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Tooth loss and implant replacement

VIEWS: 199 PAGES: 23

									      INVITED REVIEW
                                                                                        Australian Dental Journal 2000;45:(3):150-172

Tooth loss and implant replacement
P. J. Henry*

      Abstract                                                       However, dentists are now confronted with a
      Osseointegrated dental implants are increasingly             variety of commercially available implant systems
      used to replace missing teeth in a variety of                and a kaleidoscope of techniques and protocols. As a
      situations ranging from the missing single tooth to          result, many practitioners are cautious, confused and
      complete edentulism. The implant possibility must
      be carefully considered because treatment
                                                                   concerned as to what is in the best interests of
      involves extended time frames, considerable                  patient care. This review, based on 20 years’
      expense and is not without risk. Accordingly, treat-         experience and development in Western Australia,
      ment-planning decisions should have an evidence-             will review the current state of the art and make
      based strategy with appropriate risk assessment.
      Implant systems need to be adequately tested                 scientifically based recommendations for case
      before they are released for general use and suc-            selection.
      cess rates should be assessed from peer review
      scientific publication data and not commercial pro-          Risk assessment and evidence-based treatment
      motional literature. It is the responsibility of the
      dentist to ensure the patient is educated so an                 Historically, the field of dental implantology has
      informed decision can be made on difficult treat-            been more akin to an art form than a scientifically
      ment alternatives. The clinical decision making              based discipline. The advent of the concept of
      process must respect the issues to assure quality
      of care and reduction of liability for negligent care.       osseointegration resulted in the dental establishment
      Today, the three-unit fixed bridge can no longer be          eventually accepting the dental implant as a
      considered as the standard of care for restoration           predictable clinical reality for long-term use in
      of a single missing tooth. The evidence has accu-            selected cases. This was because osseointegration, ad
      mulated that the single tooth implant supported
      replacement is more conservative, more cost-effec-           modum Brånemark, emerged from a basic science
      tive and more predictable with respect to long-              laboratory background and was subsequently
      term outcome in uncomplicated cases.                         exhaustively evaluated in animal studies, limited
      Key words: Osseointegration, dental implants, evi-           pilot studies and controlled multicentre long-term
      dence-based dentistry, tooth replacement, training and       prospective clinical trials before eventually being
      education.                                                   released for clinical use. The clinical users were
      (Received for publication June 2000. Accepted July           required to undergo formal training and education
      2000.)                                                       in all aspects of both the software and hardware
                                                                   associated with this new modality. Perhaps the most
                                                                   salient feature of the development was the fact that
Introduction                                                       the basic science laboratory background was
  Osseointegrated implants were introduced in                      medically based bioengineering and the dental
Australia in 1981 when university replication studies              involvement in the project was irrelevant and non-
on the rehabilitation of the edentulous mandible ad                existent in the beginning.
modum Brånemark were conducted simultaneously                         The original basic science development of the
in Perth and Sydney. Subsequently, the application                 1970s led to refinement and application of the
of osseointegrated implants for all types of                       surgical techniques, resulting in predictably high
edentulism ranging from the single missing tooth                   success rates achieved in widespread clinical
through to total edentulism has occurred.                          applications in the 1980s. In the 1990s, there has
Furthermore, implant treatment has become                          been an emphasis on dental implant aesthetics
increasingly accepted by the dental community and                  together with expanded clinical applications, ranging
has been included in the curriculum of most dental                 from the missing single tooth to complex multi-
schools.                                                           disciplinary management of the extensive orofacial
                                                                   cancer defect, in orthodontics, and finally under
*Prosthodontist, the Brånemark Center, Perth, Western Australia.   controlled circumstances in specific areas of
150                                                                                             Australian Dental Journal 2000;45:3.
paediatric dentistry. Thus, the area of applied           Table 1. Cumulative success rates (%) of
osseointegration is seen as the fastest growing area of   implants according to type of treatment
clinical practice. Unfortunately, as is the case with                                             Maxillae   Mandibles
many things growing too fast, it is now almost out of     Single-tooth restorations                96.6        100
control.1                                                 Partially edentulous fixed bridgework    92.0        94.2
                                                          Complete edentulous bridgework           86.8        100
   Society is increasingly challenged by the need for     Overdentures                             73.4        96.5
accountability. Dentistry in general and implant
dentistry in particular are no exceptions to the rule.
Fundamental to accountability are the concepts of
risk assessment and evidence-based treatment              Clinical applications of implants: current
strategy. These issues must be addressed seriously if     practice and future directions
dentistry is to reflect a scientific profile within the      Contemporary clinical experience is based on a
healthcare community. The clinical decision making        foundation of international, controlled, prospective,
process must respect these issues to assure quality of    long-term multicentre clinical trials. The cumulative
care and reduction of liability for negligent care.2      success rate of implants according to treatment data
   Risk assessment is a formal procedure used to          compiled from such multicentre trials with
assess the significance of risks in order to facilitate   Brånemark osseointegrated implants (Nobel
the decision making process. Originally, it was           Biocare, Göteborg, Sweden) has been reported for
developed as a tool for the aerospace and nuclear         single tooth restorations,9 partially edentulous
industries but subsequently has been applied              bridgework,10 overdentures11 and fully edentulous
increasingly in many different areas such as the          bridgework.12 The results are based on a minimum
petrochemical industry, drug safety and eventually        followup of five years and are shown in Table 1 along
                                                          with comparative success rates. The outcome
the healthcare field. Risk assessment, in a clinical
                                                          measures of these trials have been subsequently
setting, has for its basis the assumption that a
                                                          employed in everyday practice. Such systematically
procedure may expose the individual to some
                                                          developed, evidence-based guidelines have provided
consequence or harm. It is a relatively new concept
                                                          an important link in the transfer of information to
in dental practice, however the profession must
                                                          the patient as well as playing a role in ensuring the
come to terms with such contemporary issues, not
                                                          quality of care, thus reducing the risk of liability for
only with respect to duty of care but also to meet the
                                                          negligent care. Combined with clinical judgement,
demands of third party agencies and regulatory            this knowledge base has produced clinically valid
bodies.                                                   recommendations for appropriate treatment.
   The traditional legal standard of ‘commonly               Patient decision-making is based on a multitude
accepted practice’ is beginning to be rendered            of considerations, including success rate and
obsolete. The large variations in dentists’ philosophy    concern for risk of complication. The data pertinent
and practice with respect to diagnosis and treatment      to these outcomes is accumulating rapidly and is
planning are well known.3 Furthermore, improvement        readily available to both dentist and patient from
in these fundamental procedures has not occurred in       both professional and commercial sources. Typical
recent years.4,5 The evidence-based practice              clinical outcomes are outlined below.
approach appears to be a natural evolution for the
practitioner.6 The modern concept of evidence-            The single tooth implant
based practice was introduced in medicine by                 A 10-year followup of single tooth implant treat-
Sackett et al7 and defined as ‘. . . the conscientious,   ment is seen in Fig. 1. The biological price of this
explicit and judicious use of current best evidence       treatment was an installation osteotomy site drilled
making decisions about the care of individual             into the jaw bone, together with a 1-2mm marginal
patients. The practice of evidence-based medicine         bone loss over the long term in response to bone
means integrating individual clinical expertise with      remodelling under the functional load. The majority
the best available external clinical evidence from        of such bone loss, when it occurs, is usually seen as
systematic research.’                                     remodelling down to the first or second thread on a
   The increasing emphasis on this important issue        Brånemark System implant.
has resulted in the production of user-friendly              Clinical experience, patient preference and an
guidelines aimed at facilitating the interpretation of    evidence-based approach have combined to form a
the literature for the busy dentist.8 This review will    strong case for the single-tooth implant supported
focus on the contemporary notion that implant             restoration as the undisputed first choice for
treatment is now a realistic option for tooth             uncomplicated restoration of the single missing
replacement in everyday general practice and is in        tooth in many situations.13 Implants can be effective
fact the appropriate treatment in many cases.             in preserving intact teeth in patients undergoing
Australian Dental Journal 2000;45:3.                                                                               151
                                                                                                        Fig. 1. – Tooth 10-year
                                                                                                        fllowup. (a) Left maxillary
                                                                                                        central incisor implant. (b)
                                                                                                        Radiographic remodelling of
                                                                                                        marginal bone down to the
                                                                                                        level of the second thread of the

  a                                                                  b

  a                                                                  b
 Fig. 2. – Reconstruction of the partially edentulous mouth with both freestanding implant bridgework and traditional tooth-supported
 restorations. (a) Pre-operative radiograph showing extensive occlusal collapse and disorientation of plane of occlusion. (b) Five-year
                   postoperative followup showing various lengths of implants as dictated by adjacent anatomical structures.

