)    Hariri, Firdaus



 Citation



Issue Date   2010



  URL        http://hdl.handle.net/10722/130874



  Rights     unrestricted
Alveolar Distraction Osteogenesis for Dental
Implant Rehabilitation in Reconstructed Jaws
 A dissertation submitted for the degree of Master of Dental Surgery

                                By:

                   Dr. Firdaus Hariri, BDS




                    Oral & Maxillofacial Surgery
                        Faculty of Dentistry
                    The University of Hong Kong



                            August 2010



                            Supervisor:

                        Prof. Lim K. Cheung
         BDS, FFDRCS, FRACDS(OMS), FCDSHK(OMS), PhD



                          Co-Supervisor:

                         Dr. Hannah Chua
                   DMD, MA, MDS, MOSRCS, PhD
                                   Declaration



I declare that this thesis represents my own work, except where due
acknowledgement is made, and that it has not been previously included in a
thesis, dissertation or report submitted to this University or to any other institution
for a degree, diploma or other qualification.




                                   Firdaus Hariri




                                          1
                             Acknowledgement


It is certainly not easy trying to record, in this single page, my gratitude to the
people who have made such a tremendous impact on my life. Thank you for
being a teacher, a family and a friend.




First and foremost, thank you to my supervisor, Prof. Lim K. Cheung for the
continuous support and guidance throughout my three years of study. For being
a teacher who believes in me, who tugs and pushes and leads me to the next
level, and sometimes poking me with a sharp stick called "truth." Reality bites, or
so they say.




To my co-supervisor, Dr. Hannah Chua, thank you for your encouragement, for
sharing your knowledge and for being a passionate teacher who teaches from
the heart.




Thank you to Prof. Samman for being the teacher who greatly inspires. Your
principles and values affect eternity; never can you conceive how great your
influence has been on me.




Thank you to all the academic staffs for sharing your knowledge and for
extending a helping hand and to the greatest backbones any department could
have; the nurses, DSAs and administrative staffs of the Department of Oral and
Maxillofacial Surgery.




                                          2
You meet people who forget you. You forget people you meet. But sometimes
you meet those people you can't forget. To my batch mates, Fahmi, Syed, Rama,
Dharma, Jessie, Ivan and Valentina, thank you for the laughter and tears and for
supporting each other through both good and bad times.

Other things may change us, but we start and end with family. To my beloved
family; my wife, my children and my parents; thank you for your prayers, support
and understanding. The happiest moments of my life have been the few which I
have spent at home with you.

“What, what can I give you in return…"




                                         3
Abstract

Objectives

1. To conduct a comprehensive review of the alveolar distractors available and

highlight their characteristics.

2. To conduct a systematic review on the published literature involving alveolar

distraction osteogenesis (ADO) for reconstructed jaws, with particular emphasis

on clinical indications, critical surgical factors, protocol and complications in oral

rehabilitation for reconstructed jaws.

3. To present the clinical experience on ADO in fibula reconstructed mandibles

and evaluate the outcomes in treatment of severe vertical discrepancy between

transplanted fibula and the residual alveolar bone prior to dental implant

placement.



Material and methods

The methods and results are organized to correspond to the 3 objectives as

follows:

1. Alveolar distraction osteogenesis: a compendium of devices

Literature and product catalogue search was performed to review and summarize

all the available ADO systems. Specific indications and principles of ADO were

listed in Excel file. The systems were categorized into vertical distraction (intra-

osseous, extra-osseous and tooth-borne device), transverse distraction,

bidirectional alveolar distraction and implant distractor (dental implant distraction




                                          4
device, implant distractor for reconstructive surgery). An overview and the

mechanism of each distraction system were elaborated.



2. Alveolar distraction osteogenesis for oral rehabilitation in reconstructed jaws:

a systematic review

Online literature search of PUBMED was performed using selected keywords

from January 1996 to December 2009 according to the guideline of PRISMA

statement. The searches confined to publications in English language according

to pre-determined inclusion and exclusion criteria. A total of 18 papers were

identified and included in this review. Data extraction and summarization were

conducted to analyze the specific parameters.



3. Alveolar distraction osteogenesis for dental implants rehabilitation in

reconstructed mandible

Five patients (2 males and 3 females) ranging from 25 to 60 years old (mean age

= 42.2 years old) under the care of the Discipline of Oral and Maxillofacial

Surgery, The University of Hong Kong, underwent fibula distraction procedure

after having mandibular reconstruction with vascularized free fibula bone graft.

The indication for application of ADO was to correct the vertical discrepancy

between the reconstructed region and residual alveolar ridge in order to achieve

adequate vertical bone height prior to implant placement.




                                        5
Results

1. Alveolar distraction osteogenesis: a compendium of devices

The current available systems not only allow distraction in linear and bidirectional

direction, but also angulation adjustment to achieve vector control. The

development of integrated distraction dental implant devices can reduce the

overall treatment duration and overcome some limitations of conventional

alveolar distractors.



2. Alveolar distraction osteogenesis for oral rehabilitation in reconstructed jaws:

a systematic review

A total of 43 cases of ADO in reconstructed jaws were reported in 18 articles.

There are only 5 studies that reported more than 3 cases. The jaw defects were

mostly resulted from malignancy, benign tumour or gunshot injury. The defects

were reconstructed with mostly by vascularized fibula graft (33 cases). ADO was

primarily indicated to correct vertical discrepancy between the reconstructed

region and residual ridge in order to achieve adequate height of the transplanted

bone prior to implant placement. All distractors used for this method were

intraoral devices, with mostly extraosseous distractors. The vertical bone height

gained ranged from 6 mm to 15 mm. 15 studies mentioned further rehabilitation

with dental implants with follow up period ranged from 2 to 81 months. The most

common complications reported were infections and haematoma.




                                         6
3. Alveolar distraction osteogenesis for dental implants rehabilitation in

reconstructed mandible

Four patients had segmental mandibulectomy due to ameloblastoma and 1 due

to osteoradionecrosis. All 5 cases involved reconstructive procedure with left

fibula vascularized bone flap. The timing of placement of distractor after fibula

reconstruction ranged from 8 to 65 months (mean = 24.4 months). Latency

period ranged from 3 to 7 days (mean = 5.6 days). Distraction rate applied

ranged from 0.35 mm to 0.7 mm daily. The vertical bone height achieved ranged

from 11.2 mm to 17.5 mm (mean = 13.58 mm). Consolidation period ranged from

6 to 27 weeks (mean = 15 weeks). A total of 22 dental implants were placed in all

the 5 cases. Follow-up period starting from the completion of alveolar distraction

procedure ranged from 8 to 32 months (mean = 19.6 months). Implant follow-up

ranged from 1 to 33 months (mean = 14 months). Bone biopsies showed the

distracted area was filled with newly formed bony trabeculae and viable bone. The most

common complication occurred was chronic mucosal infection around the

distractor rod.



Conclusions

1. Alveolar distractors have improved in design through the years with many

choices available in the market. Some designs have integrated distraction

mechanism with dental implants to reduce time to reach the rehabilitation goal.

2. This systematic review on ADO reveals few numbers of case series in this

topic and lack of randomized controlled trials. ADO in reconstructed jaws can




                                          7
produce consistent evidence of bone regeneration with stable augmentation

results clinically, histologically and radiographically, thus making it a predictable

surgical procedure prior to dental implantations.

3. ADO in reconstructed mandibles produced consistent evidence of bone

regeneration with stable augmentation. It is a predictable surgical procedure to

treat severe vertical discrepancy between the transplanted fibula and the residual

alveolar bone prior to implant placement in reconstructed mandibles. The

procedure comes with a minor risk of chronic infection around the distractors.




                                         8
                                          Contents


Declaration                                          1
Acknowledgements                                     2
Abstract                                             4
Table of Contents                                    9
Part I:                                              10
           Introduction                              11
           ADO in oral and maxillofacial surgery     14
           Indications                               16
           The principle of ADO                      17
           Alveolar distraction devices              20
           Conclusion                                45
           References                                47
Part II:                                             53
           Introduction                              54
           Material and Methods                      58
           Results                                   59
           Discussion                                62
           Conclusion                                76
           References                                77
Part III:                                            91
           Introduction                              92
           Material and Methods                      95
           Results                                   103
           Discussion                                113
           Conclusion                                123
           References                                124




                                             9
                             Part I:

  Alveolar distraction osteogenesis:
      a compendium of devices

Submitted to: International Journal of Oral and Maxillofacial Implants




                                  10
1.0    Introduction


Distraction osteogenesis is a clinical tissue engineering technique that involves

regeneration of new bone from a gradual incremental traction between bony

segments. The process begins when a distraction force is applied to the healing

callus that joins the divided bone ends and will also simultaneously create

tension to the surrounding soft tissue thus initiating a sequence of soft tissue

expansion as well.1


The introduction of distraction osteogenesis (DO) has embarked a new revolution

in biomedical engineering. Even though mechanical manipulation of bone

segments has been described by Hippocrates for more than 2,000 years ago, it

was not until Guy de Chauliac, a French surgeon described the application of

pulley system for continuous traction to treat femoral fractures in the fourteenth

century.1 In 1905, Alessandro Codivilla, an Italian surgeon used a transcalcaneal

metal pin as a method of applying skeletal traction to correct malunited fractures

and deformities.2,   3
                         Vittorio Putti in 1921 then developed a unilateral fixator,

known as “Osteoton” which could monitor the traction force during femoral

lengthening.4 In 1927, Abbot described the use of bilateral external skeletal

fixator for tibial lengthening.5,   6
                                        Further development in distraction osteogenesis

technique in the 1930s were also reported by studies conducted by Haboush and

Bosworth.1 But a series of reported complications, which included delayed

healing, non-union, deformities, fractures and soft tissue problems, have




                                               11
hampered this technique so much that it became obsolete from the orthopedic

surgeons’ armamentarium.1


The rigid metallic rings and attachments system designed by Gavriil Ilizarov in

1951 has contributed to significant revolution to distraction osteogenesis. The

new device consisted of two metal rings joined together with threaded rods. The

bone segments were held to the rings with two transosseous wires that were

inserted at a right angle to each other. Ilivarov also discovered and established

two basic principles of distraction osteogenesis, which came to be known as

“Ilizarov Effects”: (1) the law of tension-stress and its effects on the genesis and

growth of tissues; and (2) the influence of blood supply and mechanical load on

the shape of bones and joints.7-11


Ilizarov’s new discovery in distraction osteogenesis however remained

unrecognized in most part of the world due to his language limitation to Russian

only. Wagner’s technique of treating leg length discrepancy remained a standard

technique in the 1970s. The technique involved three separate operations which

consist of open osteotomy, application of external fixator with 5 mm lengthening

and placement of cancellous bone graft in the gap followed by internal plating to

replace the external fixator.1


Snyder in 1973 was the first to experiment distraction osteogenesis in

craniofacial field by having the first animal study to lengthen a canine mandible

using a Swanson external fixator.12 The success of Snyder’s work has prompted

Michieli and Miotti to modify his work by using an intraoral cap splint device in



                                        12
1976.13 Kutsevliak and Sukachev in 1984 then conducted a study that

successfully lengthen a normal canine mandible up to 1.2 cm based on Ilizarov’s

principle and studied the histological healing of the distraction regenerate.14 Karp

et al. conducted a similar histological study to demonstrate the healing process of

mandibular intramembranous bone mineralization during distraction and showed

that the dynamics of the new bone formation is similar to that of long bones as

described by Ilizarov.15, 16


The contribution by Ilizarov was internationally recognized only in the late 1980s

after he successfully treated the famous Italian mountaineer and explorer Carlo

Mauri. In recognition to his work, the Italians formed an Association for the Study

and Application of the Methods of Ilizarov (ASAMI). Ilivarov presented his

experience and successful treatment outcomes at the first Ilivarov surgical

symposium in New York in 1988.1 This symposium has inspired Dr. Joseph

McCarthy, a plastic and reconstructive surgeon working in New York, to apply

this technique in treating patients presented with cranio-facial deformities. In

1992, McCarthy et al. reported the first series of distraction cases applied in

human mandibles by using extraoral orthopaedic devices to treat four young

syndromal patients and successfully achieving mandibular bone lengthening

ranged from 18 to 24 mm.17




                                        13
2.0    Alveolar Distraction Osteogenesis (ADO) in Oral and Maxillofacial

Surgery


Alveolar bone resorption or bone defect can be caused by tooth loss, trauma,

periodontal disease, congenital anomalies or after tumour resection. In alveolar

bone deficiency, bone augmentation has shown to be necessary to allow

placement of implants at the edentulous area for patients to be able to reinstate

their functional and aesthetic balance thus improving their quality of life.18-21


Surgical bone augmentation technique for edentulous atrophic jaws should aim

to provide adequate bone volume to restore satisfactory alveolar ridge height and

width. Implantation on severe bony defects can create prosthodontic and

periodontal problems that may contraindicate the insertion of dental implants for

achieving optimal oral rehabilitation. The unfavorable crown to implant length

ratio may not just produce a less than ideal aesthetic result due to the long crown

appearance and difficulty to maintain good oral hygiene, but long prosthetic

crown component may also increase the risk of unfavorable bending moment

and implants being overloaded, thus increasing the risk of implant failure.22,      23



Currently, various surgical techniques can be performed in order to obtain an

optimal alveolar bone condition prior to implant placement. The commonly

accepted techniques are autogenous bone grafting, guided bone regeneration

and distraction osteogenesis.18, 19, 24-28


Alveolar distraction osteogenesis (ADO) was first reported in 1996, when Block

et al. experimented alveolar distraction in dogs.29 In that same year, Chin and



                                             14
Toth first applied alveolar distractor to treat alveolar defects in humans following

traumatic tooth loss.30


Even though autogenous bone grafting technique can be considered as a

reliable and safe technique, distraction osteogenesis has the advantage of not

needing a donor site thus reducing morbidity and operating time.19,                  28, 31



Theoretically, ADO can provide an unlimited vertical bone augmentation

restricted only by distraction dimension of the devices. It has been reported that

ADO has succesfully achieved a vertical bone gain that reached up to 20 mm.32,
33
     Apart from that, it is well documented that autogenous bone grafts commonly

produce unpredictable results due to irregular bone resorption during pre- and

post-implant placement and after prosthetic loading.19, 34, 35



ADO has the benefit of increasing bone length and simultaneous expansion of

surrounding soft tissues. The concomitant soft tissue expansion is also known as

neohistogenesis and is one of the major advantages of distraction osteogenesis

not able to be achieved by conventional bone augmentation techniques. This

procedure is widely accepted as safe, reliable bone formation, with low incidence

of major complications.24-28, 36



Most studies have demonstrated and recognized the procedure achieving

consistent    evidence    of   bone   augmentation    clinically,   histologically    and

radiographically, thus making it the most predictable surgical procedure for

vertical bone augmentation.24-28, 31, 36-38 Currently, ADO is extensively used as a



                                         15
treatment modality to treat alveolar bone deficiency in both mandible and maxilla

not only in native bone but in reconstructed jaws.23, 39-43


3.0    Indications


The recommended clinical indications of ADO as proposed by Urbani et al.

include moderate to severe atrophy of edentulous ridge, segmental deficiency of

the alveolar ridge that may compromise the aesthetic and functional aspects of

implant placement. The technique can also be indicated for gradual vertical

movement of ankylosed teeth and for gradual vertical shift of an osseointegrated

implant together with the surrounding bone and gingival tissue.44 Garcia et al.

recommended vertical alveolar distraction osteogenesis whenever the ratio of

required crown to bone height available for implantation is greater than one.45



In reconstructed jaw, ADO has been primarily indicated to correct the vertical

discrepancy between the reconstructed bone and the adjacent normal alveolar

ridge.23,   39, 41-43
                        Vertical distraction can be performed as a secondary surgery

aiming to gain bone height with sufficient thickness as reported by Hirota.46, 47 As

Hirota was the first to described ADO in a transplanted scapula; he emphasized

that due to the favorable thickness and bone quality of the scapula when

compared to other donor site, it is necessary to vertically increase the thicker

portion of the grafted bone to improve the bone mass for implant therapy.46, 47




                                             16
ADO is also indicated as a secondary procedure following post-reconstructive

resorption of non-vascularized bone grafts.39,      48, 49
                                                             Other indications of ADO

include insufficient soft tissue, unavailability of donor site and unfavorable donor

site condition for bone harvesting.40, 47


4.0    Principles of Alveolar Distraction Devices


The abundant vascularity for blood perfusion in the alveolar bone has made

distraction osteogenesis a possible technique for dentoalveolar region. The

technique involves a combination of minimal tissue reflection aiming for vascular

preservation followed by creation of surgical fracture and manipulation of the

bony fragments with a distractor device. The unique features of these devices

are made to allow transportation of a bone segment with simultaneous fixation.

These devices are developed based on the principles of the Ilizarov ring fixator

used by orthopedic surgeons today. By applying the Ilizarov’s tension-stress

principle   together   with   vascularity    preservation,    the   controlled   gradual

transportation of the bony segment will result in regeneration of new bone and

expansion of its overlying soft tissues.


The differences in anatomy and functions between the jaw bones and the long

bones have made direct application of Ilizarov’s distraction osteogenesis method

not appropriate and considered not ideal for the maxillofacial region. The

application of transcutaneous rods for alveolar bone augmentation is not practical

because of the interference with occlusal and aesthetic functions. Modifications

in both armamentarium and surgical technique are inevitable to make the devices



                                            17
more miniaturized and user-friendly for the oral region. External devices may

produce external scars thus significantly affecting facial aesthetics. For these

reasons, distraction devices need to be miniaturized in order to make it hidden

inside the mouth. The miniature devices are engineered and developed in high

precision to function optimally in intraoral environment and withstand the

masticatory forces without compromising the distraction aim. They also need to

be made of biocompatible materials to avoid any toxic or allergic reaction to the

patients and at the same time preventing other factors that may lead to

mechanical failure.


The development of miniature distractors that incorporate internal distraction

system has made transport of alveolar segments possible. These distraction

systems consist of three basic components: an upper member that can transport

the mobilized coronal segment of alveolar crest; a lower member that forms a

rigid base; and a movable component that can be activated. A distraction device

should allow gradual and controlled elevation of the transport bone segment

resulting in coronal displacement of the alveolar crest. This movement will also

slowly expand the overlying gingival soft tissue and re-establish the vestibular

sulcus.


As osteotomies are necessary to mobilize a coronal segment of the alveolar

bone, minimal tissue reflection and preservation of the mucoperiosteal flap is

essential in order to ensure the survival of the transport bone segment. A

chamber of regenerative tissue is established in the osteotomy gap that is




                                       18
perpendicular to the transport vector. The bony segments are gradually

transported away from each other by activating a central screw connected to the

activating rod. After achieving the desired extent of distraction, the fixation screw

can be left in place until bone healing occurs across the two bony segments. The

bone segments and the distraction regenerate will undergo a cascade of events

and as a result of the biological healing process, the volume of bone and soft

tissue will increase.


Latency period remains a subject of debate in different distraction osteogenesis

protocols. Nevertheless, most studies chose 7 to 10 days as their latency

period.27 The histologic events during latency period is similar to that illustrated in

fracture healing and can be described with phases of inflammation and formation

of granulation tissue.1 An adequate duration of latency period is also

recommended to enable mucosal wound healing of the intraoral incisions thus

making the tissue able to be put directly under tension.41-43


The optimum rate of distraction is one that allows bone formation during

lengthening with simultaneous tissue adaptation.50 The application of tension-

stress principle through gradual distraction of the soft callus and overlying tissue

will stimulate changes at both cellular and molecular level. The tensional stress

provides a micro-environment that allows the soft callus to remain at the center of

the distraction gap while allowing regular fracture healing at the periphery.1 Most

studies used a distraction rate of 0.5 to 1 mm per day.27 If the rate is too rapid, a




                                          19
non-union or fibrous union may occur while too slow activation rate may produce

premature bony union.


The duration of consolidation phase is a major factor that influences the overall

treatment time and primary stability of implants placed in the distracted bone.

The length of consolidation period is affected by a number of factors, which

include the intrinsic characteristic of bone healing process in alveolar bone and

the effect of functional loading by implants on the consolidated bone. Saulacic

and Turker have reported that a period of 12 weeks is sufficient for bone

maturation ready for dental implantation.27,     36
                                                      Most studies have demonstrated

that the procedure has a consistent evidence of bone augmentation clinically,

histologically and radiographically, thus making distraction a predictable and

reliable surgical method for bone augmentation.19, 27, 31, 32, 36, 51


5.0    Alveolar Distraction Devices

The devices dedicated for alveolar distraction are developed based on the vector

that directs the bone distraction movement and can be categorized into vertical,

horizontal (transverse) and bi-directional distraction devices. The device can be

intra-osseous or extra-osseous. In vertical distraction, the devices can also be

categorized either into non-prosthetic that require removal of devices after

completion of distraction or prosthetic devices that distraction mechanism and

dental implant are integrated into one composite device. All the available market

and published alveolar distraction systems to be presented in this article are

summarized in Table 1. In general, the devices available today have the following




                                           20
basic components: an active member for bone transportation, a distraction

mechanism and a passive member that acts as a base to support the activation

force of the distraction rod.

5.1    Vertical distractors

5.1.1 Intra-osseous devices

The application of LEAD system (Leibinger Endosseous Alveolar Distractor,

Stryker, Leibinger, Freiburg, Germany) in 5 cases of alveolar ridge augmentation

as reported by Chin and Toth in 1996 was the first series of alveolar distraction

demonstrated in humans.30 The intra-osseous distractor is made of titanium and

requires both upper and lower members of the device to be inserted horizontally

into the osteotomy gap (Fig. 1). The threaded distraction rod comes available in

17, 22 and 32 mm in lengths.



The system requires a trans-osseous alveolar bone preparation for insertion of

the distraction rod. It is advisable to use a temporary guidance prosthesis to

prevent vector malalignment of the transport segment from palatal or lingual

tissue pull.52 The exposed portion of the rod can be covered by temporary

denture that can indirectly stabilize the distractor. If the rod is exposed, the

interference by the rod on the surrounding structure may lead to masticatory

problems and deflection of the transport segment. The distractor can be activated

from 0.4 to 0.8mm (1 or 2 turns) per day. The device can in theory be removed

simultaneously at implant placement stage and any ingrowth fibrous tissue at the

distraction rod region needs to be removed.53 However, if the hole after distractor




                                        21
rod removal is too big for the planned implant diameter, the implants have to be

placed at a second stage.




       Figure 1. Application of LEAD device for vertical distraction of alveolar segment


The introduction of miniature intra-osseous distraction devices which are

modified from dental implant systems have the added benefit of design simplicity

and the ability to maintain the distracted segment orientation in the right

trajectory without any bone plate or screw. In 1999, Urbani et al.54 reported the

first clinical application of ACE Alveolar Osteogenic DistractorTM (ACE Surgical

Supply, Brockton, MA, USA) for mandibular ridge augmentation. This

endosseous distractor device is used for monofocal alveolar and small bone

distraction thus can be indicated to heighten a small depressed area by using a

single osteogenic distractor (OGD) device, or a defined regional span using

multiple OGD devices in regaining sufficient bone height prior to implant-

supported crown placement (Fig. 2). This distraction device is made with

precision technology from biocompatible titanium alloy (Ti 6AI-4V ELI) and has a

body with external threads that are similar with a conventional regular size (3.75

mm) dental implant, which makes the surgical drilling procedure similar to implant

placement.55




                                              22
The distractor body comes in 3 mm thread length (short body) or 5 mm thread

length (long body). It is designed with a variety of distraction pins for obtaining an

increased osteogenic bone mass reaching 16 mm at a distraction rate of 1 mm

per day. The base plug which will be stationary during active distraction has an

internal thread hole to allow the distraction screw to engage during activation

procedure. The implant can be inserted either using vestibular or crestal mucosal

incision. Paralleling pins are used to ensure parallelism when 2 or more

distractors are placed simultaneously. The thin distraction rod is placed inside the

device and protrudes only through the crestal mucosa. Two and a half turns

equal to 1 mm of bony distraction.55



The device can be retrieved easily without raising a mucoperiosteal flap unless

implants are placed simultaneously during the distractor removal procedure.

Since the device comes in 3.75 mm and 4 mm in diameter, a wider diameter

implant must be used accordingly to ensure primary implant stability. The base

plug can be left in situ due to its material biocompatibility.54 However, if the basal

plug interferes with the final implant position, it can be removed by threading the

system’s removal instrument onto the internal threads of the base plug.52




               Figure 2. Application of ACE alveolar osteogenic distractor for
               vertical alveolar distraction for a small alveolar bone defect



                                             23
In 2001, Urbani et al.44 reported the application of a Compact Alveolar Distractor

(CAD, Plan 1 Health Villanova, Udine, Italy), modified from the ACE alveolar

osteogenic distractor, to provide larger distraction distance (Figure 3). The

system comes in 6.2 mm (short) and 8 mm (long) in length and requires upper

vertical socket tapping using 3.75 mm tapping drill to allow insertion of the

device. The short and long device allows 7.5 mm and 10 mm vertical

augmentation, respectively. Should the transported bony segment develops a

lingual or palatal inclination, the distractor can be connected to an arch wire by

orthodontic spring to restore the correct vector orientation. Removal of the

distractor and insertion of 3.75 mm implant into the same hole can be done in

one procedure after 8 weeks of consolidation period to allow osseointegration if

the initial position corresponds to the final implant position. Otherwise, it is

advisable to delay the dental implant placement after 12 weeks of consolidation

phase.44



Groningen Distractor Device (GDD), introduced by the Groningen Expert Group,

is another intra-osseous system manufactured by KLS Martin.50 It was first

reported in 2000 by Raghoebar et al. in a pilot study involving 3 severely

resorbed edentulous mandibles.50 The miniature distraction device consists of

two long distraction screws, two extensions, one guide screw and two titanium

fixation screws to stabilize the extensions to the top of a transport bone segment

(Figure 4). The top distraction screw is hexagonal whereas the caudal end has a

smooth surface. When the distraction screw is activated, the cranial bone




                                       24
segment will be elevated. The distraction screws come in 14, 16, 18 and 20 mm.

However, it is necessary to have a mandibular bone height of at least 5 mm in

order to create a transport segment with a minimum of 2 mm thickness to prevent

fracture of the residual mandible. Implants insertion can be done simultaneously

during device removal using the same hole occupied by the distraction screws.




Figure 3. Compact alveolar distractor (CAD) for        Figure 4. The application of 2 distraction
vertical augmentation in small alveolar ridge          screws with one guide screw in Groningen
defect                                                 distraction system



Medicon (Medicon eG, Tuttlingen, Germany) developed 2 types of intra-osseous

distraction devices that can be applied for vertical alveolar bone augmentation.

Maastricht intra-osseous distraction screw is made of titanium and comes in 10,

15 and 20 mm in length (Figure 5a). Mainz distractor is a shorter intra-osseous

device that comes in 5, 7, 9 and 11 mm in length (Figure 5b). Both devices have

the advantages of being compact miniaturized distractors and eliminate the need

for plate fixation thus creating minimal reflection of soft tissue during surgical

insertion of distractors. Maastricht and Mainz distractors have 3.9 mm and 3.6

mm thread diameter, respectively. Standard implant protocol is followed for

device placement. Dental implants with a diameter of more than 3.9 mm

(Maastricht) and 3.6 mm (Mainz) can be inserted into the distractor holes. If more


                                                  25
than one device is used, a direction indicator or a guide for parallel drilling can be

used to achieve the vector parallelism. Osteotomy cut is made after one implant

hole is prepared. The device can be activated after placement to ensure the

transport segment movement is achieved without any tension (Figure 5c,d).56, 57

However, if the hole is infected or becomes larger thus the primary implant

stability is expected to be compromised, dental implants should be placed at

another site or insertion to be delayed until the bone is fully ossified.50, 58




                                                     A




                                                     B




                           C                                                     D

Figure 5. A, Maastricht distraction screw. B, Mainz intraosseous distractor system. C-D, The
application of multiple distractors for long span alveolar ridge defect using Maastricht (left) and
Mainz (Right) system. Note that both applications require parallelism to ensure smooth vertical
movement.



                                                26
5.1.2 Extra-osseous devices

The major advantages of extra-osseous system include minimal bone loss during

distractor fixation, direct visibility of the distractor vector and not contaminating

the dental implant insertion sites. However, the surgical procedure often requires

more soft tissue reflection thus increasing the risk of jeopardizing the blood

supply if not performed properly. The size of the devices occasionally cause

discomfort from pressing the surrounding oral soft tissue.



The use of TRACK device was first reported by Hidding et al. in 1999.59

Currently, The TRACK system (Tissue Regeneration Alveolar Callus Distraction

Koln, KLS Martin, Gebruder Martin GmbH, Tuttlingen, Germany) comes with a

variety of devices that can suit different anatomical requirements.60, 61 All the new

models consist an additional plate at the bottom end of the distractor to minimize

lingual or palatal tilting of the distraction vector during active distraction (Figure

6). Additional support plate can be fixed at the occlusal end of the device or

connects to the adjacent teeth to enhance vector control (Figure 6a).61



Micro TRACK comes in 6, 9 and 12 mm and is indicated for single ankylosed

tooth. TRACK 1.0 mm and TRACK 1PLUS are indicated for longer segmental

deficiency spanning 3 to 4 teeth. Both models come in 6, 9, 12 and 15 mm in

length. TRACK 1.5 mm is indicated for segment that consists of 3 to 4 teeth at

interforaminal or lateral region of the alveolar ridge while TRACK 2.0 mm is




                                         27
indicated for severely atrophic edentulous mandible with risk of secondary

fractures at the affected region. Both types have length of 10 and 15 mm.



All Martin titanium plates and screws are made of pure titanium or titanium alloy

(Ti-6AI-4V). As other titanium screws in this system are self tapping and require a

pilot hole, Martin’s Drill Free Screws can eliminate the need of drilling a pilot hole

thus enable insertion directly into the bone. The activation screwdrivers have

different activation distance per rotation according to different models. TRACK

1.0 is 0.3 mm per rotation, TRACK 1.5 is 0.5 mm per rotation and Groningen

distractor is 0.5 mm per rotation.61




                       A                            B

Figure 6. Diagram showing 2 variations of TRACK system used for alveolar distraction: A. Vertical
alveolar distractor with bone and tooth anchorage, B. Vertical distractor only with lower basal
bone anchorage



Verona distractor is an extra-osseous distractor developed by Medicon (Medicon

eG, Tuttlingen, Germany) using micro-fixation.62 This system consists of a

distraction rod with a 0.7 mm microplate on each side of the central rod for

fixation to the basal bone and then another microplate to the upper transport

segment (Figure 7).62 One full turn of its activation screwdriver equals to 0.3 mm

elevation of the transport segment. However, Verona system can only be



                                               28
activated up to 13 mm. The enclosed distraction mechanism prevents the active

component of the device from interfering with callus formation in the distraction

gap and trapping of surrounding soft tissue. As the system is indicated for vertical

distraction of the mandible, the residual bone should have at least 15 mm

horizontal, 8 mm vertical and 4 to 5 mm transverse dimension in order to allow

optimum device application and fixation.62




Figure 7. Verona mandibular distraction device with micro-plate fixation and maximum distraction
         height of 13 mm. The activation key is pictured in the centre.


Vertical Distraction Alveolar Ridge system (Walter Lorenz Surgical, Biomet Inc,

Jacksonville, FL, USA) is another extra-osseous device that comes with two

designs of single-tooth device and multi-tooth device (Figure 8a). The device has

3 available lengths of 10, 15 and 20 mm.63 The use of resorbable plate in this

system together with an external activation screw has been reported.53 This

distractor can be inserted through a conventional vestibular incision with

adequate mucosal reflection of the transport segment. The advantage of this

technique is that the distraction screw can be removed without making an

incision, leaving behind 2 resorbable plates. The resorbable plates (LactoSorb,

Walter Lorenz Surgical, Jacksonville, FL, USA) are expected to dissolve within

12 months and screw holes completely replaced with bone (Figure 8b).53




                                               29
                       A                                              B
   Figure 8. Vertical distraction system by Walter Lorenz. A, Multi-tooth device. B, Distraction
   rod with Lactosorb resorbable plate.



China (Cibei Medical Treatment Appliance Co. Ltd, China) has also developed a

device for alveolar distraction (CBX0504) which comes available in 8, 10, 12 and

15 mm in length (Figure 9). One full turn of its activation screw is equivalent to

0.4 mm.64 This device has an enclosed distraction rod to minimize soft tissue

irritation and consist of 2 horizontal plates with 8 screw holes each for fixation on

the bone segments.




                              Figure 9. Distractor device (Cibei Medical)

The other 2 commonly used vertical distractors are the Alveolar Distractor

(Synthes GmbH, Oberdorf, Switzerland) and MODUS® MOD 1.5 mm (Medartis

AG, Basel, Switzerland). These two devices will be discussed in details under

bidirectional distractors section.


                                              30
5.1.3 Tooth-borne devices

In vertical distraction, the adjacent teeth of the atrophic edentulous ridge may act

as an anchorage to the distraction mechanism. In this aspect, a tooth-borne

device has the advantage of not needing a surgical preparation and plate fixation

at the basal bone thus minimizing tissue manipulation and associated surgical

morbidity.



In 2000, Watzek et al. has developed a multidimensional device that used a

custom made abutment system with a cast framework that rests on the adjacent

teeth (Figure 10).65 As such, this tooth-borne device uses a pulling force when

compared to devices that employ a pushing force between upper and lower

members of the device via a distraction rod.53



Razdolsky reported the application of a tooth-borne device known as ROD-5

Distractor (Oral Osteodistraction, Buffalo Grove, IL) in 2001.66 This hybrid device

consists of a horizontal rod that is connected with two attachments, which need

to be bonded on the adjacent tooth surface. It can be considered as a tooth-

borne supported device and indicated for single tooth replacement. The device

uses only fixation wire to transport the coronal segment of the alveolar crest

(Figure 11).




                                        31
Figure 10. Transport segment can be distracted        Figure 11. Pulling force application with
in vertical and horizontal direction using the        the application of tooth-borne ROD-5
multidimensional device.                              device in single tooth defect


Tooth-borne device allows less invasive and simpler procedure for device

removal. However, it needs to be emphasized that the application of tooth-borne

distractor can only be indicated for small defect with healthy adjacent teeth. The

anchorage component on the tooth surfaces may also make the device a bit

bulky thus creating discomfort and interference to the surrounding soft tissue.



5.2     Transverse distractors

Other than vertical deficiency, insufficient width of alveolar bone also restricts

dental implant placement on an edentous alveolar ridge. Crest Widening

Distractor (Surgi-Tec) was designed by Zvi Laster and is used to expand the

narrow alveolar crest before dental implants can be inserted.38,              67
                                                                                   This device

consists of 4 arms, 2 on each side connected with guiding pins and an activating

screw (Figure 12A). It is indicated when the vertical height is sufficient but the

alveolar crest is too narrow and located too lingually or palatally (Figure 12B, C,

D). It is contraindicated when the ridge is not sufficient in height or when the

ridge has no cancellous bone in between the crestal cortical bones.