                                                                     Fig. 3. – Combination implant-tooth bridgework with non-rigid
                                                                     interlock. Note intrusion of the natural tooth segment, one year

initial prosthodontic therapy and in preventing the                    pocket bleeding index and tooth implant mobility
use of additional teeth as abutments in patients                       between year one and year three of a multicentre
whose existing prostheses must be replaced.14 The                      study.16 When the results from fixed partial denture
safety of the Brånemark implant for tissue-integrated                  studies (bridges) were pooled in a meta-analysis, the
replacement of the single tooth has been described.15                  survival rate was 93.6 per cent after six-seven years.
No significant changes have been observed in the                       The corresponding value for single-tooth implants
status of the gingivitis, pocket depth, periodontal                    was 97.5 per cent.17 When these considerations are
152                                                                                                     Australian Dental Journal 2000;45:3.
combined, the conclusion is that the single tooth           procedure must be considered as experimental and
implant is the standard of care for the uncomplicated       not suitable at this point in time for application in
replacement of single missing teeth.                        general practice.
   Many practitioners are also interested in the
immediate placement of implants into extraction             Partially edentulous implant bridgework
sockets. A number of studies have focused on the               The use of oral implants in the treatment of the
potential for early failure rates of Brånemark              partially edentulous jaw has become a well
implants immediately placed into extraction                 established and accepted contemporary clinical
sockets.18-22 However, comparable failure rates have        method.26 There is ample documentation that the
been observed for implants placed using the                 Brånemark System has predictable medium-term
immediate and delayed techniques, 2.3 per cent and          success.27-33 Furthermore, one study reported 10-
2 per cent respectively. It is emphasized that if           year followup data providing excellent survival
periodontal or periapical infection is present, then        rates.34 Good mucosal health and little marginal
implantation should be delayed pending resolution           bone loss were observed and no severe complications
of the infectious process.                                  were reported. These results compare more than
   One prospective multicentre study involving 12           favourably with the success rates of traditional
centres, two of which were in Australia, followed           bridgework on natural tooth abutments. Patients are
different immediate and delayed immediate implant           increasingly adopting the implant option to avoid
placement techniques.23 Over 50 per cent of the             extensive destruction of the residual dentition in the
cases were single-tooth situations. The reason for          rehabilitation of the partially edentulous jaw.
tooth extraction was evaluated; bone quality and               The clinical guideline for posterior bridges in
quantity were classified; socket depths were                terms of support is one implant for each missing
registered; and data on implant type, size and              tooth, with the avoidance of cantilevers where
position were collected. A followup evaluation was          possible. A cantilever should not be placed on two
carried out on 125 patients after one year of loading       implants. When cantilevers are used on three or
and on 107 patients after three years of loading.           more implants, the design must be limited to only
Clinical parameters (bleeding or not bleeding, pocket       one cantilever pontic, anteriorly placed. The clinical
depth, and implant mobility) were evaluated after           guideline for anterior bridges is similar to bridge
one and three years and the marginal bone level after       design on natural teeth. Thus, four missing incisors
one year of loading was measured on the                     can be restored by a four-unit bridge supported by
radiographs. Clinical comparisons were performed            two implants. Examples of fundamental design
to evaluate implant loss in relation to implant type,       concepts are illustrated in Fig. 2. Design criteria are
size, position, bone quality and quantity, socket           related to biting forces and occlusal loading in
depth, reason for tooth extraction and placement            different areas of the occlusal scheme.
method. In addition, life table analysis was under-            Dentists have always been intrigued by the idea of
taken for cumulative implant survival rates. There          connecting teeth to implants. Using a combination
was no clinical difference with respect to socket           of teeth and implants to support bridgework is
depth or when comparing the different placement             unpredictable unless the teeth and implants are
methods. A higher failure rate was found for short          rigidly joined. Concern has focused on the
implants in the posterior region of the maxilla and         phenomenon of natural tooth intrusion in non-rigid
when periodontitis was cited as a reason for tooth          constructions.35-37 The cause of intrusion is still not
extraction. Mean marginal bone resorption from the          clearly understood and the concept should be avoided
time of loading to the one-year followup was 0.8mm          in general practice. An example of such a problem is
in the maxilla and 0.5mm in the mandible. Over a            shown in Fig. 3. One well-controlled study
period of three years, the implant survival rate was        demonstrated similar success rares when three-unit
92.4 per cent in the maxilla and 94.7 per cent in the       bridges were placed on two implant abutments and
mandible.                                                   compared and contrasted with three-unit bridges
   The use of guided tissue regeneration in                 placed contralaterally on one tooth and one implant
conjunction with single tooth implants has had              rigidly joined. After five years, both designs had a
variable success. Great enthusiasm has been                 similar success rate.38 A single implant and a single
expressed by some clinicians; however, in some              tooth as abutments for a three- to four-unit fixed
studies, the use of these barrier membranes has been        partial denture, made in a straightforward manner as
associated with increased infection rates which may         a one-piece restoration and cemented with a
negatively affect implant survival.20,24,25 The notion of   permanent luting agent, have been widely used, with
single-stage surgery and immediate loading has also         few long-term problems reported. It seems the
been the subject of considerable recent debate. No          complications with attaching teeth to implants are
prospective trials are yet available and such a             primarily limited to tooth intrusion problems. If the
Australian Dental Journal 2000;45:3.                                                                           153
Table 2. Pilot study T033C: Single stage surgery           Table 3. Cost calculation formula for mandibular
(mandible) seven-year followup                             implant prostheses*
Number of patients                                    5                                                                      %
Implants immediately loaded                          20
                                                           Component costs                                                  22.5
Sleeping, reserve implants                           10
                                                           Surgical fee                                                     30.0
Total implants                                       30
                                                           Prosthetic fee                                                   30.0
Cumulative success rate of implants                 100%   Laboratory fee                                                   17.5
Cumulative success rate of fixed partial dentures   100%   Total                                                           100.0
                                                           *Based on five implants, hybrid fixed prosthesis.

tooth is prevented from intruding, either with a
permanent cement or with a mechanical locking              instrumentation and component costs. An analysis
device such as a horizontal screw attachment, the          of the overall cost calculated for implant fixed
concern might diminish.39                                  prosthetic treatment is presented in Table 3. The
                                                           problem of instrumentation and component cost
The edentulous mandible                                    must be viewed in the context of the entire cost
   The big breakthrough in predictability with dental      structure. Many professionals demand reduced
implants was the original Brånemark research for           instrumentation and component costs but do not
treatment of the edentulous jaw with fixed implant         consider reducing their professional fee.
retained prosthesis. In many parts of the world, how-      Unfortunately, human nature is such that others see
ever, there was a need and demand for less expensive       the debate for lower instrumentation and component
solutions and, accordingly, the implant-retained           costs as an opportunity for greater profitability. To
overdenture has emerged as a common treatment              substantially reduce the cost of treatment, it is
alternative. This is especially applicable in patients     necessary that all parts of the equation be addressed,
seeking improved denture service rather than               as reducing instrumentation and component cost
replacement of a removable denture with something          does not dramatically affect the total equation.
fixed, for either psychological or functional reasons.        Rationalized treatment planning for fully
   It has been shown that the implant-supported            informed patients has increasingly challenged one of
fixed prosthesis is more successful than the retained      dentistry’s basic principles – that teeth are best
overdenture in terms of marginal bone height loss,         retained and prevention is the best cure. Increasing
individual implant failure rate and type of therapy.40     numbers of well-informed patients are selecting the
Nevertheless, as previously discussed, some patients       implant rehabilitated edentulous state as a
prefer an implant-retained overdenture and many            predictable alternative to a depleted downhill
clinicians consider the overdenture restoration to be      dentition. Such anecdotal observation suggests that
more universally applicable and cost-effective.            many patients are sceptical of complex and expensive
Intermediate-type hybrid designs that use complete         procedures with limited evidence-based planning.
arch implant-anchored substructure with detachable         The decision to retain limited numbers of teeth
suprastructure provide a further option for some           should be made in light of the strategic and
dentists and patients. The most effective attachment       psychologic value of those teeth to the patient, with
system for detachable overdentures remains                 respect to the various treatment alternatives and
unresolved and comparative studies are required.           what might be the treatment of choice for that person.
   The treatment concepts for mandibular fixed             Patients are increasingly aware of accountability and
rehabilitation are well defined with high long-term        increasingly want to know about alternatives, not
success rates replicated in many different centres.40-43   just the dentist’s preference. Today, patients want to
More recently, attention has been given to simplifying     make an informed decision based on treatment type.
treatment and making it more cost-effective. Pilot         They expect unbiased information from the dentist
studies that have used a single-stage surgical             and increasingly want more than one opinion.
approach for both the fixed and removable prosthesis       Accordingly, increasing emphasis is placed on the
concept44,45 have reported success rates similar to        importance of identifying and quantifying the
those experienced with the traditional two-stage           important factors determining the outcome of
surgical procedure. The single-stage surgery and           clinical trials and providing this information to the
simplified prosthetic management advocated for the         patient so that the treatment decision is an informed
fixed prosthesis solution can reduce the real-dollar       one. A number of within-subject studies has
and time-saving costs by up to 25 per cent.44 The          measured how well different types of implant-
same study also demonstrated that four implants            supported prostheses satisfy and improve the quality
predictably provide anchorage for a full arch              of life of edentulous patients.46-48 Such studies using
prosthesis (Table 2). There has been considerable          systematic assessments of fundamental outcome
controversy and criticism of manufacturer                  variables are crucial in formulating future therapeutic
154                                                                                           Australian Dental Journal 2000;45:3.
   a                                                                  b
 Fig. 4. – Brånemark Novum® single-stage surgery with immediate placement of preformed titanium bridgework on the same day.
                      (a) Radiographic appearance at insertion. (b) Clinical appearance, three-month followup.

   a                                                                  b
 Fig 5. – Extended occlusal table on full arch mandibular implant bridgework. (a) Occlusal view, porcelain fused to titanium bridgework.
                        (b) Radiograph illustrating the use of posterior implants eliminating the cantilever design.

   a                                                                  b

 Fig. 6. – Implant rehabilitation with porcelain fused to metal construction in both jaws. (a) Clincal view, aesthetic bridge design.
                                                 (b) Radiographic seven-year followup.

direction across the entire range of decision-making,                  prefabricated components and surgical guides,
from the individual independent patient to                             resulting in the elimination of the prosthetic
community public health policy.                                        impression and attachment of the permanent fixed
  The latest development in treatment of the                           bridge on the day of implant placement. The
edentulous mandible is a protocol and technique                        prefabricated bridge suprastructure is attached to
aimed at minimizing time involved with treatment.                      three implants using a one-stage surgical procedure
The Brånemark Novum concept employs                                    with immediate loading. The success rate of the
Australian Dental Journal 2000;45:3.                                                                                                 155
  a                                                      b

  c                                                      d

                                                        Fig. 7. – Maxillary implant overdenture. (a) Preoperative profile view
                                                        showing necessity for lip support unattainable with fixed restorations.
                                                        (b) Two implants with rigid bar-clip design. (c) Radiographic view,
                                                        preoperative. (d) Radiographic view, postoperative, illustrating
                                                        rehabilitation of the mandibular arch with traditional fixed
                                                        prosthodontics. (e) Clinical view, postoperative.


treatment is 98 per cent.49 An example of this             complete denture. At the author’s centre, one study
development is shown in Fig. 4. The occlusal               focused on implant-retained overdentures in the
extensions of mandibular bridges are provided by           maxilla opposed to cantilevered implant-supported
cantilevers anchored on implants placed anteriorly         fixed bridges in the mandible. Previous patients with
between the mental foramina. This design limits the        a complete maxillary denture opposing a pre-
occlusal extension to the first molar. In cases            existing implant-supported fixed prosthesis in the
requiring more distal occlusal table for either            mandible were solicited for inclusion in the study.
aesthetic or temperomandibular joint support               Less than 7 per cent of the solicited patients were
reasons, implants are placed in the posterior regions      interested in participation because they were happy
(Fig. 5).                                                  with their maxillary complete denture and saw little
                                                           benefit in further implant treatment. However, all
The edentulous maxilla                                     patients were adamant that, if faced with a return to
  Fortunately, the maxillary complete denture is an        a mandibular denture as a result of prosthesis failure,
inherently more satisfactory solution for the              they would seek implant retreatment. It was
edentulous predicament that the mandibular                 concluded that the parameters that influenced
156                                                                                           Australian Dental Journal 2000;45:3.
   a                                    b

   c                                    d

   e                                    f

                                       Fig. 8. – Extensive maxillary bone graft reconstruction. (a) Master cast
                                       showing implant distribution. (b) Provisional fixed bridge, occlusal
                                       view. (c) Patient discontent with phonetic limitation and inadequate
                                       lip-support provided by the fixed restoration. (d) Radiographic view of
                                       bar infrastructure for detachable bridge design. (e) Tissue view,
                                       detachable bridge with precision attachment retention. (f) Palatal view,
                                       designed to contour the palate and meet phonetic requirements.
                                       (g) Clinical view, maxillary detachable restoration demonstrating
                                       patient acceptance.


Australian Dental Journal 2000;45:3.                                                                        157
  a                                                                         b
 Fig. 9. – (a) Clinical indication for Brånemark zygomatic arch implants, showing large maxillary sinuses and poor alveolar bone. (b) 50mm
 long zygomaticus implants providing posterior maxillary anchorage for fixed prosthodontics without bone grafting. Curvilinear zygomatic
 projection reflects tangential positioning of the implants lateral to the frontozygomatic suture and inferior to the palatal aspect of the residual
           alveolar ridge. Single-stage surgery and immediately loaded implants provide support for the fixed mandibular prosthesis.