                                                 32
The procedure is normally performed under local anesthesia in two stages. The

first stage   involve a mucoperiosteal incision with raising of the buccal flap,

followed by the anterior, posterior and lower border bone cuts. Round bur can be

used to make a small trough along the crest. Bone cuts are made through the

trough to at least 10 mm in depth before the bone fragment can be loosened

using a thin osteotome. Bone cuts can also be made using a sagittal micro saw,

reciprocating scalpel saw, or piezoelectric ultrasonic bone cutter. Buccal plate

should be buccally fractured in “green-stick” manner before the wound is closed.

After one week, the device is tapped into the place percutaneously. A titanium

wire can be used to secure the device position by ligating a wire to an adjacent

tooth. A space of 1 mm between the device and the alveolar crest should be

made available for cleansing.



The activation is achieved by anti-clockwise rotation of the key. Distraction

begins 1 week later by turning the activating screw half turn twice per day. One

full turn equivalent to 0.45 mm. The activation can be done by the patient at

home with regular review by the responsible surgeon. The distraction device can

be removed after consolidation period and implants placement can either be

made simultaneously during the removal of the distractor or 2 weeks after

removal.38




                                       33
                                A                               B




                                C                                D
Figure 12 A. Laster Crest Widener, B. Pre-operative photo showing narrow alveolar ridge C. Intra-
distraction photo showing device application, D. Post-operative photo showing successful crestal
widening



The Titanium Steri-Plate System “Alveo-Wider” Mesh Plate and Screws (OKD

Okada Medical Supply Co. Ltd, Tokyo, Japan) is another crestal widener system

that consists of a malleable mesh plate, screws and a transosseous activation

screw.68 It is indicated for narrow edentulous alveolar ridge aimed for bucco-

lingual expansion prior to implant placement.



This system is different when compared to the crest widener developed by Laster

because it only consists of a piece of malleable mesh, which is fixed to the

buccal aspect of alveolar bone with titanium micro-screws (Figure 13a). The

malleable plate is advantageous to avoid any occlusal interference from the

opposing teeth.



The transport segment is created by performing two vertical osteotomies

connected with a horizontal osteotomy of the buccal plate. This segment is


                                               34
displaced labially when the threaded rod is activated thus creating an apical

horizontal green stick fracture (Figure 13b). Implants can be placed during

consolidation period or simultaneously at the time of the removal of the device.68




                     Figure 13a. Alveo-wider mesh plate and screws system




Figure 13b. Diagram showing distraction process starting from the osteotomy at the buccal plate
and followed by fixation of the malleable mesh with microscrews. Alveolar ridge is transversely
distracted upon activation of transosseous distraction screw. Implant is inserted when the alveolar
width is adequate.



Another alveolar crest widener that is available in the market was developed by

KLS Martin Group (Gebruder Martin GmbH & Co, Tuttlingen, Germany) which

uses the same design principle as the Alveo-Wider.60 The Horizontal Alveolar

Distractor system consists of a distraction screw and a simple straight plate

designed for application according to different span of a narrow alveolar ridge

segment (Figure 14a). The distraction screws come in different lengths of 4, 6, 8



                                                35
and 10 mm. The system also consists of a healing screw which is used during

latency period.



Both distraction and healing screws have one hexangular end which engages

with the activation screwdriver, a threaded part and a non-cutting end which

needs to be inserted slightly over the transverse osteotomy cut (Figure 14b). The

system uses one piece plate which comes in two designs of straight and angled

plates. Both plates are recommended to be fixed with 4 or 5 mm screws. One full

turn of the activation screwdriver is equivalent to 0.5 mm.60




                         A                                        B

Figure 14. A, KLS Martin straight plate system. B. Plate fixation on buccal aspect of alveolar ridge
and the diagram on the far right showing widened ridge when distraction screw is activated.


5.3     Bidirectional distractors

The bidirectional crest distractor (2D-CD) (SurgiTec NV, Bruges, Belgium) was

designed in 1998 to provide individualized correction of the horizontal position of

the transported segment simultaneously with vertical distraction (Figure 15a).

Horizontal correction related to occlusion and esthetics is important for

overcoming lingual or palatal shifting of the distracted segment.53




                                                36
The advantage of the bidirectional system is its ability to provide vertical

movement followed by horizontal movement to compensate for any lingual or

palatal deflection.69 The device can also be considered as small in size and

requires only small exposure via vestibular incision (Figure 15b). However, it

cannot be used in single tooth defect and is prone to rotational movements.53

The extent of vertical distraction is limited to 8-10 mm. It requires a re-entry

operation to activate another cycle of 8-10 mm if necessary. The extent of the

horizontal distraction is determined by a pair of transverse pins, which can cause

considerable discomfort to the lip due to the pins puncturing the lip.




                   A                                                B
Figure 15. Bidirectional crest distractor system. A, Distractor components and activation key. B,
The transport segment can be distracted in both vertical and horizontal direction.



The development of a multidimensional adjustment device reported by Watzek et

al. in 2000 has demonstrated that the axis of the device trajectory can be

adjusted during active distraction.65 This tooth-borne device has a custom made

abutment system with a cast framework that rests on the adjacent teeth that

makes it uses a pulley mechanism to exert a pulling force (Figure 10).53



The upper member is enclosed within the distraction segment. A vertical

activation rod protrudes through the mucosa and is guided by the cast frame on



                                                37
the adjacent teeth. A second activation rod is located on the buccal aspect. This

rod is activated after the distraction is initiated thus allowing the segment to be

distracted on both vertical and horizontal directions simultaneously. However,

this device has the disadvantage of the added interference on the lateral and

occlusal aspects by having 2 activation rods that may impinge the buccal mucosa

and the opposing dentition, respectively.53



One of the most crucial aspects in alveolar distraction is vector control. In

improving this vital component, Synthes (Synthes GmbH, Oberdorf, Switzerland)

has developed the Alveolar Distractor, an extra-osseous system with an

angulation mechanism wielded to the base plate, which can be adjusted intra-

operatively according to pre-operative plan for achieving vector control (Figure

16A, B). The distractor can be angled up to 52o towards the buccal or 32o

towards the lingual side (Figure 16C). The angulation mechanism must be

relocked by tightening the fixation screw after vector adjustment has been

made.70



The rigid base plate consists of optional screw holes next to the angulation

mechanism to allow safe anchorage. The additional screws provide extra vector

stability and device rigidity by preventing unfavorable distraction vector changes

from soft tissue pull. The plate is extended basally with an additional screw holes

for fixation to improve vertical stability of the system. This device has a fully

enclosed distraction body to minimize soft tissue irritation. The system comes in




                                        38
3 different sizes that allow 8, 12 or 16 mm distraction height. Each full clockwise

rotation is equals to 0.35 mm distraction distance and the direction of turning is

guided by an arrow marked on the activating key. The distractor can be removed

via the same vestibular incision after confirmation of bone regeneration in the

distraction gap during the consolidation period.70




                        A                           B                        C

Figure 16. Synthes alveolar distractor: A, Alveolar distractor device. B, Angulation mechanism of
                                                                                 o              o
           device (circled in red). C, Angulation can be adjusted up to 52 buccally or 32
           lingually



Another extra-osseous distractor that is commonly used for vertical alveolar

augmentation is MODUS® MOD 1.5 mm (Medartis AG, Basel, Switzerland).32, 71-
74
     Other than its good stability, the modular distraction design also allows good

adaptability to individual need for the augmentation of alveolar ridge74 (Figure

17a, b). The system has successfully incorporated an angulating mechanism to

the device and a thin rod that runs parallel with the activating rod is available to

enable post-operative vector change of the upper transport fragment if needed.

The system also allows the device to be mounted upside down and activated

extra-orally at the submandibular region using a detachable lengthening shaft as

reported by Adolphs et al.32 This is useful especially in cases of post-


                                               39
reconstructive surgery of the mandible where the device can be fixed through the

previous incision scar. As the system allows fixation of individual components

prior to the osteotomy, the threaded tube can be partially removed during

osteotomy thus facilitating the osteotomies to be made.32




                            A                                            B

Figure 17. Modus modular distraction system. A, Component can be assembled according to
specific indication. B, Close adaptation of device to the indicated segment can be achieved.



5.4     Implant distractors

5.4.1 Dental implant distraction devices

The introduction of integrated distractor and dental implant device is probably

one of the most exciting developments in alveolar distraction osteogenesis. The

concept was first introduced in 1997 when the system was developed at the

Department of Oral and Maxillofacial Surgery of Graz University.75 Other than

reducing the number of surgical procedures and its miniaturized device, the

handling procedure is simpler because of the axial access, which is similar to that

used in implant protocol. The distraction apparatus eliminates the need for plates

and screws due to the device’s ability to integrate with the basal and transport

segment. The implant application if performed accurately can reduce the overall




                                               40
treatment duration by not needing device removal and placement of a separate

implant thus allowing consolidation and progressing osseointegration.



In 1999, Gaggl et al.75 reported a successful application of 15 distraction implants

(SIS Trade Systems, Klagenfurt, Austria) on patients with alveolar ridge defects.

The system consists of a conical titanium screw with maximum diameter of 4.1

mm and the application follows conventional implant drilling protocol (Figure 18).

The endo-osseous portion of the implant surface is roughened by laser etching

treatment to increase the surface area. It has the property of self-tapping conical

screw and comes with available lengths of 7, 9, 11 and 13 mm.53 The implant site

preparation can be made through a tissue punch to remove the transgingival

mucosa    followed    by    segmental      osteotomy       via    vestibular     incision   as

demonstrated by Gaggl et al.76 This technique allows the distracted segment to

be pedicled to the lingual or crestal mucoperiosteum. The transgingival approach

also produces minimal scarring with good esthetic and functional outcomes.




                 Figure 18. Distractor implants developed by SIS Trade Systems. The
                 internal activation screw is secured once the distraction is complete.



Veriplant distraction device (EverFab, East Aurora, NY) is the first patented

combined dental implant distractor device.53 As this distractor acts as a



                                            41
permanent dental implant as well, a standard implant drilling protocol has to be

followed. It is important that knife edge ridges should be trimmed down during

site preparation. After the insertion of the device, the initial connecting member is

removed and replaced by a distraction rod (Figure 19). The rods are sequentially

sized in 5 mm increment and are interchangeable. An approximately 5 mm of rod

protrudes above the gingival level that allows fabrication of provisional prosthesis

to cover the site as well as to act as a guide thus assisting the determination of

distraction trajectory. The rod can be replaced with a longer one if more alveolar

height is desired. One turn is equivalent to 0.5 mm. After the distraction process

is completed, the distraction rod can be removed for the fixation of a connecting

component and cover screw. The upper and lower implant members are held

together with the final connecting component to form the implant.53




              Figure 19. Vertical alveolar distraction using Veriplant
              implant device for single alveolar ridge defect.



Robinson Inter Os Alveolar Distraction Device is also an internal distractor, which

serves as a permanent dental implant for restoring dentition comprising of a

cylindrical body, a base and a shaft (Figure 20a, b).77 The jaw has to be

predrilled with a hole of compatible size and depth for insertion of the device. An

osteotomy is made just beneath the predrilled hole. The implant selection is



                                              42
based on 4.1 mm in diameter and 8 mm in length. The minimum amount of bone

required is 12 mm (7 mm for the transport segment, 1 mm for osteotomy cut and

4 mm for basal bone). The width of the crest must be a minimum of 6 mm

because the current device has 4.1 mm diameter. Even though multiple devices

may be used in a single or multiple segments, patients need to be aware that the

devices may be removed and replaced by conventional implants if the implant

distractors fail to osseointegrate or the vectors are poor.53




                        A                                            B

     Figure 20. Robinson device: A, Application of multiple distractors for long span atrophic
     alveolar ridge. B, Further dental rehabilitation with implant supported bridge.



The 3i distraction device system (Implant innovations, Palm Beach Gardens, FL)

comes in 3.5 mm in diameter and 5 or 7 mm in length with a through-and-through

hole standard abutment screw, which has available length from 10 to 22 mm.53 It

is indicated when vertical bone augmentation of less than 10 mm is needed and

is inserted following a standard implant protocol. The preparation holes need to

be drilled to a depth of 9 mm to ensure that it passes through the horizontal

osteotomy. A 15 mm abutment screw is secured through the distraction implant

and the segment until it engages the basal bone. The screw is positioned until a




                                                43
notch is created in the basal bone so that a secure pivot point is established

(Figure 21).



This device can be easily removed should bone loss occur or should it become

dislodged during distraction procedure. A conventional 4 mm wide implant can be

placed at the same site and adjusted for the appropriate angulation if required.

Any additional implant distractors are to be placed within the same bone block

should have an exact parallelism. Otherwise, the bone piece may not be able to

be distracted to the full length of the implants. Parallel pins can be used to assist

in establishing parallelism. The osteotomies are made before the final drilling

steps, starting from horizontal cut of 7 to 8 mm below the crest and followed by 2

divergent vertical cuts toward the alveolar crest. Osteotomies are completed after

the device is inserted. A transfer abutment is removed before an activation pin is

inserted. The pin should be inserted to the point so that the transport segment is

distracted 1 mm in order to ensure that the pin is fully engaged to the foot plate.

Adequate stabilization period is required to allow osseointegration of the device

and consolidation of the distraction callus. The activation pin is removed prior to

the placement of an apical plug and healing abutment.53




                     Figure 21. The application of 3i devices for alveolar distraction.
                     Note that the apical portion of the devices is fixed in the basal bone.




                                             44
5.4.2 Implant distractor for reconstructive surgery

As ADO in reconstructed jaws is becoming more popular among maxillofacial

surgeons in providing optimum dental rehabilitation for post-ablative patients,

Zhang and Zhang in 2002 reported a one-stage application of custom made

Dental Implant Distractor (DID) device in a transplanted fibula bone graft. This

DID combines a dental implant and distractor together into a composite device

for reconstructive surgery involving 8 patients, who underwent mandibular

reconstruction with fibula flap (Figure 22).78 The study demonstrated that

mandibular resection, reconstruction and dental rehabilitation procedures are

feasible to be combined into a single surgery thus remarkably reduce the overall

treatment time.




                           Figure 22. DID for reconstructive surgery. Activation
                           screw (left) and distractor body with the base (right).
6.0   Conclusion

Alveolar distraction has gone through an enormous development since its first

introduction 15 years ago. The alveolar distractors available in the market

address to the nature of alveolar bone atrophy and fit to the surgeons’ preference

for reconstruction. As the treatment goals are influenced by the functions of the

specific device chosen, patients’ compliances should be considered in achieving



                                          45
a desirable and optimum result. The development of integrated distraction

implant devices can reduce the overall treatment duration by not needing device

removal and placement of a separate implant thus allowing consolidation and

osseointegration progressing simultaneously. However, the surgeons are still

concerned with the precision of the implant alignment as error in angulation is

amplified through distraction. With continuous research and further development,

it is expected that more improved designs and miniaturized version of distractors

will be available in the future market thus making distraction osteogenesis to

become the first choice in treating alveolar bone deficiency.




                                        46
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42.     Klesper B, Lazar F, Siessegger M, Hidding J, Zöller JE. Vertical distraction
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Craniomaxillofac Surg 2002;30:280-5.
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distraction of a free vascularized fibula flap in a reconstructed hemimandible: case report.
J Craniomaxillofac Surg 2000;28:20-4.
44.     Urbani G, Consolo U, Lombardo G. Alveolar bone distraction for implant
placement. In: Samchukov ML, Cope, J.B., Cherkashin, A.M., ed. Craniofacial
distraction osteogenesis. St. Louis: Mosby; 2001:423-32.
45.     Garcia AG, Martin MS, Vila PG, Saulacic N, Rey JMG. Alveolar distraction
before insertion of dental implants in the posterior mandible. Br J Oral Maxillofac Surg
2003;41:376-9.
46.     Hirota M, Mizuki N, Iwai T, Watanuki K, Ozawa T, Maegawa J, Matsui Y,
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reconstructed mandible for implant therapy. Int J Oral Maxillofac Surg 2008;37:481-3.
47.     Hirota M, Matsui Y, Mizuki N, Saito T, Watanuki K, Iwai T, Tohnai I.
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49.     Alkan A, Baş B, Inal S. Alveolar distraction osteogenesis of bone graft
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50.     Raghoebar GM, Heydenrijk K, Vissink A. Vertical distraction of the severely
resorbed mandible. The Groningen distraction device. Int J Oral Maxillofac Surg
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51.     Cano J, Campo J, Moreno LA, Bascones, A. Osteogenic alveolar distraction: A
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52.     McAllister BS, Gaffaney TE. Distraction osteogenesis for vertical bone
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55.     Ace. Ace Osteogenic Distractor. Ace Bone Grafting Catalog. In:26.
56.     Medicon. Distraction device "Model Mainz". Medicon Instrumente (Product
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57.     Medicon. Maastricht distraction screw system for reconstruction of the osseous
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62.     Medicon. Verona. Titanium distraction device. Medicon Instrumente (Product
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66.     Razdolsky Y, Dessner S, El-Bialy T. Correction of alveolar ridge deficiency using
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                                            50
70.     Synthes. Alveolar Distractor. Vertical bone lengthening of the alveolar ridge in
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concept in distraction osteogenesis. Medartis AG (Product Catalog). In. Basel.
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complications of alveolar distraction osteogenesis to enhance vertical bone height. Oral
Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:e7-e13.
73.     Erkut S, Uckan S. Alveolar distraction osteogenesis and implant placement in a
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74.     Gellrich NC, Suarez-Cunqueiro MM, Schon R, Hoffmann M, Schramm A.
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implant distractor: a new approach. Chinese Medical Journal 2002;115:1877-80.