patient satisfaction were quite different for the                             calculations as to the number of implants required –
maxilla compared with the mandible.                                           is indicative of chaos. An in-depth consensus confer-
   A greater diversity of opinion exists in treatment                         ence dedicated to the maxillary implant-retained
of the maxilla and many fundamental questions                                 overdenture is a high-level priority. Future therapeutic
remain unanswered. Success rates are significantly                            direction cannot be rationalized on the existing base
different than in the mandible and have been related                          of haphazard art form and pseudoscience that
to differences in residual ridge structure, anatomy,                          currently pervades this area of prosthodontics.
bone quality and quantity, biomechanics, phonetics                               The maxillary complete denture situation
and aesthetic requirements. The higher failure rates                          commonly associated with advanced resorption is
in the maxilla are common to both fixed and                                   another problem that requires definitive change in
removable prostheses. Furthermore, some implant                               therapeutic direction because the general morbidity
success rates of the implant-supported and implant-                           and specific failure rates associated with bone
retained overdenture do not meet the advocated                                grafting can be problematic. Certainly, patients who
minimally acceptable criteria for implant success.                            have successful bone grating are most satisfied; how-
The standard maxillary fixed bridge implant design                            ever, failures can be catastrophic and, regrettably,
is based on six implants and provides adequate                                some patients are left worse off as a result of treat-
function with a ‘6 to 6’ occlusal table as shown in                           ment. In many situations, patients who lose implants
Fig. 6. However, the challenge in the maxilla is                              lose multiple implants. The biology of this dilemma
frequently related to high aesthetic demand with                              remains obscure. Furthermore, many potential
respect to facial support as well as dental and gingival                      patients decline the bone graft option. Recently,
visibility factors. In patients with high expectations,                       increased emphasis has been placed on alternative
it may be impossible to meet the requirements with                            anatomic sites for implant placement to obviate the
a fixed bridge if the facial support previously afforded                      necessity for bone grafting. One such example is the
with a denture flange is lost. In such cases an over-                         pterygomaxillary installation site.50,51 This location
denture or detachable bridge must be considered as                            also provides an alternative to sinus lift procedures.
the appropriate treatment. A relatively simple and                            Success rates for this location are encouraging in the
inexpensive treatment option is seen in Fig. 7. A very                        treatment of partial and complete edentulous
complex situation is illustrated in Fig. 8, where a                           conditions by fixed prostheses and compare
fixed bridge following bone grafting failed to meet the                       favourably with the success rates of other anatomic
patient’s aesthetic and phonetic requirements. The                            locations in the maxilla. Another development of
design was subsequently changed to a detachable                               particular interest is the newly developed Brånemark
bridge prosthesis which provided adequate facial                              zygomatic implant. This long implant offers an
support as well as giving acceptable palatal contours to                      exceptionally strong anchorage point for fixed or
fulfil the phonetic requirements. Furthermore, plaque                         removable prostheses and is currently undergoing
control may be facilitated with detachable appliances.                        evaluation in long-term, prospective multicentre
   The plethora of designs seen with implant-                                 clinical trials. An example of this treatment modality
retained overdentures – whether on balls, bars, clips,                        is illustrated in Fig. 9.
milled or spark-eroded suprastructures, with or                                  There is only one 10-year report on the
without palatal coverage and predicted by yardstick                           simplification of treatment in terms of number of
158                                                                                                               Australian Dental Journal 2000;45:3.
implants to reduce the costs and logistic require-         this question, the aims of one study were to
ments. In this study, it was shown that implant-           statistically determine if the suggested hypothesis
supported cantilevered fixed prostheses on four            was valid, that is, whether dependency exists among
implants, in either the maxilla or the mandible, had       implants in the same patient/jaw, and to determine
comparable long-term survival rates for both               how failure lifetable analysis should be calculated. It
individual implants and prostheses when compared           was concluded that both study design and statistical
with patients treated with fixed partial dentures          analysis are of importance when comparing success
supported by six implants.43 It concluded that the         rates from various investigations, since dependency
tendency of some clinicians to place as many               among implants in the same patient or jaw does exist
implants as possible should be seriously questioned.       and may influence the success rates. Consequently,
Future therapeutic endeavours in the maxilla will          it is suggested that only one randomly selected
continue to be significantly dependent on research         implant from each patient should be considered
and development of surgical procedures, application        when calculating such implant success rates.54
of bone induction agents and osteopromotive                   Success rates of treatment cannot be directly
biotechnology.                                             contrasted to the success rates of individual
                                                           implants. Bone quality and quantity in different
Success rates of treatment                                 zones of the jaw cannot be always directly contrasted
   It is important when proposing treatment to             to overall treatment outcome. Moreover, success
inform patients about the long-term outcome. This          rates cannot be extrapolated between systems
information should be based on reports of results          because of the complexity of the variables involved.
found in international peer-reviewed journals.34           Furthermore, because the cumulative success rate is
Shortcomings can easily be found in most previously        highly variable with respect to type of treatment, it
reported investigations. For example, many studies         can be misleading to report on success rates in
may be based on individual clinics or clinicians,          studies involving the utilization of implants for
which limit the value of the analysis, since the studies   different treatment planning purposes. Unfortunately,
are often retrospective rather than prospective,           this is commonly seen in data collected from small
meaning that research parameters and the followup          numbers of cases where an effort has been made to
period have not been decided from the start of the         provide an overall larger number of implants for
study. Prospective studies, however, assess all            statistical purposes. Thus, it is totally misleading to
patients for the same length of time and examine the       quote success rates of a particular type of implant in
same parameters. Multicentre studies have the              a pooled collection of data, as is seen in some
advantage in that they establish uniformity of             studies.55,56 Attempts to compare and contrast this
predictability and provide a greater volume of data        type of data with prospective multicentre data
for more meaningful analysis. Furthermore, because         reported in controlled studies on specific applications
of the large number of investigators involved, they        demonstrate a shortfall in credibility. Comparing
eliminate the possibility of data manipulation and         short-term treatment results with long-term results
artificial enhancement of results. Criteria for success    is also fallacious.
and failure are other important aspects and matters           It is obvious that browsing the literature and
of ongoing debate. Followup parameters should              summarizing conclusions is fraught with
include at least testing of implant mobility and/or        misconception and results in misinformation. The
bone loss using standardized radiographs.52,53 It is       small print must be considered to gain a valid
also important to limit the results to one implant         overview. Other important issues to consider are the
prosthesis design at a time and use well defined           number of patients involved in studies and the
surgical protocols to minimize variables.                  consequences of long-term dropout rates. Dropout
   When evaluating the outcome of oral implant             rates of 18-20 per cent are conservatively encountered
treatment, a statistically important aspect to consider    and, although disappointing, are not unrealistic in
is whether any dependency exists among implants            clinical studies. While lifetable analysis of the
placed within the same patient or jaw.54 In single-        cumulative success rate is a commonly accepted
tooth treatment, loss of the implant means failure of      method of reporting outcome in clinical trials, it can
the treatment concept, whereas in multiple-implant         also be misinterpreted with respect to the
prosthesis, loss of a single implant may not mean the      consideration of dropouts and withdrawals from the
overall treatment fails; for example, in the case where    data. Alternatively, the worst-case analysis offers a
a mandibular implant bridge on six implants                different type of evaluation and prevents the possible
experiences failure of one of the mid-line implants.       artificial enhancement of success rates because the
In such a case, if one implant fails, will the risk of     withdrawals and dropouts are included.This analysis
subsequent failures increase, that is, will any of the     is useful in contemplating the consequences of
remaining implants also fail? In an attempt to study       treatment outcome in populations that are not well
Australian Dental Journal 2000;45:3.                                                                          159
controlled because sooner or later dropouts may          applied and a degree of mobility and peri-implant
surface, probably elsewhere, usually as a result of      bone loss were accepted.59 Subsequently, amended
complication or failure. Conversely, some patients       criteria have been advocated, emphasizing that a
do not return because there are no problems and          satisfactory functioning implant also meets aesthetic
they do not have a reason to return. Thus, the           requirements.60
evaluation is helpful in assessing the reality of the       In long-term clinical studies, the determination of
situation in everyday clinical practice, and further     safety and effectiveness is invariably dependent on
consideration needs to be given to acceptable values     the comparison of safety and effectiveness variables
of worst-case analysis when making recommendations       between treatment and control groups. Actuarial
for acceptance of new clinical procedures.9              lifetable analyses or other comparable survival
   The importance of these issues is that the patient    analyses have therefore been used, because they
really wants to know the worst-case analysis as part     provide the most informative methodology for
of the informed consent process. An example of the       evaluating such data. Accordingly, cumulative
great difference in data presentation is seen in a       success and survival rates emerged as the long-term
closer analysis of single-tooth treatment results by     parameters of functional success. However, concerns
Henry et al.9 In this study, the cumulative success      about the clinical evaluation of osseointegrated
rates were reported as 96.9 per cent in the maxilla      implants resulted in recommendations for the use of
and 100 per cent in the mandible after five years. An    the four-field table, where every implant is evaluated
alternative method of presentation of data is the        as a success, a survival, unaccounted for, or a
four-field diagram showing successful, surviving,
failed and all unaccounted for implants.57 When the
same data in this single-tooth study are subjected to
such a worst-case analysis, the results are 80.7 per                           CLINICAL
cent minimal success rate in the maxilla and 78.9
per cent in the mandible. Therefore, in reality,
clinicians would be better advised to inform patients
that the success rate of treatment is at least 80 per                     INTERCHANGEABLE
cent and not try to sell implant treatment for single-                     MOUNTED CASTS
tooth replacement on the basis of a 99 per cent
success rate. An excellent review on the biological
factors contributing to failures of osseointegrated
implants with in-depth consideration of success                              RADIOLOGICAL
criteria, epidemiology and etiopathogenesis is
available and is highly recommended for all dentists
seeking scientific clarification of the pertinent
issues.26                                                                       SURGICAL
   Long-term prospective trials comparing and                                   TEMPLATE
contrasting the advantages and disadvantages of
various implant systems are in process. However,
this debate continues to be characterized by anecdote,
commodity development and pseudoscience.2 It is
important that dentists accurately document their
recommendations to patients. Today, the numerous
implant systems on the market present with varying
degrees of documentation. A commercial brochure                               IMPRESSION
is not a scientific recommendation upon which                                REGISTRATION
treatment planning should be based.