                                            51
                Device                         Manufacturer                            Special feature

Vertical distraction
Intra-osseous
LEAD system                              Stryker Leibinger, Germany
ACE osteogenic distractor                ACE Surgical, USA
Groningen Device Distractor (GDD)        KLS Martin, Germany
Compact Alveolar Distractor (CAD)        Plan 1 Health Villanova, Italy
Maastricht distraction screw             Medicon, Germany
Mainz distractor                         Medicon, Germany


Extra-osseous
TRACK system                             KLS Martin, Germany              Variety of designs for different indications
Alveolar distractor                      Synthes, Switzerland             Vector control mechanism
Modus                                    Medartis AG, Switzerland         Individual fixation of device component
                                                                          Vector control mechanism
Verona                                   Medicon, Germany
Vertical distraction                     Walter Lorenz, USA               Can be used with resorbable plate
Alveolar distractor device               CIBEI Medical, China


Tooth-borne
Multi-dimensional (Watzek et al.)        Prototype                        Multi-dimensional
ROD-5                                    Oral osteodistraction, USA


Transverse distraction
Crest widener                            Surgi-Tec, Belgium
Alveo-wider                              OKD, Japan                       Malleable mesh and screws
Horizontal alveolar distraction          KLS Martin, Germany              Single plate and screws

Bidirectional
Bidirectional crest distractor (2D-CD)   Surgi-Tec, Belgium
Multidimensional (Watzek et al.)         Prototype
Alveolar distractor                      Synthes, Switzerland             Vector control mechanism
Modus                                    Medartis AG, Switzerland         Individual fixation of device component
                                                                          Vector control mechanism

Implant distractor
Veriplant                                EverFab, USA
Robinson Inter Os                        Robinson, USA
Distraction implant                      SIS Trade Systems, Austria
3i distraction device                    Implant innovations, USA
Dental Implant Distractor (DID)          Prototype (China)                For jaw reconstruction


                             Table 1. The spectrum of alveolar distraction systems




                                                             52
                      Part II:

Alveolar distraction osteogenesis for
 oral rehabilitation in reconstructed
      jaws: a systematic review

      Submitted to: Clinical Oral Implants Research




                           53
Introduction



Surgical reconstruction for extensive bone defects resulting from trauma,

infection or tumour resection involves a distinctive procedure striving for

replacement of lost tissues and regaining of lost functions. In jaw reconstruction,

the goals should aim for occlusal and aesthetic restoration of the bone, soft

tissues and teeth. Thus, the thickness, contour and mechanical properties of the

loss segment normally determine the choice of grafts (Schliephake & Hauseman

2007). Simultaneous surgical resection and microvascular reconstruction of

ablative defects are the current treatment of choice to provide hard and soft

tissue support, re-instate functional ability and at the same time restoring

aesthetical jaw contour.



As autogenous bone graft remains the gold standard for reconstruction of bone

defects, the survival of grafted bone cells is vital in order to create a mechanically

stable and biologically sound jaw bone. In this respect, the healing of non-

vascular and vascularized bone grafts differ greatly (Schliephake & Hauseman

2007) The vascularity of a recipient site represents the prime factor influencing

the success of non-vascularized bone grafts (Phillips & Rahn 1990). In contrast,

the survival of the bone forming cells in vascularized bone grafts depends on the

continuous perfusion following graft transfer.       Perfusion of a grafted bone

maintains the transplant viability, provides resistance against infection of the

grafts, allows survival of the grafted bone independently from the donor site




                                         54
conditions and at the same time generating a reliable bony union between two

bone segments (Schliephake & Hauseman 2007).



Common donor sites for non-vascularized bone graft include iliac crest, rib and

outer table of calvarium. For this technique, bone blocks can be harvested and

fixation is done using plates or screws to ensure firm fixation of the grafts and

intimate contact with the recipient site for successful healing. In some cases,

particulate bone grafts stabilized with titanium mesh can also provide a three

dimensional augmentation of the bone defects. However, it is well documented

that non-vascularized autogenous bone grafts has significant chance of infection

especially on large transplants and unpredictable long term bone resorption

(Cheung et al. 1994, Bell et al. 2002).



For vascularized bone graft, common donor sites include fibula, scapula, radius,

ilium and rib. Long has been the debate on the advantages and the drawbacks of

the donor bones. In term of length, radius has a considerable limitation while

scapula has limited width (Frodel et al. 1993) The need to turn the patients into

prone position has also made scapula not a favorable choice for reconstructive

surgery even though it has thicker cortical bone than other donor sites (Frodel et

al. 1993). It is often desirable that recipient site preparation and graft harvesting

to be performed simultaneously to reduce the ischaemic time so as to increase

the success of such major operations (Swartz et al. 1986, Hidalgo & Recow

1989).




                                          55
Even though the ilium has the advantage of having a considerable amount of

bone height and contour comparable with the mandibular body (Frodel et al.

1993), the vascular pedicle length is quite short and difficult harvesting limiting

the popularity of this graft. Additional morbidity includes gait disturbance, inguinal

hernia and lateral femoral cutaneous nerve injury (Colen et al. 1986, Kurz et al.

1989).



Vascularized fibula flap is the graft of many surgeons’ choice for reconstruction of

extensive mandibular reconstruction since its introduction by Hidalgo in 1989

(Hidalgo 1989). The fibula is easy to harvest and there is no long term functional

morbidity if correctly harvested. The appearance of the donor site after primary

closure is reasonable and the long vascular graft pedicle with large vascular

lumen makes it reliable. However, the limited vertical height of the fibula can

make further dental rehabilitation challenging (Bahr et al. 1998, Chiapasco et al.

2000).



In either non-vascularized or vascularized bone graft, the transplanted

edentulous bone is subjected to resorption overtime and any deficiency in bone

dimensions or soft tissues can later produce unfavorable conditions for further

dental rehabilitation (Nocini et al. 2004, Alkan et al. 2005, Holze et al. 2007). The

fabrication of removable denture depends on the adequacy of both mucosal and

alveolar bone support. The introduction of osseointegrated implants has now

proven to be the dental rehabilitation of choice for patients to restore their




                                         56
missing teeth and occlusal function following reconstructive surgery (Chang et al.

1998, Gurlek et al. 1998, Cheung & Leung 2003). However, the vertical

discrepancy between the reconstructed bone and residual bony ridge may create

problems that include insufficient sulcular depth and attached mucosa as well as

long crown to implant height ratio predisposing to fracture of the implant

connection. Owing to unfavorable periodontal status, patients will face difficulty to

optimize their oral hygiene thus increasing the risk of peri-implantitis and loss of

the implants in the long term (Chiapasco et al. 2000).



Distraction osteogenesis is a clinical tissue engineering method of bone

regeneration when the divided bone segments are being stretched with a

mechanical device. It was originally developed for long bone lengthening and

was first applied to the cranio-maxillofacial region in 1992 (McCarthy et al. 1992).

It was later extended to the regeneration of dento-alveolus and the technique is

called alveolar distraction osteogenesis (ADO). The earliest report where ADO

was applied to treat vertically deficient alveolar ridge was reported in 1996 (Chin

& Toth 1996).



Currently, ADO is extensively used as a treatment method to restore alveolar

bone deficiency in both mandible and maxilla. However, there are limited

publications on the applications of ADO in reconstructed jaws. This article aims

to comprehensively review all the published literature involving alveolar

distraction osteogenesis for reconstructed jaws, with particular emphasis on




                                         57
clinical indications, critical surgical factors, protocols and complications for oral

rehabilitation of reconstructed jaws.



Methodology



Online literature search of PUBMED was performed using keywords of ‘alveolar

distraction osteogenesis’ or ‘distraction osteogenesis’ with combination with other

keywords, such as ‘reconstructed jaw’, ‘vascularized bone graft’ and ‘free bone

graft’ from January 1996 to December 2009. The year 1996 was chosen as the

starting point of the search due to the first reported ADO case in 1996. The

searches confined to publications in English language.



The literature search was performed according to the guideline of PRISMA

statement (Moher et al. 2009). Phases of screening are summarized in Figure 1.

The inclusion criteria included cases of ADO performed in reconstructed jaws

either by vascularized or non-vascularized grafts. Cases with ADO performed in

the native jaw bones, distraction osteogenesis for jaw lengthening, multiplanar or

multifocal distraction procedure were excluded in this review. Due to limited

number of available publications, all articles related to this topic were included. A

total of 18 papers were identified. Full articles were retrieved before data

extraction and summarization were conducted.




                                         58
Excel worksheets were designed for listing the specific parameters for reporting.

The parameters include author, year of publication, number of patients, gender,

age, site and cause of defect, type of surgery, condition of residual alveolar bone

and donor site.



The parameters for distraction osteogenesis procedure include time interval

between primary reconstruction and placement of distractor, vertical bone gain

and distraction protocols (latency period, active distraction period, rate of

distraction and consolidation period).



The parameters for post-distraction period include insertion time of implants,

number of implants in the distracted bone and follow up period. Complications

that were associated with the techniques were also summarized in this review.



Results



A total of 43 cases of alveolar distraction osteogenesis in reconstructed jaws

were reported in 18 articles. The gender and age range of the patients are

summarized in Table 1.



The first 2 reported ADO in a reconstructed mandible were reported by Nocini et

al. (Nocini et al. 2000) and Chiapasco et al. (Chiapasco et al. 2000) in 2000.

There are only 5 studies that reported more than 3 cases (Klesper et al. 2002,




                                         59
Zhang & Zhang 2002, Kunkel et al. 2005, Eski et al. 2006, Lizio et al. 2009).

Klesper et al. (Klesper et al. 2002) in 2002 reported the largest patient cohort in a

single report with 9 patients whereas most of the remaining studies were single

case reports.



There were only 2 cases of ADO performed in the maxillary region (de Moraes et

al. 2009, Lizio et al. 2009), while the others were in the mandible. The jaw

defects were mostly resulted from malignancy, benign tumour or gunshot injury.

The defects were reconstructed mostly by vascularized fibula graft (33 cases),

vascularized scapula graft (2 cases) and non-vascularized iliac bone graft (8

cases). Most of the defects involved partially dentate residual ridges. All of these

data are summarized in Table 2.



ADO was primarily indicated to correct vertical discrepancy between the

reconstructed region and residual ridge in order to achieve adequate height of

the transplanted bone prior to implant placement (Chiapasco et al. 2000, Nocini

et al. 2000, Klesper et al. 2002, Zhang & Zhang 2002, Marchetti et al. 2002,

Fukuda et al. 2003, Levin et al. 2003, Nocini et al. 2004, Alkan et al. 2005,

Kunkel et al. 2005, Eski et al. 2006, Ortakoglu et al. 2006, Schleier et al. 2006,

Kürkcü et al. 2008, de Moraes et al. 2009, Lizio et al. 2009). The indications for

ADO are summarized in Table 3.




                                         60
The TRACK system developed by KLS Martin was the most common ADO

system used among the 18 studies (Nocini et al. 2000, Klesper et al. 2002,

Marchetti et al. 2002, Schleier et al. 2006, Hirota et al. 2008a, Hirota et al.

2008b). All distractors used for this method were intraoral devices, with mostly

extraosseous and 12 cases using intraosseous devices reported by Zhang

(Zhang & Zhang 2002) and Kunkel (Kunkel et al. 2005). Zhang reported the

application of a custom-made dental implant distractor (DID) device (Zhang &

Zhang 2002). These data are summarized in Table 4.



Most of the 18 studies applied a similar distraction protocol (Table 5). The vertical

bone height gained ranged from 6 mm to 15 mm. There was one patient reported

by Klesper at al. who underwent 2 separate ADO procedures at two different

sites at different age (Klesper et al. 2002). 15 studies mentioned further

rehabilitation with dental implants and 1 study by Eski et al. used removable

partial denture for oral rehabilitation (Eski et al. 2006). However, not all studies

that involved implants stated the name of implant system, timing of implant

insertion, primary stability and the time of loading. Nevertheless, most studies

reported their follow up period and these ranged from 2 to 81 months. The

available data are summarized in Table 6. It is noteworthy to mention that only

two studies conducted by Lizio et al. and Kunkel et al. reported long term bone

resorption and implant success rate (Kunkel et al. 2005, Lizio et al. 2009).




                                         61
Only few studies reported complications related to ADO (Nocini et al. 2000,

Klesper et al. 2002, Zhang & Zhang 2002, Fukuda et al. 2003, Kunkel et al. 2005,

Eski et al. 2006, Lizio et al. 2009). Complications were primarily reported from

studies that had more than 1 patient. The most common complications reported

in this review were infections and haematoma. These complications are

summarized in Table 7.



Discussion



The ideal aims of reconstruction and rehabilitation of the jaws following ablative

surgery are to restore bone continuity, provide adequate bone volume, restore

satisfactory alveolar ridge height and width, no graft resorption, restore soft

tissue defects, establish facial contour, and at the same time rehabilitate

masticatory and speech functions (Levin et al. 2003).



Severe vertical discrepancy between transplanted bone grafts and residual

alveolar ridges can create prosthodontic problems that oral rehabilitation by

dental implants is not possible. The unfavorable crown to implant height ratio

may not just produce a less than ideal aesthetic results due to the long crown

appearance and difficulty to maintain good oral hygiene, but long prosthetic

crown component may also increases the risk of unfavorable bending moments

and implant overload, thus increasing the risk of implants failure (Weischer et al.

1996, Chiapasco et al. 2000).




                                        62
Various techniques have been introduced in obtaining desirable alveolar height

at the reconstructed segments of the jaws. These include primary surgical

options of deep circumflex iliac artery (DCIA) flap (Frodel et al. 1993), double

barrel technique of fibula flap (Bahr et al. 1998), fixation of bone graft at the level

of residual alveolar process and secondary bone augmentation at the deficient

region (Kreusch et al. 1999). However, each technique carries considerable

benefits and setbacks. DCIA flap carries a considerable risk of donor site

morbidity (Colen et al. 1986, Kurz et al. 1989). The double-barrel technique of

fibula flap may not be suitable in a large defect as the length of bone segment is

normally not enough for duplication of the entire reconstructed segment

(Chiapasco et al. 2000). Moreover, this technique carries the risk of pedicle

thrombosis due to folding of the feeding vessels thus jeopardizing the viability of

the grafted vascularized bones (Chang et al. 1998, Nocini et al. 2000, Klesper et

al. 2002). By fixing the graft at the same level of residual ridge of the mandible,

the profile of the lower border will then be adversely affected with significant

facial distortion. Further reconstruction with new vascularized flap or onlay graft

is less favorable due to further morbidity and frequent refusal from patients after

already undergone a major surgical procedure (Kreusch et al. 1999, Chiapasco

et al. 2000).



This review shows that vascularized fibula is the most common flap used to

reconstruct segmental defects after tumour resection or severe trauma (Table 2).

Vascularized fibula flap has become the choice of many surgeons for




                                          63
reconstruction of extensive mandibular defect since it was introduced by Hidalgo

in 1989 (Hidalgo 1989, Hidalgo & Recow 1989). Other than providing an

extensive length of the bone graft, the fibula has a long pedicle and large vessels

that make it more reliable to reconstruct a long defect. It can also be harvested

as an osseo-fasciocutaneous graft thus allowing the reconstruction of both hard

and tissue defects. The flap is relatively easy to harvest with minimal long term

functional morbidity when compared to other major donor sites like scapula or

DCIA flaps and the appearance of the donor site after primary closure is

exceptionally good. Moreover, the technique allows a two team approach by

harvesting of the fibula during tumour resection thus reducing the operating time

and optimizing the success rate of graft survival following transplantation (Colen

et al. 1986, Hidalgo & Recow 1989, Kurz et al. 1989, Frodel et al. 1993, Chang et

al. 1998). However, the insufficient height of fibula may present a problem for

implant rehabilitation especially in patients with healthy residual dentition (Frodel

et al. 1993, Bahr et al. 1998, Chiapasco et al. 2000).



For this reason, ADO has the benefit of achieving concomitant increase in bone

height as well as expanding the volume of surrounding soft tissues. The soft

tissue expansion during bone distraction and elimination of bone harvesting from

other donor sites are the two major advantages of distraction osteogenesis.




                                         64
Indications

From this review, the primary indications for ADO are to correct the vertical

discrepancy between the reconstructed region and residual alveolar ridge after

reconstructive surgery and to achieve adequate vertical bone height prior to

implant placement (Table 3). Vertical distraction can be performed as a

secondary surgery that aims to gain bone height with sufficient thickness as

reported by Hirota (Hirota et al. 2008a, Hirota et al. 2008b). As Hirota was the

first to described ADO in a transplanted scapula, he pointed out the favorable

thickness and bone quality of scapula when compared to other donor sites.

However, it is still necessary to increase the thicker portion of the grafted scapula

by distraction in order to improve bone condition further to facilitate implant

placement (Hirota et al. 2008a, Hirota et al. 2008b).



ADO has been reported as a secondary procedure following resorption of a non-

vascularized bone graft (Nocini et al. 2004, Alkan et al. 2005, Kunkel et al. 2005).

Other secondary indications for ADO include insufficient soft tissue, unavailability

of other donor site and unfavorable new donor site (Hirota et al. 2008a, de

Moraes et al. 2009).