Long-term aspects of osseointegrated
implants                                                                     FIXTURE LEVEL
  The criteria originally delineating success of
osseointegrated implants emphasized, over time, a
condition of no mobility together with stable bone or
minimal bone loss around individual implants.58                               INTERIM
These criteria effectively separated osseointegrated                     PROSTHESIS AT STG 2
implants conceptually from the previous generation              Fig. 10. – Sequencing protocol for diagnostic
of implants, where less stringent criteria had been                    workup and implant installation.
160                                                                                    Australian Dental Journal 2000;45:3.
failure,57 as outlined above with the worst-case            and do not solve the problem. It is the view of the
analysis example for single-tooth implants. The             courts that the patient must understand the contents
evolution of criteria rating the success of dental          of such documents for them to be valid. This is the
implants reflects the evolution of knowledge of             case irrespective of obtaining the patient’s signature
implant performance and osseointegrated biologic            on such documents. Rather, emphasis should be
reactions. Most criteria are written in the interest of     placed on fully discussing the patient’s concerns in
predictability of performance of an implant system.         easy to understand lay terms documented by clear
While this approach is valuable in the selection of         and concise notes on the clinical record. The clinical
implants for patients, the criteria for bone-level          examination should address all factors applicable to
changes may be unnecessarily stringent for monitoring       general examination procedures for prosthetic or
implant performance in an individual patient. This          prosthodontic treatment, together with additional
need for tempering the application of marginal bone         information relevant to implant placement including
criteria to clinical applications has been illustrated in   residual ridge morphology, dental and gingival
long-term trials.61 Thus far, few data exist on the         aesthetic parameters, smile-line analysis and
long-term aesthetic parameters with respect to              phonetic patterns. Above all, the patient’s expectations
different implant systems. In this context, ‘long-          should be discussed.
term’ implies eight to 10 years and aesthetic
considerations must include soft tissue stability with      Interchangeable mounted casts
respect to abutment crown interface visible zones.             Interchangeable mounted casts are study models
   Long-term biological implications involving              mounted in an articulator and become more
sensitization or malignant transformation are relevant      important as the case becomes more extensive.
over much longer time periods and as yet have not           While single-tooth implant cases may not have the
been studied prospectively. A latency period of 30          necessity for articulator mountings, they are
years was involved in the first reported case of            invaluable, if not mandatory, for fully edentulous
malignant change associated with an orthopaedic             cases and most partially edentulous situations. The
implant.62 A similar latency period was involved in         procedure is essentially a laboratory exercise involving
the first case of malignancy associated with a dental       minimal clinical time.64 In an edentulous case, the
subperiosteal implant.63 Both reports implicated            dentures, together with a face-bow record, are sent
galvanic currents associated with dissimilar metals         to the laboratory, together with an interocclusal
and corrosion. Because osseointegrated dental               registration if a significant slide in centric or occlusal
implants have not yet been reported in any                  discrepancy is present. In the laboratory, the
associations of malignant change and have now been          dentures are directly mounted with fitting surfaces
in use for over 30 years, it is appropriate that patient    blocked out with silicone rubber if undercuts exist,
concerns in this regard be addressed in terms of            so as to subsequently permit removal of the dentures
minimal or no known risk.                                   without fracture of the cast. Laboratory alginate
                                                            impressions are then taken from the occlusal surface
Treatment planning protocol and case                        aspect and these casts are mounted in an inter-
sequencing: Contemporary considerations                     changeable manner. This is accomplished using a
and current recommendations                                 split cast system with magnetic mounting plates
To Stage 1 surgery                                          (Shofu Inc., Kyoto, Japan). The resultant alternative
  A basic protocol is applicable to all the different       mounting of the casts clearly demonstrates the
types of cases and classifications of treatment. A flow     relationship of each residual ridge to occlusal type,
chart depicting the different steps in the treatment        as well as the ridge-to-ridge relationship. If partially
planning process is shown in Fig. 10. The major             edentulous arches are involved then the impressions
considerations in each step are outlined below.             are clinically taken without removable partial dentures
                                                            in situ. These are transferred to the laboratory with
Clinical examination                                        or without an occlusal registration as required. Again,
   The total time for assessment of implant                 this latter protocol involves minimal chairside time.
candidates involves more appointments of greater
duration than for alternative forms of restorative          Radiological stent
treatment. This is because patients have more                  The minimal radiological evaluation for implant
questions and greater time is required for full and         patients is a panoramic radiograph supplemented
frank explanations to provide all necessary                 with periapical radiographs as required, preferably
information so that consent can be as informed as           with a millimetre grid superimposition. A radiological
possible. Efforts to provide all-inclusive, complicated     stent is indicated whenever the thickness of residual
documents referring to every conceivable                    bone and relationship to adjacent anatomical
complication and idiosyncrasy are counterproductive         structures is in doubt. The radiological stent is
Australian Dental Journal 2000;45:3.                                                                              161
       a                                                                     b
      Fig. 11. – (a) Vacuum-formed radiological stent with radiopaque resin material at the proposed implant site.
      (b) Tomogram (Dentascan) view illustrating cross-sectional bony anatomy, proposed tooth position and
                                           intervening soft tissue thickness.

  a                                                          b


                                                            Fig. 12. – Edentulous jaw radiological stent. (a) Duplicated denture
                                                            with tooth cutouts replaced with radiopaque material and retrofitted to
                                                            the interchangeable split cast. (b) Radiological stent in situ with
                                                            occlusion adjusted. (c) Tomogram (Dentascan) showing cross-
                                                            sectional relationship of tooth position to residual ridge. (d) 3D
                                                            reconstruction of jaw bone morphology related to tooth position.


162                                                                                               Australian Dental Journal 2000;45:3.


                                                          Fig. 13. – Clinical sequence for single-tooth implant placement.
                                                          (a) Radiological stent cut back to form a surgical template used to
                                                          dictate implant installation and provide for fixture level registration
                                                          transfer. (b) Template and transfer registration retrofitted to preoperative
                                                          master-cast. (c) Completed implant restoration. (d) Postoperative
   c                                                      radiographic followup of cemented crown.

fabricated specifically for use with 3D computer-            surface of the denture, within the proposed implant
assisted tomography. It is not routinely advocated for       installation area. For a full arch fixed implant bridge,
simple anterior single tooth placements, but is              this might involve every tooth, whereas for an over-
mandatory for installation of implants above the             denture on two implants, it might be limited only to
inferior dental nerve or in more extensive cases             the cuspid teeth. The cutout sections are then
possibly involving bone grafting procedures. In              restored with radiopaque material, either acrylic or
partially edentulous cases, the missing tooth areas          zinc phosphate cement, and subsequently retrofitted
are diagnostically waxed on the cast and the wax-up          back to the interchangeable mounted cast for
duplicated. The duplicate cast is used to vacuum             occlusal adjustment prior to radiological evaluation
form a clear template using a plastic sheet thickness        (Fig. 12). In conjunction with the clinical evaluation,
of 1.5-2mm. Self-curing resin incorporating barium           the radiological assessment will determine whether
sulfate is then placed into the missing tooth areas to       augmentation procedures are needed to re-establish
form a radiopaque stent. This stent is placed in situ        adequate bone mass for implant anchorage and
during the radiological examination of the projected         adequate contour to fulfil the aesthetic expectations
tooth position in cross-section, resulting in                of the visualized treatment objective.
visualization of the bony anatomy and intervening
soft tissue thickness as shown in Fig. 11.                   Surgical template
   In fully edentulous cases, particularly the maxilla,        Following the radiological examination, the radio-
the stent is made by simply duplicating the patient’s        logical stent is converted into a surgical template.
denture in clear acrylic, then removing the                  This involves cutback on the lingual aspect to the
centremost half of each tooth cut down to the fitting        incisal edge of each proposed installation site. The
Australian Dental Journal 2000;45:3.                                                                                               163
  a                                                                      b

  c                                                                      d

 Fig. 14. – Extensive tissue loss following trauma and endodontic failure. (a) Pre-implant situation. (b) Surgical template in situ at implant
 placement, demonstrating extensive bony defects and control of prosthodontically driven implant positioning. (c) Placement of autologous
    onlay bone grafts simultaneous with implant installation. (d) Postoperative followup of three-unit fixed bridge placed on two implants.