The indications of ADO for oral rehabilitation of reconstructed jaws do not differ

much from its indications in native bone. The recommended clinical indications of

ADO in native bone as proposed by Urbani (Urbani et al. 2001) include moderate

to severe atrophy of edentulous ridge, segmental deficiency of the alveolar ridge




                                         65
that may compromise the aesthetic and functional outcomes of implant

placement, narrow alveolar ridge, for gradual vertical movement of ankylosed

teeth and for gradual vertical shift of an osseointegrated implant together with the

surrounding bone (Urbani et al. 2001). Garcia et al. recommended vertical

alveolar distraction osteogenesis whenever the ratio of required crown height to

bone height available for implantation is greater than one (Garcia et al. 2003).



Surgical considerations

The time interval of applying ADO after reconstructive surgery in this review

ranged from 1 to 70 months. Nocini in his study reported that 1 year interval is

necessary to ensure complete bone regeneration (Nocini et al. 2000). In most

reconstructive cases, ADO was performed via an intraoral approach under

general anesthesia. Even though the graft needs to be exposed and requires

multiple osteotomies to achieve good contour, it is important to ensure that the

periosteum remained intact on the crestal and lingual surface of the

osteotomized bony segment for vascularization. Once the medullary vessels are

interrupted, the periosteum will become the only vascular supply for the entire

flap.



Klesper emphasized that favorable force was generated when the device

application is directly applied on the surface of the segments to be distracted. If

an integrated dental implant distraction device is used, cortical fixation is




                                        66
essential to prevent instability of the device during activation (Klesper et al.

2002).



The position and angulation of a distractor at an osteotomy segment is normally

estimated by extrapolation of vector from the residual dental arch or alveolar

ridge to reach the opposing dentition or prostheses. The distraction vector is

recommended to be perpendicular to the axis of the dental ridge thus avoiding

lingual inclination. The segment of bone to be distracted can be shifted from the

original site to facilitate a direct distraction vector while maintaining as much

contact with the non-distracted bone to achieve enough dimension of distraction

regenerate. If more than one distractor devices are being used, care had to be

taken for ensuring parallelism of the devices. The parallelism can be checked

using either directional rod or parallel drilling template.



The horizontal bone cut of ADO is recommended to be performed slightly tilted

lingually to maximize the vascularization of the area with soft tissue pedicle on

the top segment for transport. The vertical bone cuts on both sides were placed

in an angulated manner to achieve a trapezoid shaped bone segment in order to

prevent any undercut that may create bony hindrance during activation (Kunkel

et al. 2005). The junction between the horizontal and vertical cuts is

recommended to be rounded to minimize fracture of the basal bony segment

during the distractor activation.




                                           67
Most surgeons positioned the devices at the planned site before the osteotomy

cuts were made. The activation of the devices is recommended to be performed

immediately after distractor placement to check the vector of distraction and

freedom in movement of the transport segments. The osteotomized segments

should be repositioned achieving bone to bone contact until the site is ready for

active distraction.



The activation rod through the mucosa can create a portal of communication

between the inner part of the wound and the oral cavity, which can substantially

increase the risk of infection that jeopardizes the success of the procedure. In

minimizing this risk, tight suture closure should be performed and appropriate

oral hygiene measures should be emphasized to the patients. In our centre, we

instructed patients to clean the exposed distractor rod with Chlorhexidine

Gluconate 0.05% solution (Sterets® Unisept, Medlock Medical Ltd, UK) at the rod

mucosal junction, 3 times daily commencing at the latency period. The cleansing

should be performed before each activation of distractors at the activation period

and continue during the consolidation period until distractor removal.



In the study conducted by Eski (Eski et al. 2006), the device was placed via an

extraoral approach using the previous wound scar following gunshot injury. This

uncommon approach has eliminated any intraoral incision and minimized tissue

dissection. By having the activation rod through an extraoral wound, the risk of

oral bacterial contamination can be minimized but facial scar is expected. At the




                                        68
same time, the latency period can be reduced because the activation does not

need to wait until the intraoral mucosa has healed. The perforation of the rod

through the skin also functions as drainage of any wound exudate post-

operatively. By limiting soft tissue dissection, the vascularity of distracted

segments can be optimized (Eski et al. 2006). Wound cleansing similar to the

above protocol at the rod skin junction is important to minimize any infective

granuloma formation that affects the aesthetic of future scars.



ADO protocol

There is no standardized protocol universally used in the literature for vertical

alveolar distraction relating to its latency, rate, rhythm and consolidation period.

Most case series in this review selected 7 to 10 days as the latency period. This

latency length was recommended for good wound healing of the intraoral incision

(Nocini et al. 2000, Klesper et al. 2002, Eski et al. 2006). With good wound

healing, tissue can be placed under tension without any dehiscence. Only one

study conducted by Marchetti et al. started the activation immediately after the

placement of distractors (Marchetti et al. 2002).



The rate of distraction in all the studies was quite consistent to a range from 0.5

mm to 1 mm per day. This rate is comparable with other ADO studies in native

bone (Jensen et al. 2002, Cano et al. 2006, Chiapasco et al. 2007, Saulacic et al.

2008).




                                         69
The duration of consolidation phase is the major determinant of the overall

treatment period and primary stability of dental implants placed at the augmented

bone (Saulacic et al. 2008). Studies by Saulacic et al. (Saulacic et al. 2008) and

Turker et al. (Turker et al. 2007) indicated that a period of 12 weeks is sufficient

for bone maturation ready for dental implantation. In this aspect, most studies

used 3 months as a minimum consolidation period before removal of the devices.

However, in the study of Kunkel et al. (Kunkel et al. 2005), where intraosseous

distractors were used, the devices were removed together with the placement of

implants within 1 week after active elevation. In his study, ultrasonography was

used to assess the stability of the distracted segment.



This review indicated that fibula distraction managed to vertically increase the

alveolar segment up to 15 mm (Chiapasco et al. 2000, Schleier et al. 2006, Lizio

et al. 2009). Theoretically, there is no biological limit on the quantity of distraction

osteogenesis. The limitation lies in the design of the distractors. Clinically, the

transport segment is recommended to be placed in line with the adjacent native

alveolar height or to leave a minimal of 6 to 7 mm inter-alveolar height for the

crown prostheses. The thickness of the soft tissue should be taken into

consideration as well. The ADO has produced consistent evidence of bone

augmentation clinically, histologically and radiographically, thus making it a

predictable surgical procedure for vertical bone augmentation (McAllister 2001,

Zhang & Zhang 2002, Garcia et al. 2003, Chiapasco et al. 2006, Turker et al.

2007, Lizio et al. 2009). Furthermore, the distracted bone segment does not




                                          70
undergo significant remodeling like non-vascularized graft and this makes the

width of the upper segment predictable for implant placement. The cortical

thickness of the transplanted bone maintained thus enhancing primary implant

stability (Marchetti et al. 2002).



Only 4 studies from this review retrieved bone specimens for histological

evaluation (Nocini et al. 2000, Klesper et al. 2002, Zhang & Zhang 2002,

Marchetti et al. 2002). Nevertheless, the studies have demonstrated that there

was a presence of mature lamellar bone and viable osteoblastic activity, which

was found in all bone samples taken at the end of consolidation period.



Complications

ADO is technically sensitive and demands competent operators and highly

compliance patients to attain success of treatment. In this systematic review of

18 studies, few complications were reported. Most of the complications reported

were case series that consisted of more than three patients (Klesper et al. 2002,

Zhang & Zhang 2002, Kunkel et al. 2005, Eski et al. 2006, Lizio et al. 2009).

These complications include infection, haematoma, vector malalignment, basal

bone fracture and loosening of devices (Table 7). The types of complications

reported in this review were similar to complications that occurred in ADO

application on native bones as in other studies (Garcia et al. 2002, Enislidis et al.

2005, Bianchi et al. 2008, Saulacic et al. 2009).




                                         71
Lizio reported frequent hyperplastic growth around dental implants placed at the

augmented region probably due to lack of keratinized attached mucosa around

the implants combined with poor oral hygiene (Lizio et al. 2009). A number of

complications have also been reported by Li et al. (Li et al. 2008) in a study

involving distraction osteogenesis to lengthen mandibles, which have been

reconstructed with fibula, iliac and scapula flaps. Despite standard protocol being

followed, complications were reported in 3 out of 7 cases involving 2 mandibles

reconstructed with fibula and 1 case of mandible reconstructed with fibula and

scapula. The complications included device fracture, loose screws and loss of

bone (Li et al. 2008).



Resorption and implants survival rate

It is worth highlighting that only Lizio et al. and Kunkel et al. reported the rate of

bone resorption and the implants survival rate involving ADO in reconstructed

jaws (Kunkel et al. 2005, Lizio et al. 2009). Lizio et al. reported a mean peri-

implant bone resorption of 2.5 mm and implant survival rate of 94% after loading

(Lizio et al. 2009). In the study conducted by Kunkel et al. involving ADO in both

native mandibular and reconstructed bone that involved 28 implants, he reported

an overall 4-year 90% implant success rate. Out of 12 implants placed at the

reconstructed region that underwent ADO, 1 implant had more than 1.5 mm bone

resorption in the first year while another implant showed a 4.5 mm bone loss 3

years after implant placement (Kunkel et al. 2005).




                                         72
Although there were reported cases of bone resorption during peri-implant stage

in ADO, the incidence were consistent with dental implants placed in native and

non-augmented transplanted bones (Chiapasco et al. 2004, Nelson et al. 2006,

Chiapasco et al. 2007, Gbara et al. 2007, Perez-Sayans et al. 2008). The

survival and success rate of implants in ADO of native bones were comparatively

higher when compared to other conventional autogenous bony augmentation

techniques (Chiapasco et al. 2007, Bianchi et al. 2008). Kramer et al. (Kramer et

al. 2005) reported a success rate of 96.1% in a study assessing the efficacy of 55

dental implants placed in transplanted fibula free flap with observation period up

to 2.5 years.



A long term study reported by Holzle et al. (Holze et al. 2007) that involved 113

patients, who received free fibular graft following mandibular reconstruction,

demonstrated that fibular grafts show good long term stability. They concluded

that the rate of atrophy is significantly lower than that of edentulous or dentate

mandibular bone. Thus, making dental implantation into fibula bone grafts with

adequate bone height is as successful as when they are inserted into the

adjacent native mandibular bone.



Distractor design development

Various innovations and modifications have been made to further improve the

application of current alveolar distractors in solving various problems related to

the devices. The long treatment period may cause discomfort to the patients and




                                       73
difficulty in maintaining good oral hygiene. Communication between the oral

cavity to the deeper part of the wound through the activation rod area may

contribute to risk of infection (Kunkel et al. 2005, Saulacic et al. 2009). The

development of detachable activating rods can minimize this problem. Kunkel et

al. in their study inserted an additional internal sealing ring in their intraosseous

device, which can completely separate the internal parts of the distractor from the

oral cavity (Kunkel et al. 2005).



In term of vector control, Medartis (MODUS® MOD 1.5, Medartis AG, Basel,

Switzerland) and Synthes (Synthes GmbH, Oberdof, Switzerland) both have

manufactured devices that incorporate angulation mechanism, which can be

adjusted to control the vector trajectory of the transport fragment. In MODUS

system, the integrated thin rod that runs parallel with the activating rod enables

post-operative vector change of the transport segment whereas Synthes

distraction system allows vector adjustment to be performed only intra-

operatively (Medartis 2005, Synthes 2006).



Patients also need to be aware that ADO involves several surgical procedures

including removal of reconstruction plates, placement of distractors, removal of

devices, insertion of dental implants and implant abutment surgeries, thus

exposing patients to various morbidities and surgical risks from multiple

operations and long treatment time. The innovative development of the dental

implant distractor (DID) reported by Zhang and Zhang (Zhang & Zhang 2002)




                                         74
has remarkably shortened the treatment period. Intraosseous devices can also

minimize risk of infection by minimal soft tissue dissection and penetration of the

activation rod (Zhang & Zhang 2002, Kunkel et al. 2005). The utilization of a

reconstruction plate as the base for the device can eliminate the necessity to

remove the plate thus reducing the number of drilling and plating procedure that

can weaken the basal bone resulting in accidental fracture (Bousdras et al.

2009). However, the need of further horizontal osteotomy to the immediate

transplanted fibula bone, which normally requires segmentalization, is highly

technique sensitive and comes with unpredictable ischaemic risk to the bony

segments. This technique is recommended to be reserved for maxillofacial

surgeons with excellent microsurgical skill and distraction knowledge.



Kunkel et al. demonstrated that ultrasonography can be a useful tool to evaluate

the progress of remineralization and recorticalization of the distraction callus

(Kunkel et al. 2005). This additional evaluation method can be useful in

determining the actual consolidation period for a specific patient.



ADO in reconstructed jaws can enable rehabilitation of patients with dental

implants achieving similar success as native bone. The ADO devices require

meticulous techniques and experienced surgeons. Device failure and vector

alignment problem can occur creating a more complicated situation to be

managed thus risking of losing the grafted bone.




                                         75
Conclusion



This systematic review on ADO reveals few numbers of case series in this topic

and lack of randomized controlled trials. From the cohort studies, fibula graft was

more favored than other vascularized grafts for reconstruction of larger defects.

The primary indications for ADO in reconstructed jaws are to correct the vertical

discrepancy between the transplanted region and residual alveolar bone thus

achieving adequate vertical bony height prior to implant placement. Prospective

clinical studies with long follow-up periods would provide better perceptive on

ADO complications and whether the recent improvements in distractor designs

have solved the published complications associated with traditional distractors.

The development of integrated dental implant distractor has reduced the overall

treatment time of jaw reconstructive surgery. However, a larger number of cases

with this design are required to prove the reliability of distraction results. This

review shows that ADO in reconstructed jaws can produce consistent evidence

of bone regeneration with stable augmentation results clinically, histologically and

radiographically, thus making it a predictable surgical procedure for dental

implant rehabilitation.




                                        76
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                                         81
                 Article
                 identified                        Additional
Identification   through                           records from
                 PubMed                            other sources
                 search                                                            Keywords:

                 n= 165                            n=6                             "Alveolar distraction
                                                                                   osteogenesis" or
                                                                                   "distraction
                                                                                   osteogenesis" with
                                                                                   combination of
                                                                                   "reconstructed jaw",
                                                                                   "vascularized bone
                                                                                   graft", "free bone
                                                                                   graft"

                              Records after
Screening




                              duplicates
                              removed
                              n=62
                                                                                   Reasons:
                              Records                              Articles        1.Animal studies
                              screened                             excluded
                                                                                   2.Other anatomical
Eligibility




                              n=62                                 n=7             region

                                                                   Excluded full
                              Full text articles                   text articles   Exclusion criteria:
                              n=55                                 n= 37           1.ADO in native bone
                                                                                   2.DO for lengthening
                              Studies                                              3.Multiplanar and
                              included in                                          multifocal DO
Included




                              review
                              n=18



   Figure 1. Literature search and screening according to PRISMA statement (Moher et al. 2009)




                                                      82
                Age range        Male      Female      Total
                  < 20            3           6          9
                 20 - 29                      6          6
                 30 - 39                      4          4
                 40 - 49                      6          6
                 50 - 60             1        5          6
                  > 60               4        4          8
                  Total              8       31         39

                  Not
                                              4          4
               mentioned
                 Total                                   43

Table 1. Patients’ age and gender profile for alveolar distraction osteogenesis




                                83
Author             Year   Patient       Site                  Pathology          Cause of Defect   Residual ridge          Graft
                                                                                                      Partially
Nocini et al.      2000     1                                 Gunshot             Bone defect                             Fibula
                                                                                                      dentate

                                                           Chondroblastic            Tumour           Partially
Chiapasco et al.   2000     1                                                                                             Fibula
                                                           osteosarcoma             resection         dentate

                                                                                     Tumour           Partially
Marchetti et al.   2002     1                              Ewing Sarcoma                                                  Fibula
                                                                                    resection         dentate

                                                                                                      Partially
                                                          Ameloblastoma
                                                                                                      dentate
                                                            Odontogenic
                                                         calcifying epithelial                     Full arch defect
                                                                  cyst
                                                        Carcinoma of floor of
                                                                                                   Full arch defect
                                                             the mouth
                                                                                                      Partially
                                                             Keratocyst              Tumour
Zhang & Zhang      2002     8                                                                         dentate             Fibula
                                                                                    resection
                                                          Ameloblastoma                            Full arch defect

                                                          Carcinoma of left                           Partially
                                                               gingiva                                dentate
                                                        Carcinoma of floor of
                                                                                                   Not mentioned
                                                             the mouth
                                                                                                      Partially
                                    Not mentioned         Fibrous dysplasia
                                                                                                      dentate
                                                                 SCC


                                                                 SCC


                                                                 SCC


                                                                 SCC

                                                                                  Radiotherapy
                                                                 SCC               followed by
Klesper at al.     2002     9                                                                      Not mentioned          Fibula
                                                                                     tumour
                                                                 SCC                resection

                                                                 SCC

                                                                 SCC


                                                    *
                                                           Ewing Sarcoma
                                                    *

                                                                                                                            Non-
                                                             Odontogenic             Tumour           Partially
Fukuda et al.      2003     1                                                                                           vascularized
                                                              Keratocyst            resection         dentate
                                                                                                                      iliac bone graft
                                                                                     Tumour           Partially
Levin et al.       2003     1                           Desmoplastic fibroma                                              Fibula
                                                                                    resection         dentate
                                                                                                                            Non-
                                                         Trauma due to car                            Partially
Nocini et al.      2004     1                                                     Bone defect                           vascularized
                                                             accident                                 dentate
                                                                                                                      Iliac bone graft




                                                        84
                                                                                                                      Non-
Kunkel et al.          2004     4                            Tumour            Bone defect      Not mentioned     vascularized
                                                                                                                Iliac bone graft




                                                                                                                      Non-
                                                         Central Giant Cell                        Partially
Alkan et al.           2005     1                                               Curettage                         vascularized
                                                           Granuloma                               dentate
                                                                                                                Iliac bone graft

                                                                                                   Partially
Ortakoglu et al.       2006     1                            Gunshot           Bone defect                          Fibula
                                                                                                   dentate

                                                                                                   Partially
Schleier et al.        2006     1                            Gunshot           Bone defect                          Fibula
                                                                                                   dentate
                                                                                                   Partially
                                                             Gunshot           Bone defect                          Fibula
                                                                                                   dentate
                                                                                                   Partially
Eski et al.            2006     3                            Gunshot           Bone defect                          Fibula
                                                                                                   dentate
                                                                                                   Partially
                                                             Gunshot           Bone defect                          Fibula
                                                                                                   dentate

                                                                                                   Partially
Hirota et al.          2008     1                               SCC             Resection                          Scapula
                                                                                                   dentate

                                                                                                   Partially
Hirota et al.          2008     1                               SCC             Resection                          Scapula
                                                                                                   dentate

                                                                                                   Partially
Kurku et al.           2008     1                         Ameloblastoma         Resection                           Fibula
                                                                                                   dentate
                                                                                Resection +
                                                                              radiothreapy 2
                                                                               months after
                                                                                  implant
                                                                              placement due
                                                                              to SCC of vocal
                                                                                    cord

                                                                                Resection
                                                       Malignant tumours or                        Partially
Lizio et al.           2009     6                                               Resection                           Fibula
                                                       severe osteomyelitis                        dentate

                                                                                Resection

                                                                              Resection and
                                                                                 post-op
                                                                              radiotherapy

                                                                                Resection


                                                                              Curettage with                          Non-
                                                         Central Giant Cell                        Partially
De Moraes et al.       2009     1                                               peripheral                        vascularized
                                                           Granuloma                               dentate
                                                                                ostectomy                       iliac bone graft
* same patient
  SCC=squamous cell carcinoma

                  = mandible,         = maxilla


                        Table 2. Profile of available literatures on ADO for reconstructed jaws


                                                       85
                                  Clinical indications
Primary

Correction of the vertical discrepancy between the reconstructed region and
  residual ridge (Chiapasco et al. 2000, Nocini et al. 2000, Klesper et al. 2002,
  Zhang & Zhang 2002, Levin et al. 2003, Kunkel et al. 2005, Eski et al. 2006,
  Ortakoglu et al. 2006, Schleier et al. 2006, Kürkcü et al. 2008, de Moraes et al.
  2009, Lizio et al. 2009)

Inadequate bone height of transplanted bone prior to implant placement
  (Chiapasco et al. 2000, Nocini et al. 2000, Klesper et al. 2002, Zhang & Zhang
  2002, Marchetti et al. 2002, Fukuda et al. 2003, Levin et al. 2003, Nocini et al.
  2004, Alkan et al. 2005, Kunkel et al. 2005)

Secondary

Further enhance the thickness of a section of grafted bone to improve bone
  condition and facilitate implant therapy (Hirota et al. 2008a, Hirota et al. 2008b)

Resorption of transplanted primary bone graft (Fukuda et al. 2003, Nocini et al.
2004, Alkan et al. 2005, Kunkel et al. 2005)

Insufficient soft tissue (Klesper et al. 2002, Kunkel et al. 2005, Schleier et al. 2006,
Kürkcü et al. 2008)

Avoiding morbidity to new donor site (Nocini et al. 2004, Alkan et al. 2005)


                Table 3. Clinical indications for ADO in reconstructed jaws




                                     86
                                      ADO Systems
Extraosseous

MOD (Gebruder Martin GmbH & Co, Tuttlingen, Germany) (Chiapasco et al.
2000, Fukuda et al. 2003)
Modus ARS 1.5 (Medartis, Basel, Switzerland) (Alkan et al. 2005, Eski et al.
2006, Kürkcü et al. 2008)
TRACK (Tissue Regeneration by Alveolar Callusdistraction-Koln, Martin,
    Tuttlingen, Germany) (Nocini et al. 2000, Klesper et al. 2002, Marchetti
    et al. 2002, Schleier et al. 2006, Hirota et al. 2008a, Hirota et al. 2008b)
Verona (Medicon Instrumente®, Medicon eG, Tuttlingen, Germany) (Nocini
et al. 2004, Ortakoglu et al. 2006)

Intraosseous

Mainz'-Distractor (Medicon Instrumente®, Medicon eG, Tuttlingen,
   Germany) (Kunkel et al. 2005)
Dental Implant Distractor (DID) (Zhang & Zhang 2002)

        * ADO systems not mentioned in 3 studies


    Table 4. Various distraction systems used for ADO in reconstructed jaws




                                     87
                       Time of fixation
                                          Bone
                            after                 Latency   Activation      Rate     Consolidation
       Study                               gain                                                       Time of implant insertion
                       reconstruction              (days)     (days)      (mm/day)      period
                                          (mm)
                          (months)
Nocini et al.                15            11       7          22            0.5       3 months       No implant
Chiapasco et al.              3            15       7          20            1.0       3 months       During device removal
Marchetti et al.             12            12       0          12            1.0        70 days       6 weeks after device removal
Zhang & Zhang          Simultaneously      10       7          14            0.7      3-4 months      Not mentioned
                             12            10
                              9            12
                              9            12
                              9            10
                             14            12
Klesper et al.                                      8-9     9-12 days        1.0       12 weeks       During device removal
                             17            12
                              8            12
                              6*          10*
                             11*           9*
                              9            10
Fukuda et al.                11            13       7          13            1.0       9 months       During device removal
Levin et al.                 12            15       5          14            1.0       4 months       1 year after device removal
Nocini et al.                 3            11       7          N/A           1.0       3 months       During device removal
                                           6
                                                                                     Removal of distractors and placement of implants
Kunkel et al.          Not mentioned        7       4-5        N/A         0.5-1.0   within 1 week after 'active' elevation. Segmental
                                            9                                        elevation controlled by ultrasonography
                                           8.2
Alkan et al.                 48            13       7          N/A           1.0       3 months       Not mentioned
Ortakoglu et al.       Not mentioned       12       7          12            1.0       3 months       Not mentioned
Schleier et al.               1            15                        Not mentioned                    4 months
                             40            9        7
                                                                                                      No implant, rehabilitation with
Eski et al.                  70            13       7          N/A           1.0       12 weeks
                                                                                                      removable partial denture
                             60            10       5
Hirota et al.                18            9        6          N/A           0.5       4 months       During device removal
Hirota et al.                17            10       14         N/A           0.5       4 months       7 months
Kurku et al.                 12            10       7          N/A           1.0       3 months       During device removal
                                           15
                                           12
                                           12
Lizio et al.          11-38 (mean: 19)             7-10        N/A           1.0      3-4 months      2-5 months (mean:5 )
                                           15
                                           13
                                           15
de Moraes et al.              6             7       5           7            1.0         N/A          4 months after device removal
      * same patient


                  Table 5. Alveolar distraction protocol for patients with reconstructed jaws in 18 studies




                                                                     88
                                                                              Follow-up
                     Study       Year   Implants in distracted region
                                                                              (months)
              Nocini et al.      2000            No implant                 Not mentioned
              Chiapasco et al.   2000                3                      Not mentioned
              Marchetti et al.   2002                5                             6
                                                     3                            15
                                                     4                            15
                                                     4                            10
                                                     2                             8
              Zhang & Zhang      2002
                                                     4                             5
                                                     4                             3
                                                     2                             3
                                                     2                             2
                                                     4
                                                     4
                                                     4
                                                     4
                                                     4
              Klesper et al.     2002                                             24
                                                     4
                                                     5
                                               4* (posterior)
                                                4* (anterior)
                                                     4
              Fukuda et al.      2003                4                            24
              Levin et al.       2003                8                      Not mentioned
              Nocini et al.      2004                2                            12
                                                     3                            45
                                                     3                            42
              Kunkel et al.      2004
                                                     3                            37
                                                     3                            39
              Alkan et al.       2005                      Not mentioned
              Ortakoglu et al.   2006                3                            24
              Schleier et al.    2006                6                  Not mentioned

                                                                           22,17,7 months in
              Eski et al.        2006    Removable partial denture
                                                                           3 respective cases

              Hirota et al.      2008                4                            24
              Hirota et al.      2008                5                            24
              Kurku et al.       2008                3                            12
                                                     18
                                                     5                       17-81 months
              Lizio et al.       2009
                                                     7                        (mean:39)
                                                     5
              de Moraes et al.   2009                4                            12
                  * same patient


Table 6. Quantity of dental implants and follow up period among patients in 18 studies




                                                      89
                      Stage                                   Complications
                                             Device related             Non device related



  Intra-operative                                                   Nil



                                       *Infection (n=3) (Klesper    *Haematoma (n=4) (Klesper
                                       et al. 2002, Zhang &         et al. 2002)
                          Latency      Zhang 2002)
  Distraction phase




                                        Loose device (n=1)
                                       (Kunkel et al. 2005)
                                                                    Lingual transposition of
                                       Infection n=1 (Kunkel et
                         Distraction                               distracted segment (n=1)
                                       al. 2005)
                                                                   (Lizio et al. 2009)
                                                                   Fracture of basal bone (n=3)
                       Consolidation                               (Fukuda et al. 2003, Eski et al.
                                                                   2006, Lizio et al. 2009)
                                     Peri-implantitis around implants at distracted region
                                     (n=2) (Kunkel et al. 2005, Lizio et al. 2009)

                                       Bone loss (n=3) (Kunkel et al. 2005, Eski et al. 2006, Lizio
                                       et al. 2009)
  Post-distraction




                                       Occurrence of hyperplastic tissue around implants at
                                       distracted region (n=4) (Lizio et al. 2009)

                                       Gingival recession around implants at distracted
                                       region(n=1) (Lizio et al. 2009)

                                       Obliteration of vestibular fornix (n=1) (Nocini et al. 2004)


                                       Granulation tissue at half of distracted region (n=1)
                                       (Fukuda et al. 2003)
*Phase not mentioned


                      Table 7. Reported complications of ADO in reconstructed jaws




                                                    90
                      Part III:

Alveolar distraction osteogenesis for
   dental implants rehabilitation in
      reconstructed mandible

     Submitted to: Plastic and Reconstructive Surgery




                            91
Introduction

Extensive mandibular bone defect resulting from trauma, infection or tumour

resection requires a state-of-the-art mandibular reconstructive and rehabilitative

procedure as it implicates patient’s facial esthetics and oral function.

Simultaneous surgical resection and microvascular reconstruction of ablative

defects are the current treatment of choice to restore bone continuity, provide

adequate bone volume, restore satisfactory alveolar ridge height and width,

prevent graft resorption, restore soft tissue defects, establish facial contour, and

at the same time rehabilitate masticatory and speech functions (1).



For extensive mandibular defect, vascularized fibula bone flap has become the

choice of many surgeons for reconstruction since its first introduction by Hidalgo

in 1989 (2, 3). Fibula has the advantages of providing an extensive length of

bone graft and can be harvested with long pedicle and large vessels thus making

it a reliable graft to be used in a long defect. The fibula is easy to harvest, has no

long term functional morbidity if correctly harvested and the appearance of the

donor site after primary closure is reasonable.



The introduction of osseointegrated implants has now proven to be the best

dental rehabilitation option for patients to restore their jaw functions and facial

aesthetic following reconstructive surgery (4, 5). However, the insufficient height

of the transplanted fibula may create a challenging situation due to the creation

of a severe discrepancy between the transplanted bone and the healthy residual




                                         92
dentition (6, 7). With insufficient alveolar height, the unfavorable crown to implant

height ratio may not only produce a less than ideal aesthetic results due to the

long crown appearance and difficulty to maintain good oral hygiene, but long

prosthetic crown component may also increases the risk of unfavorable bending

moments and implant overload, thus increasing the risk of implants failure (7, 8).

Vertical discrepancy between the reconstructed bone and residual bony ridge

may also create problems that include insufficient sulcular depth and attached

mucosa. Owing to this unfavorable periodontal status, patients will face difficulty

to optimize their oral hygiene thus increasing the risk of peri-implantitis and loss

of the implants in the long term (7).



Although successful implantation on transplanted fibula has been reported (4, 9),

the long term prognosis remains uncertain due to residual vertical bone height

and surrounding soft tissue inadequacy. Techniques for obtaining desirable

alveolar height at the transplanted segments include primary surgical options of

deep circumflex iliac artery (DCIA) flap (10), double barrel technique of fibula flap

(6, 11), fixation of bone graft higher than the inferior border of the residual native

mandible (4) and secondary bone augmentation at the deficient region (12).

However, each technique carries considerable benefits and setbacks. DCIA flap

carries a considerable risk of donor site morbidity (13, 14). The double-barrel

technique of fibula flap may not be suitable for a large defects due to its limited

length of bone segment for duplication of the entire reconstructed segment (7).

Moreover, this technique carries an increased risk of pedicle thrombosis due to




                                         93
folding of the feeding vessels thus jeopardizing the viability of the grafted

vascularized bones (4, 15, 16). Fixation of the fibula at the same level of residual

alveolar ridge of the mandible produces a step deformity and lack of soft tissue

support to the profile of the lower border thus causing a significant facial

distortion. Further reconstruction with new vascularized flap or onlay graft is less

favorable due to further morbidity and frequent refusal from patients after already

undergone a major surgical procedure (7, 12). In either non-vascularized or

vascularized bone graft, the transplanted edentulous bone is subjected to

resorption overtime which can later produce unfavorable conditions for further

dental rehabilitation (17-19).



The introduction of distraction osteogenesis in oral and maxillofacial surgery has

embarked a promising development in surgical alveolar bone augmentation

procedures. Distraction osteogenesis is a clinical tissue engineering method of

bone regeneration when the divided bone segments are being stretched with a

mechanical device. It was originally developed for long bone lengthening and

was first applied to the cranio-maxillofacial region in 1992 (20). It was later

extended to the regeneration of dento-alveolus and called alveolar distraction

osteogenesis (ADO) and its first application to treat vertically deficient alveolar

ridge was reported in 1996 (21). The first 2 series of ADO in reconstructed

mandibles were reported by Nocini et al. (15) and Chiapasco et al. (7) in 2000.

Since its introduction, ADO has produced consistent evidence of bone




                                        94
augmentation clinically, histologically and radiographically, thus making it a

predictable surgical procedure for vertical bone augmentation (22-27).



Although ADO is extensively used as a treatment method to restore native

alveolar bone deficiency prior to dental implantation, there are still limited

publications on the applications of ADO in reconstructed jaws. This study aims to

comprehensively illustrate the outcomes of alveolar distraction osteogenesis in

cases of fibula reconstructed mandibles, with particular emphasis on clinical

indications, critical surgical factors, protocol, clinical outcomes, histological

evidence and its complications.



Methodology

Between February 2004 and May 2008, 5 patients under the care of the

Discipline of Oral and Maxillofacial Surgery, The University of Hong Kong,

underwent mandibular reconstruction with vascularized fibula bone graft followed

by alveolar distraction osteogenesis from September 2006 and July 2009. The

removal of the device was performed between October 2007 and October 2009.

All 5 patients underwent further dental implant rehabilitation between October

2007 and June 2010.

Patients

The study comprised of 2 males and 3 females patients ranging from 25 to 60

years old (mean age = 42.2 years old) at the time when fibula distraction

procedure was performed.




                                       95
Reconstruction Protocol

Prior to primary or secondary reconstruction, each patient underwent standard

protocol involving a comprehensive clinical and radiographic (plain x-rays and CT

scan) assessment. Doppler ultra-sound was performed to assess the patency of

the vessels at the fibula region. Each patient’s skull (Fig. 1A) and their fibula

stereomodel were fabricated for surgery was performed on the models. Surgical

guiding splints were made from the simulation surgery to ensure the accuracy of

the surgical cuts and fixation of the reconstructed segments (Fig. 1B and 1C).

Arch bars and reconstruction plate were pre-bent to achieve optimum stability for

the transplanted segment. The reconstructive surgical procedure (Fig. 1D, 1E

and 1F) was then performed following the pre-operative protocol adopted in our

centre in all the five patients.




                A                                B                          C




                D                                E                          F

Figure 1. Pre-operative and intra-operative phases in case 1: A, Fabrication of stereomodel. B,
Surgical simulation of mandibulectomy and fibula harvesting. C, Simulated fixation of fibula with
pre-bent reconstruction plate using surgical guiding acrylic splint. D, Intra-operative defect
following mandibulectomy. E, Fibula bone harvesting. F, Fixation of vascularized fibula flap



                                                96
Indication of ADO

The primary indication for ADO in all the reconstructed cases was to correct the

vertical discrepancy between the reconstructed region and residual alveolar ridge

in order to achieve adequate vertical bone height prior to implant placement.

Alveolar distraction osteogenesis protocol

All distraction osteogenesis procedures were done under general anesthesia by

the same surgical team (Oral and Maxillofacial Surgery, Queen Mary Hospital,

The University of Hong Kong). 1g Cefazolin and 4mg Dexamethasone was given

intra-vascularly on induction. Lidocaton 2% (1:80 000 adrenaline) was infiltrated

at the surgical area. Four cases involve submandibular incision through the

previous surgical scar and one case involved intraoral approach. Lower border of

the reconstructed mandible and reconstructed plate were identified, exposed and

removed (Fig. 2A). Subperiosteal dissection was performed to obtain adequate

visibility of the grafted fibula, but no mucoperiosteal dissection toward the crest

and on the lingual side was performed in order to preserve adequate blood

supply for the osteotomized bone segment.