labial and/or buccal surface is reduced to within                          Implant installation
3mm of the incisal edge or buccal edge of the                                 The critical issue with utilization of the surgical
occlusal surface. The cutback serves to maximize                           template is in situ location at the time of implant
vision at the time of implant installation, as well as                     installation. This location ensures the implant is
maximizing access for aspiration by the surgical                           optimally placed for restorative purposes.
assistant. Completely edentulous templates are                             Accordingly, it becomes apparent that the cutback
screwed into position using screws inserted into                           procedure is also geared to permit positioning of the
basal bone following flap reflection. The partially                        fixture mount and other installation armamentarium
edentulous template is stabilized by extension on to                       when the template is positioned. Use of the template
at least two teeth on either side of the missing tooth                     only in the early stages of implant osteotomy site
area, or around the entire arch in the case of a free-                     preparation followed by removal prior to implant
end saddle situation. See Fig. 13.                                         installation defeats the object of the exercise and
   The rationale of this protocol is that the same                         results frequently in malposition of the implant.
device is used for both radiological examination and                       Therefore, the accuracy of the template, simplicity
as a surgical guide. This is important with respect to                     of use and ease of removal are of critical concern if
planning restoratively driven implant installation to                      the template is to be used routinely by the surgeon.
ensure that aesthetic expectations are fulfilled. While                    With the team approach to treatment, it is advisable
other designs of surgical guides may be useful, the                        for the restorative dentist to assist at surgery, partic-
described protocol is the most flexible, universally                       ularly in complex cases, so that restorative input is
applicable and user-friendly formula. Moreover, it is                      possible in the event of compromised bone site and
simple in design, easy to fabricate and cost-effective.                    problematic positioning of implants. In cases involving
Unfortunately, it is a fact of life that the majority of                   site augmentation, the decision must be made to
surgical guides fabricated in commercial dental                            carry out grafting as an implant site prerequisite or,
laboratories are not used at the time of surgery and                       alternatively, to carry out the grafting simultaneously
often end up in the refuse bucket.                                         with implant installation. This assessment is based
164                                                                                                           Australian Dental Journal 2000;45:3.
                                                       IMPRESSION REGISTRATION
                                                      AT OR AFTER STAGE 2 SURGERY

                       F/L Imp. Reg               F/L Imp. Reg                       F/L Imp. Reg            A/L Imp. Reg

                                            Fixture Level Attachment            Lab Abutment Selection
               Fixture Level Attachment

                                                 Sub-structure                                 Abutment Level Attachment

                                              SUPRASTRUCTURE                                        SUPRASTRUCTURE

              Fig. 15. – Impression registration protocols, illustrating different pathways dependent on design criteria and
                                                          laboratory sequencing.