The intra-oral distractor (Alveolar Distractor, Synthes GmbH, Oberdorf,

Switzerland) was adapted to the planned site before the osteotomy. For extraoral

approach, stab mucosal incision was made intra-orally to allow the distractor rod

to exit. Osteotomy cut was marked with bone marker (Fig. 2A). Horizontal cut

was made using bur and saw to separate the fibula reconstructed mandible with

at least 3 cm basal bone followed by two vertical osteotomy cuts made near the




                                        97
mandibular-fibula junction (Fig. 2B). Bone segment was mobilized and distractor

fixed in place with mini-screws to both the basal bone and the osteotomized

segment to the anterior part of mandible where distractor activation is easier (Fig.

2C). Vector guiding pin was applied in 3 cases where the fibula reconstruction

extends the molars and ramus to achieve the correct vector movement and

minimize rotation of this segment. The trans-osseous insertion of the pin was

assisted using the pre-fabricated surgical splint following the lag screw principle

with the pin angulation parallel to the distraction rod vector. The osteotomized

segment was then activated to check the direction of distraction and freedom in

movement (Fig. 2D). The transport segment then deactivated into its initial

position with bone to bone contact. Neck wound closed in 2 layers with Vicryl 4/O

and Nylon 5/O. Steri-strips applied and wound area dressed with micropore.

Intra-oral wound around was sutured with Vicryl 3/O.            All patients were

prescribed with post-operative antibiotic and analgesic for one week.




                      A                                    B




                                        98
                           C                                      D

Figure 2. Fixation of distractor in case 1: A, Reconstructed segment exposed and osteotomy
marking made. B, Vertical and horizontal cut at the fibula segment. C, Fixation of distractor and
vector guiding pin (arrow). D, Trial activation to ensure smooth distraction movement. Vector
guiding pin (arrow) in the distraction gap.



Patients were taught on how to activate the device. One full turn of the activation

screw was equivalent to 0.35 mm. Activation was done at home with weekly

review by the surgeon-in-charge. All patients underwent a latency period ranging

from 3 to 7 days to ensure the stabilization of the wound prior to activation. Active

distraction phase was commenced by having the distractor rod activated at the

rate from 0.35 to 0.70 mm per day. After distraction period completed, all patients

underwent a consolidation phase before the device was removed.



The patients were instructed to clean the exposed distractor rod with

Chlorhexidine Gluconate 0.05% solution (Sterets® Unisept, Medlock Medical Ltd,

UK), particularly at the rod mucosal junction, 3 times daily commencing at the

latency period. The cleansing was performed before each activation of distractor

at the activation period and continued during the consolidation period until

distractor removal.


                                               99
Removal of distractor and dental implants surgery

All patients had their distractor removed under general anesthesia after the

consolidation phase completed (Fig. 3A and 3B). Further oral rehabilitation with

dental implants was then planned. Bone availability was 3-dimensionally

assessed using cone beam CT scan and suitable implants were chosen. Surgical

splint was fabricated and used to ensure the implants were inserted at the right

position (Fig. 3C). Implants insertion was done following a standard conventional

implant protocol either during the distractor removal or in a separate surgery if

the distractor was removed earlier (Fig. 3D and 3E).

Bone biopsy

Bone biopsy was taken using a 3 mm trephine on the distracted fibula bone distal

to the last implant site immediately following the implant insertion (Fig. 3F). The

trephine was inserted from the occlusal fibula table vertically downward through

the distracted bone reaching the basal fibula bone.




                    A                                     B




                                       100
                        C                                            D




                        E                                            F

Figure 3. Removal of distractor and implants insertion in case 1: A, Exposure of device. B,
Removal of device with good bone regeneration at the distracted region. C, Application of surgical
wafer to confirm the implants location. D, Vector pins and its correlation with upper denture. E,
Insertion of implants. F, Bone biopsy taken distal to the last implant position using trephine
(arrow).



Peri-implant surgery

Vestibuloplasty with free attached gingiva graft from the opposing jaw was

performed in 3 patients at a separate procedure to obtain adequate sulcular

depth and keratinized tissue around the implants before dental prostheses were

fabricated.

Sectioning and staining of bone biopsy

The bone biopsy samples kept in their respective trephine drill were dehydrated

in a graded concentration of ethanol and resin embedded in glycolmethacrylate.



                                              101
Sections 100 µm thick were obtained using a Polycut E/ Ultramiller (Leica

SM2500 E, Nussloch, Germany). The sections were mounted on glass slides and

stained with toluidine blue for light microscopic examination.

Clinical and radiographic assessment

The clinical and radiographic records of all the patients were studied. Relevant

data were retrieved and analyzed in relation to the demographic, medical,

surgical, augmentation result, implant and prosthodontic aspects of each patient.

The patients were then invited to come for clinical assessment to evaluate the

current status of dental implant rehabilitation. All clinical and radiographic

measurements were performed by the same surgeon to eliminate inter-examiner

variation. Clinical assessment during distraction period included patient’s

complaint and thorough examination of the soft tissue and wound healing, signs

of infection, device function and tissue condition surrounding the exposed

activation rod.



As all the devices were fixed perpendicular to the alveolar bone and the vector

trajectory was positioned to match the opposing occlusion, slight inclination of the

distracted   segment    was    produced    thus   making    the   images    in   the

orthopantomogram (OPG) and relative measurement of vertical increment not

precise. As such, vertical increment of the distracted segment was calculated by

calculating the rate of distraction and total number of activation days. This

measurement was then compared to the vertical increment as shown in the

radiograph for validation.




                                        102
Following implants placement, the peri-implant status was evaluated according to

modified plaque index (MPI), modified bleeding index (MBI) and pocket depth

(PD). These 3 parameters will be recorded at four sites of each implant (mesial,

distal, buccal, and lingual/palatal). Pocket depth measurements will be performed

to   the   nearest   millimeter   using    a    plastic   periodontal   probe.   Serial

orthopantomograms and periapical radiographs were taken and compared to

assess for any bone resorption.



Excel worksheets were designed for listing the specific parameters for reporting.

The demographical parameters include gender, age, site and cause of defect,

type of surgery, donor site and the time interval between different surgical

procedures.



Result

This study involved 4 patients who had a segmental mandibulectomy due to

ameloblastoma and 1 patient due to osteoradionecrosis of the mandible. The

osteoradionecrosis patient has a history of tongue carcinoma and treated with

radical radiotherapy and chemotherapy. All 5 cases involved reconstructive

procedure with left fibula. Fibula reconstruction was a secondary procedure in

one case after a failed titanium-mesh tray reconstruction with posterior hip bone

graft due to infection and resorption. These data are summarized in Table 1.




                                          103
The timing of placement of distractor after fibula reconstruction ranged from 8 to

65 months (mean = 24.4 months). The latency period ranged from 3 to 7 days

(mean = 5.6 days). Distraction rate among the patients ranged from 0.35 mm to

0.70 mm daily and involved an activation period ranged from 16 to 36 days

(mean = 22.6 days). One patient had the distraction phase re-started after a

series of infection, bony hindrance and lingual tilting occurred during activation

phase. The vertical bone height achieved ranged from 11.2 mm to 17.5 mm

(mean = 13.58 mm). Consolidation period ranged from 6 to 27 weeks (mean = 15

weeks). All the data involving alveolar distraction protocol on each patient are

summarized in Table 2.



A total of 22 dental implants were placed in all the 5 cases. The highest number

of implants placed in a single distracted segment was 6 implants. Only one

patient had insertion of implants done simultaneously during removal of distractor

while others were performed in a separate procedure that ranged from 6 to 10

months (means = 8 months). Three cases required vestibuloplasty with a gingival

tissue graft before loading of the implants to obtain adequate vestibular depth

and keratinized tissue around the implants. Follow-up period starting from the

completion of alveolar distraction ranged from 8 to 32 months (mean = 19.6

months) while iImplant follow-up ranged from 1 to 33 months (mean = 14

months). All the data are shown in Table 3.




                                       104
Among the bone biopsy specimens, most were separated into fragments inside

the trephine due to the fragile cancellous bone. In one specimen, a continuous

bone specimen from the occlusal to the basal fibula bone was maintained.

Histological assessment confirmed smooth border lines are present between the

native cortical bone and the distraction regenerate with evidence of newly formed

bony trabeculae in the distracted area (Fig. 4 and 5).




Figure 4. Bone biopsy from case 2: Smooth border lines (yellow dotted lines) are shown between
the native cortical bones and the distraction regenerate (Figure 2). The distracted area is filled
with newly formed bony trabeculae (toluidine blue stain). Red (Fig. 5A) and orange (Fig. 5B)
boxes indicate 2 specific sites shown below in higher magnification. Bar = 1000 µm.




                             A                                B

Figure 5. A, Cortical bone at host area. B, New bone showing newly formed bony trabeculae.


Three patients (Case 1, 2 and 3) in this study completed their dental

rehabilitation with implants supported prosthesis. Our latest follow-up with these

3 patients showed that all implants placed were in healthy condition with minimal

gingival pockets ranged from 1 to 3 mm. There were also minimal plaque



                                              105
accumulation at the implants’ surface and no bleeding when periodontal probe

was passed along the mucosal margin adjacent to the implants.



Radiographic assessment among these 3 patients demonstrated that there was

minimal resorption rate at 1 year post-implant which ranged from 0.5 to 1.0 mm

in vertical. The resorption in case 1 stabilized when reassessment was

performed at 2 years follow-up after implants insertion. The clinical and

radiographical assessment data are summarized in Table 4.



The most common complication occurred was infection (Fig. 6A and 6B). Eight

series of infections associated with the distractor rod was recorded amongst 4

patients. Infections were managed by local debridement with Chlorhexidine

Gluconate 0.05% solution (Sterets® Unisept, Medlock Medical Ltd, UK),

particularly at the rod mucosal junction and antibiotic therapy. Bony hindrance

was detected in 2 patients (case 2 and 3) after the device were not able to be

activated at the early stage of active distraction phase. The bony obstruction was

removed using round bur during wound exploration under local anesthesia. One

patient reported of lingual tilting of the distracted segment (Case 3). The

transport segment was mobilized and the distraction rod was reconnected under

local anesthesia. Case 3 also had a fracture of basal bone during activation

phase (Fig. 6C). The fracture was fixed with 2.4 Unilock plate under general

anesthesia (Fig. 6D). All the reported complications and its management are

summarized in Table 5.




                                       106
                             A                                       B




                             C                                       D

Figure 6. Complications during ADO: A, Infection at the base of distractor. B, Pus at activation rod
         area. C, Fracture (arrow) of basal bone. D, ORIF at the fractured segments.


All the patients were happy with the outcomes of the surgical procedures not only

because of their facial aesthetic and mandibular contour was successfully

restored, but at the same time their masticatory and speech functions were also

rehabilitated. At the time of submission of this study, 3 patients have completed

their dental rehabilitation with implants-supported-bridges while the other 2

patients are still undergoing prosthodontic treatment. Clinical profiles and

radiographic images of different phases of each patient were shown in Figure 7,

8, 9, 10 and 11.




                                               107
     A                          B                      C                         D


Figure 7. Clinical and radiographic image for Case 1: A, Pre-operative phase. B, Post-operative
         18 months after reconstruction with fibula. C, Consolidation phase during ADO. D,
         Post-implants at 2 years follow-up.




                                               108
       A                           B                             C                       D



Figure 8. Clinical and radiographic image for Case 2: A, Post-marginal resection defect and
        recurrence of ameloblastoma at right mandible. B, Post-operative fibula reconstruction.
        C, Consolidation phase during ADO. D, Post-implants at 9 months follow-up.




                                            109
         A                             B                         C                         D

Figure 9. Clinical and radiographic image for Case 3: A, Pre-operative OPG showing mandibular
         ameloblastoma. B, Post-operative 6 months after fibula reconstruction. C, Consolidation
         phase during ADO. D, Post-implants at 5 months follow-up.




                                             110
     A                    B                     C                       D                    E

Figure 10. Clinical and radiographic image for Case 4: A, OPG showing mandibular
         ameloblastoma. B, Post-operative 30 months after mesh reconstruction shows bone
         resorption and collapsed mesh. C, Post-operative 5 years after fibula reconstruction. D,
         Consolidation phase during ADO. E, Post-implants at 2 months follow-up.




                                              111
               A                          B                  C                       D


Figure 11. Clinical and radiographic image for Case 5: A, Pre-operative. B, Post-operative 6
         months after fibula reconstruction. C, Consolidation phase during ADO. D, Post-
         implants at 1 month follow-up.




                                              112
Discussion

Alveolar distraction osteogenesis in reconstructed jaws is relatively a novel

technique. Our study illustrates 5 cases of ADO in fibula reconstructed

mandibles. For a similar study, the largest patients reported in a single cohort

case was by Klesper et al in 2002 (16) with 9 patients and to date, there are only

5 studies that reported of more than 3 cases (16, 25, 26, 28, 29).



The jaw defects in 4 cases reported in this study were due to ameloblastoma and

1 case was due to osteoradionecrosis. Most of the jaw defects reported in a

similar study were resulted from malignancy, benign tumour or gunshot injury.

Most of the reported defects were reconstructed with vascularized fibula graft.

Other than its advantage of being an osseo-fasciocutaneous graft for

reconstruction of both hard and tissue defects, the fibula flap is relatively easy to

harvest with minimal long term functional morbidity when compared to other

major donor sites like scapula or DCIA flaps and the appearance of the donor

site after primary closure is exceptionally good. Moreover, the technique allows

two team approaches by harvesting of the fibula during tumour resection thus

reducing the operating time and optimizing the success rate of graft

transplantation (2, 4, 10, 13, 14).



Distraction osteogenesis was primarily indicated to correct vertical discrepancy

between the reconstructed region and residual ridge in order to achieve

adequate height of the transplanted bone prior to implant placement in all of our




                                        113
patients. This indication is generally remains the primary indication for most

studies that involves reconstructed jaw which required ADO (1, 7, 15, 16, 18, 19,

25, 26, 28-35). Vertical distraction can also be performed as a secondary surgery

aimed to gain bone height with sufficient thickness as reported by Hirota (36, 37).

Hirota emphasized the necessity to increase the thicker portion of the grafted

bone in order to improve bone condition to facilitate implant placement (36, 37).

ADO has the benefit of achieving concomitant increase in bone height as well as

expanding the volume of surrounding soft tissues. The soft tissue expansion

during bone distraction and elimination of bone harvesting from other donor sites

are the two major advantages of distraction osteogenesis.



One of our patients had a primary reconstruction with titanium mesh and

posterior hip bone graft. However, after 3 years, the graft underwent resorption

thus resulting to the need of secondary reconstructive procedure. It is well

documented that non-vascularized autogenous bone grafts has significant

chance of infection especially on large transplants and unpredictable long term

bone resorption (38, 39). In this aspect, ADO has been indicated as a secondary

procedure following resorption of a non-vascularized bone graft (18, 19, 29). The

indications of ADO for oral rehabilitation of reconstructed jaws do not differ much

from its indications in native bone. The recommended clinical indications of ADO

in native bone as proposed by Urbani (40) include moderate to severe atrophy of

edentulous ridge, segmental deficiency of the alveolar ridge that may

compromise the aesthetic and functional outcomes of implant placement, narrow




                                       114
alveolar ridge, for gradual vertical movement of ankylosed teeth and for gradual

vertical shift of an osseointegrated implant together with the surrounding bone

(40). Garcia et al. recommended vertical alveolar distraction osteogenesis

whenever the ratio of required crown height to bone height available for

implantation is greater than one (23).



The mean time interval of applying ADO after reconstructive surgery in our study

was 24.4 months (ranged from 8 to 65 months). One patient had a longer period

of interval due to long orthodontic treatment prior to distraction procedure. Nocini

in his study reported that 1 year interval is necessary to ensure complete bone

regeneration (15).



In most reconstructive cases, ADO was performed via an intraoral approach

under general anesthesia. Four of our cases involved an extraoral approach via

the old scar. Even though the graft need to be exposed adequately, it is

important to ensure that the periosteum remained intact on the crestal and lingual

surface of the osteotomized bony segment for vascularization. Fixation of device

through an extraoral approach was also described in the study conducted by Eski

involving an incision through a previous wound scar following gunshot injury (28).



Extraoral approach has the advantage of eliminating the need of any wide

intraoral incision thus minimizing tissue dissection. However, a stab incision is

still required for the activating rod thus creating a portal of communication




                                         115
between the inner part and the outer oral environment which can increase the

risk of infection if oral hygiene is not practiced at an optimum level. If the

activation rod is penetrating through the extraoral wound, the perforation can

function as drainage of any wound exudates and at the same time minimizing the

risk of oral bacterial contamination. At the same time, the latency period can be

reduced because the activation does not need to wait until the intraoral mucosa

has healed (28). However, as facial scar is expected from this approach, wound

cleansing at the rod skin junction is important to minimize any infective

granuloma formation that may affect the aesthetic of future scars.



The position and angulation of a distractor at an osteotomy segment is normally

estimated by extrapolation of the residual dental arch and by guidance from the

opposing dentition or prostheses. The distraction vector is recommended to be

perpendicular to the axis of the dental ridge thus avoiding lingual inclination.

Occasionally, more than one device is needed in cases with a long segment to

be distracted. In such cases, care had to be taken for the parallelism of the

devices by confirming the right vector projection using either direction rod or

parallel drilling template. We used a vector guiding pin which was drilled trans-

osseously assisted with the pre-fabricated splint to achieve the correct vector

movement in 3 of our cases. The application of this pin follows the lag screw

principle with the pin angulation parallel to the distraction rod vector. Other than

assisting the transport segment towards the right trajectory, the application of the

guiding pin reduces the needs of having additional device thus reducing the cost,




                                        116
time of operation and reducing the risks of morbidity. The pin can be left in situ or

retrieved if the position interferes with the position of future implant. The pin can

also be trimmed down until the crestal bone level if it is found to be exposed.



We discovered bony hindrance that obstructs the vertical movement of the

transport segment during our exploration procedure in 2 of our cases. Other than

creating a slight lingually tilted horizontal bone cut at the transport segment to

maximize the vascularization of the area with lingual mucosa, the vertical bone

cuts on both sides should be placed in an angulated manner to achieve a

trapezoid shaped bone segment in order to prevent any undercut that may create

bony hindrance during activation (29). The junction between the horizontal and

vertical cuts is recommended to be rounded to minimize fracture of the basal

bony segment during the distractor activation.



The device should be placed at the planned site before the osteotomy cuts are

made to check the stability and accuracy of the placement. The activation of the

devices is recommended to be performed immediately after distractor placement

to check the vector of distraction and freedom in movement of the transport

segments before it is repositioned at its initial bone to bone contact prior to

wound closure.



Our cases followed a similar distraction protocol as described in other reported

ADO studies. There is no standardized protocol universally used in the literature




                                        117
for vertical alveolar distraction relating to its latency, rate, rhythm and

consolidation period. Most case series selected 7 to 10 days as the latency

period. This latency length was recommended for good wound healing of the

intraoral incision (15, 16, 28). Our mean latency period was 5.6 days (ranged

from 3 to 7 days). With good wound healing, tissue can be placed under tension

without any dehiscence. Our rate of distraction ranged from 0.35 mm to 0.7 mm

per day. These rates were quite consistent with other similar studies and

comparable with other ADO studies in native bone (27, 41-43).



The duration of consolidation phase is the major determinant of the overall

treatment period and primary stability of dental implants placed at the augmented

bone (42). Studies by Saulacic et al. (42) and Turker et al. (22) indicated that a

period of 12 weeks is sufficient for bone maturation ready for dental implantation.

In this aspect, our mean consolidation period of 15 weeks was comparable to

other similar studies which used 3 months as a minimum consolidation period

before removal of the devices. Histological examination of the bone specimens

from our patients showed that the distracted area was filled with newly formed

bony trabeculae and evidence of mature lamellar bone with viable osteoblastic

activity. The viable histological evidence was also reported by 4 other similar

studies involving ADO in reconstructed jaws (15, 16, 26, 34). As histological

evaluation is a reliable post-consolidation assessment procedure to confirm bone

maturity, Kunkel et al. demonstrated that ultrasonography can also be a useful




                                       118
tool during consolidation phase to evaluate the progress of remineralization and

recorticalization of the distraction callus (29).



The highest vertical increment achieved by fibula distraction demonstrated in our

study was 17.5 mm which was achieved in case 5. Due to the inclination of the

device during distraction phases, the relative vertical increment from the

radiograph may not produce a precise measurement. As such, measurement

was done by calculating the distraction rate and activation days for each patient.

However, we feel that it is noteworthy to mention that a 20 mm distractor was

used for case 5 because theoretically, there is no biological limit on the quantity

of distraction osteogenesis. The limitation lies in the design of the distractors. Our

mean vertical augmentation is 13.58 mm (ranged from 11.2 to 17.5 mm). This is

comparable to other studies which reported of vertical fibula distraction up to 15

mm (7, 25, 32). Clinically, the transport segment is recommended to be placed in

line with the adjacent native alveolar height or to leave a minimal of 6 to 7 mm

inter-alveolar height for the crown prostheses. The thickness of the soft tissue

should be taken into consideration as well.



Most of the complications reported in similar studies were in case series that

consisted of more than three patients (16, 25, 26, 28, 29). These complications

include infection, haematoma, vector malalignment, basal bone fracture and

loosening of devices. The types of complications reported in these papers were

similar to complications that occurred in our cases and in other reported cases of




                                          119
ADO application on native bones (44-47). The most common complication which

was reported in 4 of our patients was infection associated with the device.

Communication between the oral cavity to the deeper part of the wound through

the activation rod area may contribute to risk of infection (29, 44). In minimizing

this risk, tight suture closure should be performed and appropriate oral hygiene

measures should be emphasized. The development of detachable activating rods

can also minimize this problem. Kunkel et al. in their study inserted an additional

internal sealing ring in their intra-osseous device, which can completely separate

the internal parts of the distractor from the oral cavity (29).



Vector control and the choice of device are some of the crucial aspects in

alveolar distraction procedure. We used Synthes Alveolar Distractor (Synthes

GmbH, Oberdorf, Switzerland) in all of our cases as this system comes with an

angulation mechanism wielded to the base plate, which can be adjusted intra-

operatively according to pre-operative plan for achieving vector control. The

distractor can be angled up to 52o towards the buccal or 32o towards the lingual

side and the adjustment mechanism must be relocked by tightening the fixation

screw after vector adjustment has been made. The rigid base plate consists of

optional screw holes next to the angulation mechanism to allow safe anchorage.

The additional screws provide extra vector stability and device rigidity by

preventing unfavorable distraction vector changes from soft tissue pull. The plate

is extended basally with an additional screw holes for fixation to improve vertical

stability of the system. Most of the similar studies used the TRACK system




                                          120
(Tissue Regeneration Alveolar Callus Distraction Koln, KLS Martin, Gebruder

Martin GmbH, Tuttlingen, Germany) developed by KLS Martin (15, 16, 32, 34,

36, 37). The TRACK system comes with multiple designs that can be applied to

suit different types of alveolar defect. However, TRACK system does not allows

adjustment of vector, which generally led to lingual tilting of the transport

segment. So far, only MODUS® MOD 1.5 mm (Medartis AG, Basel, Switzerland)

and bidirectional crest distractor of SurgiTec (2D-CD, SurgiTec NV, Bruges,

Belgium) are available in the market that can allow adjustment of transport

segment vector intra-operatively as well as post-operatively. Some authors also

reported the application of intra-osseous devices for similar reconstruction cases

(26, 29). The development of the dental implant distractor (DID) reported by

Zhang and Zhang (26) has remarkably shortened the treatment period by making

the reconstructive and dental implant rehabilitation into one-stage surgery thus

reducing patients exposure to various morbidities and surgical risks from multiple

operations and long treatment time. Intra-osseous devices can also reduce the

risk of infections by little soft tissue dissection and minimal penetration of the

activation rod (26, 29). However, the application of multiple intra-osseous devices

require precise parallelism and occasionally require further horizontal osteotomy

to the immediate transplanted fibula bone thus making it a highly technique

sensitive and comes with unpredictable ischaemic risk to the bony segments.



Vestibuloplasty was performed in 3 of our cases to obtain adequate vestibular

depth and keratinized tissue around the implants. Lizio reported frequent




                                       121
hyperplastic growth around dental implants placed at the augmented region

probably due to lack of keratinized attached mucosa around the implants

combined with poor oral hygiene (25).



Our follow-up period immediately after removal of distractor ranged from 8 to 32

months while follow-up period after implants insertion ranged from 1 to 33

months. Only two similar studies conducted by Lizio et al. and Kunkel et al.

reported long term bone resorption and implant success rate (25, 29). Our latest

follow-up with the 3 patients who completed with dental prosthesis showed that

all implants placed have a healthy peri-implant status. Radiographical

assessment among these 3 patients also demonstrated minimal resorption rate

ranged from 0.5 to 1.0 mm at 1 year post-implant. Our 2 years follow-up in case

1 showed stabilization of the resorption rate. In the study conducted by Kunkel et

al. involving ADO in both native mandibular and reconstructed bone which

involved 28 implants, he reported an overall 4-year 90% implant success rate

and out of 12 implants placed at the reconstructed region which underwent ADO,

1 implant had more than 1.5 mm bone resorption in the first year while another

implant showed a 4.5 mm bone loss 3 years after implant placement (29). Lizio et

al. reported a mean peri-implant bone resorption of 2.5 mm with the implant

survival rate of 94% after loading (25). However, the survival and success rate of

implants in ADO of native bones were comparatively higher when compared to

other conventional autogenous bony augmentation techniques (27, 47).




                                        122
Conclusion

Distraction osteogenesis is a reliable surgical procedure that can be primarily

indicated to treat severe vertical discrepancy between the transplanted bone and

the residual alveolar bone prior to implant placement in reconstructed mandibles.

With an appropriate distraction protocol being followed, ADO can produce a

limitless vertical bone increment limited only by the size of the device. However,

the procedure has minimal risk of minor complication commonly to infection

associated with the device. There is still lack of high number of patients with long

term follow-up and randomized controlled trials in this field. Larger numbers of

studies with longer follow-up periods would provide better perceptive and

understanding of ADO outcomes and how to overcome its complications. Our

study demonstrated that ADO in reconstructed mandibles produced consistent

evidence of bone regeneration with stable augmentation results clinically,

histologically and radiographically, thus making it a predictable surgical

procedure prior to dental implantations.




                                        123
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                                                                                                   ADO and                 Distractor removal
                                                                                                                   ADO
                                                                            Reconstructive      reconstruction                and implant
Case   Age   Gender      Diagnosis               History           Site                                           phase                             Remarks
                                                                               surgery              interval                     interval
                                                                                                                 (weeks)
                                                                                                   (months)                     (months)


                                                                               Segmental
                                           Radiotherapy and                 mandibulectomy                                  Same time during
 1     51     Male    Osteoradionecrosis   chemotherapy for                        and               27            9          removal of
                                           tongue CA (T4N2)                  reconstruction                                    distractor
                                                                             with left fibula


                                                                               Segmental
                                           History of marginal
                                                                            mandibulectomy
                                           resection and
 2     40    Female    Ameloblastoma                                               and                8            31              8
                                           recurrence of after 3
                                                                             reconstruction
                                           years
                                                                             with left fibula


                                                                               Segmental                                                        Patient underwent
                                                                            mandibulectomy                                                      ORIF to fix basal
 3     35    Female    Ameloblastoma                                               and               11            31              8              bone fracture
                                                                             reconstruction                                                       during active
                                                                             with left fibula                                                   distraction period


                                                                                                                                                Patient underwent
                                           Resection and
                                                                                                                                                    orthodontic
                                           reconstruction with
                                                                             Removal of ti-                                                       treatment and
                                           Ti-mesh tray and
                                                                               mesh and                                                          fixation of bone
 4     60    Female    Ameloblastoma       posterior hip bone                                        65            15              6
                                                                             reconstruction                                                     anchor to upright
                                           graft. Resorption
                                                                             with left fibula                                                        and align
                                           occurred after 3
                                                                                                                                                 remaining teeth
                                           years
                                                                                                                                                prior to distraction

                                                                               Segmental
                                                                            mandibulectomy
 5     25     Male     Ameloblastoma                                               and               11            15             10
                                                                             reconstruction
                                                                             with left fibula


                                       Table 1. Patients’ demographic and time interval between different surgical procedures
                                                                                                                                                             Follow
                                                                                                                                Vertical
          Number                                      Vector                                                                                                up after
                                                                                          Latency      Distraction     Rate      bone      Consolidation
Case        of                     Site               guiding           System                                                                               device
                                                                                           (days)        (days)      (mm/day)   gained       (weeks)
          device                                        pin                                                                                                 removal
                                                                                                                                 (mm)
                                                                                                                                                           (months)



 1            1                                           1                                   6              16        0.70      11.2           6             32




                                                                                                             13        0.70
 2            1                                           1                                   7                                  12.6           27            24
                                                                                                             10        0.35


                                                                                                             7*       0.70*
                                                                       Alveolar               9*                                  Nil*
                                                                      Distractor,
 3            1                                                                                              22*      0.35*                     22            24
                                                                   (Synthes GmbH,
                                                                      Oberdorf,
                                                                     Switzerland)             3              21        0.70      14.7




 4            1                                                                               5              17        0.70      11.9           12            8




                                                                                                             14        0.70

 5            1                                           1                                   7                                  17.5           8             10
                                                                                                             22        0.35


       * First latency and activation phase, protocol re-instated after patient experiencing complications


                                                  Table 2. Summary of ADO protocol for each patient




                                                                                    128
        Number                                                                                                                            Follow-
                                                                                                       Additional
Case      of          Position                     System                         Bone biopsy                             Prosthesis        up
                                                                                                       procedure
       implants                                                                                                                          (months)
                                                                                                                               Implant
                                                                                                     Vestibuloplasty
 1        4         34,32,42,44       Branemark (Mk IV RP 4.0 x 13 mm)        Taken during stage I                            retained     33
                                                                                                     with palatal graft
                                                                                                                                bridge
                                                                                                     Vestibuloplasty           Implant
 2        6       35,34,32,42,44,45   Branemark (Mk IV RP 4.0 x 13 mm)        Taken during stage I    with gingival           retained     17
                                                                                                          graft                 bridge

                                                                                                     Vestibuloplasty           Implant
                                      Branemark (Mk IV RP 4 x 4.0 x 13
 3        5        33,31,42,44,46                                             Taken during stage I    with gingival           retained     17
                                           mm, 1 x 4.0 x 11.5 mm)
                                                                                                          graft                 bridge

 4        4         33,41,43,45       Branemark (Mk IV RP 4.0 x 13 mm)        Taken during stage I              In progress                 2

                                      3i Nanonite Tapered Certain Prevail
 5        3           44,45,46        (2 x 4.1 x 13 mm, 1 x 4.1 x 11.5        Taken during stage I              In progress                 1
                                      mm)




                                      Table 3. Details of dental implants and follow up period among patients




                                                                            129
                                Clinical assessment at latest follow up                                Radiographic


                                                                                                               Resorption
Case   Implant     Mobility      Pocket         Modified      Modified                                         Mesial-Distal
                                  depth          Plaque       Bleeding     Peri-implant                           (mm)
                                 M-D-B-L         Index         Index       radiolucency
                                  (mm)         (Score 0-3)   (Score 0-3)                       3             6
                                                                                                                        1 year       2 years
                                                                                             months        months

         34                       2-2-2-2          1             0                               0-0         0.5-0      0.5-0.5      0.5 -0.5
         32                       2-2-2-2          1             0                               0-0         0.5-0      0.5-0.5      0.5-0.5
 1                     0                                                       No
         42                       3-3-3-3          2             1                               0-0        0.5-0.5     0.5-1.0      0.5-1.0
         44                       3-3-3-3          2             1                               0-0        0.5-0.5     1.0-1.0      1.0-1.0
         35                       2-2-2-2          0             0                               0-0        0.5-0.5     0.5-1.0
         34                       2-2-1-2          0             0                               0-0        0.5-0.5     1.0-1.0
         32                       3-2-1-3          0             0                               0-0        0.5-0.5     1.0-1.0
 2                     0                                                       No                                                      N/A
         42                       3-1-1-3          0             0                               0-0        0.5-0.5     1.0-0.5
         44                       1-1-1-1          0             0                               0-0         0-0        0.5-0.5
         45                       2-3-2-1          0             0                               0-0         0-0        0.5-0.5
         33                       2-1-3-2          1             0                               0-0         0.5-0      0.5-1.0
         31                       3-3-2-2          0             0                               0-0         0-0        1.0-0.5
 3       42            0          2-2-2-2          0             0             No                0-0         0-0        0.5-0.5        N/A
         44                       2-1-1-1          0             0                               0-0        0.5-0.5     0.5-1.0
         46                       2-2-1-1          0             0                               0-0          0-0       1.0-1.0
         33
         41
 4                                 Implants still embedded                     No                                     N/A
         43
         45
         44
 5       45                        Implants still embedded                     No                                     N/A
         46

        M-D-B-L = Mesial-Distal-Buccal-Lingual                              N/A= Not available

        Modified Plaque Index                                               Modified Bleeding Index
        0 - No detection of plaque                                          0 - No bleeding when periodontal probe is passed along
        1 - Recognized by running a probe across                                 the mucosal margin adjacent to the implant
            smooth marginal surface of implant                              1 - Isolated bleeding spots visible
        2 - Can be seen by naked eye                                        2 - Blood forms a confluent red line on mucosal margin
        3 - Abundance of soft mater                                         3 - Heavy or profuse bleeding


        Table 4. Clinical and radiographic assessment among 5 patients with dental
                implants after fibula distraction




                                                                  130
Case      Phase                    Complication                                                  Management


 1                     Nil                                    Nil
                       Infection                              Antibiotic and local debridement
          Active       Submerged of activation rod
        distraction                                           Exploration of wound and removal of bony hindrance under local anasthesia
 2                     Bony hindrance

       Consolidation   Infection                              Antibiotic followed by removal of distractor

       Post-implant    Infection                              Antibiotic and local debridement

                       Basal bone fracture                    ORIF with 2.4 Unilock plate with 5 locking screws
          Active
        distraction    Bony hindrance                         Exploration of wound and removal of bony hindrance under local anaasthesia

 3                     Lingual tilting of transport segment   Mobilization of transport segment, reconnection of activation rod

                       1st serie of infection                 Antibiotic and local debridement
       Consolidation
                       2nd serie of infection                 Antibiotic and local debridement followed by removal of distractor

          Active
                       Infection                              Antibiotic and local debridement
 4      distraction
       Consolidation   Infection                              Antibiotic and local debridement followed by removal of distractor

                                                              Incision and drainage, local debridement, antibiotic prescription
 5     Consolidation   Infection
                                                              Early removal of distractor and rigid fixation


                             Table 5. Reported complications and its management




                                                              131

								
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