on the size of the defect and the experience of the                     plaque control. The pre-existing temporary prosthesis
dental team. The team approach to treatment                             is readapted with soft tissue liner over the healing
implies a surgical-restorative joint level of                           abutments to meet interim functional and aesthetic
responsibility in all aspects of the decision-making                    demands. The healing abutment protocol is
process. A case illustrating these principles is seen in                advisable for general dentists early on in the learning
Fig. 14.                                                                curve of implant prosthodontics because clinical
                                                                        management is less critical and stress levels are
Impression registration                                                 considerably less.
   An impression procedure is carried out at Stage 1
surgery if an interim restoration is planned for                        Between Stage 1 and 2 surgery
insertion at Stage 2 surgery. In some cases, this                          Patients should be reviewed every six-eight weeks
procedure facilitates soft tissue healing and simplifies                with careful attention to interim restorations to
postoperative restorative management. Impression                        ensure mucosal irritation does not occur over
copings and fixture mounts are directly linked to the                   implant sites. Perforation of the mucosa resulting in
surgical template with self-curing or light-cured                       exposure of the implant, augmentation materials or
resin.65,66 The impression record is then transferred                   bone grafts must be treated seriously and referred
to the laboratory and retrofitted to a duplicate of the                 for surgical opinion and management if necessary.
original interchangeably mounted study cast. The                        Bone graft patients require special followup because
split cast system allows a continuous double-check                      exposure will often result in serious compromise and
capability of each stage of the treatment plan as the                   likely loss of implant. Ideally, extensive bone grafts
case progresses. It is critical that interim restorations               should not be covered with removable prosthetic
placed at Stage 2 surgery are screw retained because                    appliances for at least six weeks postoperatively. This
cemented restorations may work loose, resulting in                      issue needs careful preview when planning treatment
serious soft tissue complications if the tissues are                    and in some cases may preclude treatment.
challenged by acute inflammatory insult in the                          Management of bone-grafted patients is best carried
short- to mid-term postoperative healing period.                        out at the specialist level or only by general dentists
Consequently, such interim restorations must be                         with appropriate training and education. In principle,
screw retained using armamentarium capable of                           prosthetic appliances will require alteration and
applying controlled torque so that loosening is                         modification as the healing process progresses and
predictably prevented (Osseocare; Nobel Biocare,                        this requirement makes adequate followup
Göteborg, Sweden).                                                      mandatory.
   Conversely, if healing abutments are to be placed
at Stage 2 surgery, then Stage 1 surgical impressions                   Following Stage 2 surgery
are of no value and are contraindicated. Healing                           Restorative procedures can be finalized any time
abutments permit controlled resolution of the                           after Stage 2 surgery as dictated by soft tissue
surgical wound and allow for ease of access for                         healing and whether or not provisional restorations
Australian Dental Journal 2000;45:3.                                                                                           165
are employed.The first stage in the technical process       attention to followup as do all traditional crown and
of the restoration is the construction of the master        bridge     restorations.   Furthermore,        specific
cast. This is derived from an impression taken at           considerations are applicable to implant systems,
Stage 2 surgery or following resolution of the soft         particularly during hygiene prophylaxis procedures.
tissue healing several weeks later. Impressions may         Biologically, implant restorations are monitored
be at the fixture or implant head level (F/L) or at the     principally in terms of patient satisfaction and
abutment level (A/L).67 This impression procedure           marginal bone levels. Marginal bone height is easily
may follow a number of different formats depending          measured in relation to the thread pattern on screw-
on the complexity of the case and the proposed              shaped implants. In the vast majority of cases, stable
design of the final restoration, as illustrated in Fig.     situations are reached after 12-18 months of
15. Fixture level impressions give the laboratory           function with bony interface remodelling down to
most flexibility in planning and are indicated in any       the first or second thread of the implant. The
cases where the visualized treatment result is not          engineering design of screwed implant systems also
clearly established. Abutment level impressions are         means that the mechanical stability of parts must be
indicated when definitive abutments have been               followed. Protocols for long-term maintenance of
connected. This may be subsequent to or dependent           such restorations have been recommended.71
upon the outcome of a provisional phase or
absolutely determined prior to provisionalization           Identification of high risk categories
especially in cases where aesthetic demand is not              Clinical experiences have identified a number of
critical and can clearly be visualized. The protocols       risk factors associated with higher failure rates.72
are equally applicable for both the single unit and         Poor-quality bone, bone grafts, irradiation, immuno-
multi-unit cases.                                           supressive medications and some disease states are
   A provisional restoration is a blueprint for the final   universally recognized as risk factors. Furthermore,
result, derived after input at laboratory, clinical and     some conditions have been identified as relative
patient levels.68 Provisional restorations take time        contraindications whereby treatment results may be
and cost money and therefore must be built into the         compromised, such as bruxism, alcoholism, tobacco
original treatment plan cost estimate. Provisional          smoking and osteoporosis. Success rates in some
restorations also serve a useful purpose in functional      conditions may be controlled by the application of
remodelling of the implant bone interface as a              altered protocols. These factors are applicable to all
function of time and should be of durable                   implant systems, although some effort has been
construction to last possibly several months or             made to suggest that certain implants may perform
longer.69 This is particularly important if implants        comparatively better under similar circumstances.
are of questionable stability at the Stage 2 surgery.       One such example is that of hydroxylapatite-coated
Cantilever sections on provisional bridge                   implants in poor quality bone. However, the short-
constructions should be minimal or avoided.                 term advantages apparent in animal experiments
Reshaping of soft tissue margins in the aesthetic           have not translated into long-term clinical experiences.
zone can also be considered during the period of            Definitive cause and effect relationships have not
consolidation prior to finalization of the provisional      been reported in multicentre trials and, at present,
as a prerequisite for the permanent construction.           clinical judgement, prudence and full and frank
                                                            informed consent are desirable before treatment is
Long-term maintenance                                       routinely applied in high-risk patients.2
  Once a patient is treated, the osseointegration              The three categories of bruxism, smoking and
team in effect has undertaken a lifelong responsibility     osteoporosis require more detailed consideration
for the maintenance of the bone-anchored                    because they are relatively common in patients seek-
prosthesis.70 Patients require education in their           ing advice and guidance from general practitioners.
responsibilities for home care and the limits of            Bruxism and parafunction were defined as
implant restorations in terms of use and misuse.            contraindications early in the advent of osseo-
Such education is part of the informed consent              integration.73 In the edentulous jaw, bruxism has
responsibility of the dentist. The requirement for          been implicated in higher failure rates and increased
impeccable fit of the prosthetic suprastructure to          incidence of screw loosening together with prosthetic
best distribute forces and functional loading to the        fractures74 and increased loss of bone associated with
anchorage system while minimizing stress to the             poor plaque control.75 There is general consensus
individual mechanical screw components cannot be            that excessive loading or undue stress may induce
overemphasized. Care taken in the immediate post-           bone loss and that secondary bone quality and
insertion period can do much to set the stage for           quantity factors may contribute to this outcome.72
minimizing long-term biomechanical problems.                Bruxism should be managed in implant candidates
Implant restorations require at least the same              in the same manner as for general restorative
166                                                                                     Australian Dental Journal 2000;45:3.
patients, with careful attention being paid to design    caution.89 Commonly, this follows orthodontic treat-
of the occlusal scheme and the nocturnal utilization     ment when one or more implants are placed in the
of an occlusal splint as required.                       aesthetic zone as an alternative to traditional
   Smoking is increasingly incriminated in a number      prosthodontic methods which are seen by parents to
of health issues and is often discussed in relation to   be radical in terms of loss of adjacent tooth struc-
implants. Several studies have shown that smoking        ture. The contemporary demand is for a minimal
can be associated with higher failure rates,             intervention philosophy with decreased invasiveness.
complications and altered soft tissue conditions.76-82   Less common are the more extensive oligodontia
In general, smokers showed approximately twice the       cases where extensive numbers of teeth are replaced
number of failures compared with non-smokers.            in long-term treatment plans involving expanded
While protocols have recommended a period of non-        multidisciplinary teams of orthodontists, surgical
smoking that covers the treatment phase,83 it has also   and restorative practitioners and sometimes
been suggested that patients should stop smoking         orthognathic and craniofacial surgeons. These cases
because of the higher incidence of maxillary peri-       are the province of experienced specialist teams,
implantitis in smokers.84 Further studies are needed     frequently located at children’s hospitals; however,
to determine whether the adverse effects of smoking      the replacement of small numbers of teeth following
on peri-implant tissues are reversible if the patient    orthodontics can be considered as a general
stops smoking, as has been shown in the reduction        dentistry area of responsibility. Nevertheless, careful
of periodontal disease in former smokers compared        treatment planning is required to optimize the final
with active smokers.85 As a future therapeutic           treatment result – in terms of tooth spacing and axial
endeavour, dentists should take a lead role in           inclination to optimize implant installation and
attempting to permanently alter the behavioural          minimize the chances of damage to adjacent teeth
characteristics of patients at risk in this area.        structures. As implants should be placed after the
Training programs aimed at this specific issue have      complete development of the jaw, a critical issue is
existed in medicine for years and it is desirable that   that of timing of implant placement with respect to
dental professionals take a more profound interest in    age. If implants are placed prematurely in the
this educational opportunity.86                          aesthetic zone, continued vertical development can
   Many female patients are concerned that               result in disastrous aesthetic consequences because,
osteoporosis will preclude them from considering         over time, the implants will be ‘left behind’ as a
dental implant treatment because of a lack of bone       result of the biological absence of a periodontal
density and perceived loss of confidence with respect    ligament at the bone implant interface.90
to risk. Although osteoporosis has been considered a     Consequently, in the long term, such restorations
risk factor, particularly for postmenopausal women,      become excessively long and the only effective
no clinical studies have been published. A review of     remedial action is to remove the implant. Such a
the literature suggests there is no scientific back-     procedure is hazardous to adjacent structures and
ground to confirm osteoporosis as a risk factor for      highly problematic in terms of dentist-patient-parent
oral implants.87 Currently, such patients are advised    relationships and is justifiably litigious. The
that treatment is indeed possible for them, however      determination of growth cessation should include an
prolonged healing periods together with careful          orthodontic evaluation of general height and physical
conservative prosthetic management are desirable. A      development as well as radiological evaluation of bone
similar recommendation can be applied to diabetes        development by wrist film.91 It must be emphasized
in light of the recent consensus that placement of       that chronological age in itself is not a sole criterion
implants in patients with metabolically controlled       in the determination of growth cessation process.
diabetes mellitus does not result in a greater risk of   Dentists need to be well disciplined in this context,
failures than in the general population.88               especially when confronted by persuasive parents
   In conclusion, if a general dentist is concerned      keen to see the completion of treatment often during
with any aspect of systemic health as it pertains to     times of increased pressure caused by the emerging
oral implants, then opinion should be sought from        social needs and demands of their offspring.
the patient’s general medical practitioner together      Furthermore, careful attention needs to be given to
with referral to dental colleagues with long-term        the requirements of adequate post-orthodontic
experience in the field.                                 retention in the interval between orthodontics and
                                                         placement of implants. In some cases this may be
Implants in children                                     between three and four years and the situation
  Implants are an increasingly popular method of         accordingly requires control and maintenance to
tooth replacement in children with congenitally          prevent orthodontic relapse.
missing teeth; however, the use of osseointegrated          In summary, the successful placement and
implants in growing jaws must be treated with            restoration of single-tooth implants in young
Australian Dental Journal 2000;45:3.                                                                         167
        IMPLANT                              SURGICAL
       HARDWARE                             PROTOCOLS


                                                                        Fig. 17. – Posterior maxillary implants installed to engage residual
                                                                        bony anatomy adjacent to the maxillary sinuses, thus avoiding sinus
                                                                                        lift procedures. Five-year followup.

Fig. 16. – Factors involved in the expansion of treatment procedures.
                                                                        moral and ethical responsibility for better control of
                                                                        this area, and regulatory bodies need to constantly
orthodontic patients requires that a number of                          review and enforce the guidelines.1
interdisciplinary steps be followed. The critical                          Implant installation site improvement has seen a
issues involved have been addressed and a protocol                      rapid development in osteopromotive and site-
suggested to achieve optimal results in a recent                        augmentation technology. This technology has
publication,92 together with a more comprehensive                       resulted in a proliferation of alloplastic products,
treatise of the subject in a recent textbook.93                         independently and in conjunction with autologous
                                                                        tissues, to promote three-dimensional alteration of
Expanding areas of application                                          the recipient site for prosthetically and aesthetically
   Expanded clinical experience is dependent on                         driven restorations. Simultaneously, the develop-
training and education of the workforce to use the                      ment of surgical protocols has enabled many more
existing possibilities, together with a widening of the                 patients to receive treatment that was not possible a
indication base as a result of improved technology                      decade ago. On the one hand, procedures providing
and surgical development. The factors involved in                       greater access to greater bone volume for possible
the development of implant treatment are shown in                       implant placement, such as inferior dental nerve
Fig. 16. Implant hardware development is a                              lateralization and sinus lift procedures, have
continuum to meet the demands of existing clinical                      expanded treatment options. One such example is
situations where shortfalls are obvious.This has seen                   the conservative bone-added osteotome sinus floor
the introduction of various-sized implants to suit the                  elevation technique,94 a major advance over the
different conditions of jawbone anatomy so that                         classical sinus lift procedure which is subject to
hardware selection can be customized to meet the                        greater morbidity and conflicting results on safety
specific requirements of the recipient site. Similarly,                 and efficacy. On the other hand, procedures utilizing
prosthodontic requirements have dictated consider-                      existing anatomical situations, offering reduced
able development in abutment design in recent                           morbidity and minimal interference and invasion of
years. Surface design and surface treatment are                         existing anatomical structures, have emerged. Figure
other areas continuously under development, with                        17 illustrates the case of a 36 year old female who
many innovations being based on perceived market-                       declined sinus lift procedures. Alternatively, pterygo-
place commodity opportunity rather than on                              maxillary implants were placed to engage the
scientifically based research and development. Such                     residual bony anatomy and provide posterior
manufacturing policy is opportunistic as the market-                    anchorage points. Elsewhere in the jaw, the principle
place expands into general dentistry and away from                      of implant installation engaging minimal residual
the specialist areas. The need for documentation at                     bone is shown.
the generalist level is less demanding and                                 In the last five years, there has been rapid
promotional literature can, of necessity and                            development of orthodontic applications of dental
desirability, be more simplistic and misleading.                        implants to provide anchorage for orthodontic,
Manufacturers and industry should accept the                            orthopaedic and orthognathic movements.
168                                                                                                        Australian Dental Journal 2000;45:3.
Miniature implants and onplants are also finding          in achieving high success rates in Sweden and
increasingly wider application in oral and maxillo-       internationally. While this concept of specialized
facial surgery in conjunction with osseodistraction       manpower is applicable in some areas of the world,
and orthognathic surgical fixation and stabilization,     it is not universally so. Consequently, some rational-
resulting in decreased relapse rates. Congenital          ization of the problems to be faced by organized
anomalies and developmental defects of the face and       dentistry is a necessity. Accordingly, the clinician
jaws often present orthodontic anchorage challenges       may well be faced with the dilemma of how best to
in which the residual dentition cannot be adequately      implement changes in terms of efficiency and cost
positioned for restorative objectives. A recent           benefit to the patient. While the structure of
classification of the formulation of implant-based        organized dentistry might be conceptually different
treatment protocols in children reviewed the              in different parts of the world, the types of dentists
application of implants in the developing dentition       who show interest in implant dentistry have much in
and provided guidelines for occlusal treatment.           common the world over.
Procedures performed according to the protocols              Oral surgeons exist as true specialists in most
outlined in this article can facilitate orthodontic and   parts of the world. Those surgeons engaged
orthopaedic movement and accelerate three-                principally with maxillofacial reconstruction and
dimensional jaw movement by sutural distraction of        extensive orthognathic surgery may not be attracted
basal bone.95                                             to the perceived mundane aspects of dento-alveolar
   Increased utilization in the surgical and prosthetic   surgery involving the placement of titanium
craniofacial rehabilitation of congenital, traumatic      implants in the jawbone. Nevertheless, the majority
and surgical defects has further enhanced the overall     of oral surgeons have accepted the concept of
clinical experience of dental implants. The loss of       osseointegration as a most significant advance.
facial parts as a result of either accident trauma or     Conversely, there are many general dentists who
cancer therapy often leaves the individual psycho-        consider themselves to be quite capable of inserting
logically shattered and unable to lead a normal life      implants. Most certainly, the placement of implants
because of dehabilitated appearance. Patients             into bone-grafted sites and the special considerations
treated with osseointegrated implant-anchored             and ramifications of anatomical structures such as
maxillofacial prosthesis often enjoy an improved          the inferior dental nerve, the maxillary sinus and
quality of life at a level unattainable with the          floor of the nose fall clearly into the realm of the oral
previous generation of adhesive anchored prostheses.      surgeon. The view must be expressed that, in the
Followup results in excess of 10 years have               above situations, dentists other than oral surgeons
demonstrated the replicability of this form of treat-     put patients at greater risk when placing implants.
ment in Australia and have yielded results that           The prosthodontist sees the treatment of the
compare favourably with those reported elsewhere.96       completely edentulous jaw by osseointegrated
Many of these treatment endeavours are still largely      implant-supported bridgework as true rehabilitation
at the pilot study level of development and long-         to a near-normal state. Bone anchorage can also be
term prospective clinical trials on large numbers of      used to support a variety of prosthodontic modalities
patients are required to document results adequately      for many difficult developmental defects, such as
and to elucidate the most likely productive areas for     cleft palate. Oral surgeons will probably provide
future investigation and controlled development.2         treatment for more complex cases while periodontists
                                                          have become increasingly involved in the treatment
Philosophical dilemmas in the clinical                    of the partially edentulous mouth. Concomitantly,
practice of implant dentistry                             the general dentist with expertise in minor oral
   As with any change in the clinical practice of         surgery will find the overall economics of in-house
medicine and dentistry, controversy, scepticism and       treatment increasingly attractive, rather than
resistance are necessary prerequisites to the             employing the specialist referral policy. This is most
advancement being fully endorsed by the profession.       likely to be true in the single-tooth application where
In the last five years, osseointegration has caused an    possibly the final ideal aesthetic result is best
explosion of interest in implant dentistry, both by       controlled by a single operator.
specialists and general practitioners. The clinician         In one study, a group of dentists in general and
who has made the decision to incorporate implants         restorative dental practice, with no previous
into an existing practice philosophy must seriously       experience in implant surgery, underwent intensive
consider the basic philosophical tenets upon which        training in all aspects of implant treatment for single
treatment is based. Historically, in Sweden, the          teeth. Using a system of simplified instrumentation
treatment system was developed as a team concept          with a strict adherence to protocol, the group
of surgeons working in close cooperation with             installed and restored single-tooth implants ad
prosthodontists. This team concept was instrumental       modum Brånemark in a wide range of clinical
Australian Dental Journal 2000;45:3.                                                                           169
applications. At followups after crown insertion, the     dentists have a responsibility to discuss the implant
success rates compared favourably with results            option with patients considering tooth replacement
reported from other centres using the specialist-         alternatives. The level of involvement of general
team approach to treatment.The results of this study      dentists in implant treatment is a function of
indicate that further consideration should be given       education and training with a minimal requirement
to the training of general dentists so that improved      being the motivation to refer the patient to the
delivery of dental health care can be provided at a       appropriate colleague. The maximum level of
more economical level.97 While this study was             involvement is dependent on the degree of expertise
limited to the single-tooth indication for treatment,     and experience developed from involvement in
there is no reason why trained general dentists           postgraduate and/or formal continuing education
cannot perform more advanced procedures as                programs. Treatment methods should be evidence-
dictated by the levels of training and education to       based and patients need to be advised that implant
which they aspire. The general dentist is likely to       restorations are subject to followup and maintenance
have the greatest difficulty incorporating osseo-         and do not differ in this respect to other types of
integration into a successful practice, particularly if   extensive prosthodontic treatment. Clinical
the practice is very busy. The change in treatment        experience, patient preference and an evidence-
planning philosophy of this restorative aspect of         based approach have combined to form a strong case
general practice will demand considerable time and        for the single-tooth implant restoration as the
effort in reorganization of the practice to adopt the     undisputed first choice in the uncomplicated
new modality. The entrepreneurial dentist will have       replacement of the single missing tooth in many
little difficulty; however, the conservative counter-     situations.
part will probably have great difficulty in terms of
the cost-benefit analysis and time involved.              Acknowledgements
Nevertheless, dentists will find it necessary to            The oral and maxillofacial surgical aspects of the
confront this dilemma if they are to offer their          cases presented in this paper were carried out by Dr
patients the best treatment solutions available. The      EA Adler, Dr BP Allan, Dr I Rosenberg and Dr RA
time is imminent where such action will be strongly       Williamson. The author* recognizes their expertise
advised if they are to fulfil the requirements for        and commitment to the team approach to treatment
proper informed consent, in light of modern dental        in meeting prosthodontic needs and demands and
care ramifications of osseointegration.                   fulfilling patient expectations.
   However, despite the capabilities of an individual     *The author’s involvement in the multicentre clinical trials was funded,
clinician, many patients prefer a team approach to        in part, by project grants from Nobel Biocare, Goteborg, Sweden.

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