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Root end filling materials — A review

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					                                                                                Endodontology, Vol. 15, 2003



Root end filling materials — A review
Vasudev SK* Goel BR** Tyagi S***


                                               ABSTRACT

        The main objective of all endodontic procedures is to obtain a hermetic
        seal between the periodontium and root canal foramina. When this is not
        possible by an orthograde approach, root end filling technique is used.
        Numerous materials have been suggested for root-end filling. This article
        reviews on the suitability of various root end filling materials from past to
        present.

        Key Words: Root-end filling materials, hermetic seal, biocompatibility,
        microleakage.
Introduction                                               by-products into the periradicular tissues. It
                                                           should also be non-toxic, non-carcinogenic,
     Most endodontic failures occur as a result            and biocompatible with the tissue fluids and
of leakage of irritants from pathologically                dimensionally stable. The presence of
involved root canals. When non-surgical                    moisture should not affect its sealing ability.
attempts prove unsuccessful or are                         For practical purposes, it should be easy to
contraindicated, surgical endodontic therapy               use and be radio-opaque, to be recognized
is needed to save the tooth. The root-end filling          on the radiograph.
material should provide an apical seal to an
otherwise unobturated root canal or improve                    Throughout the dental history, a wide
the seal of existing root canal filling material           variety of materials have been used for
and be biocompatible with the periradicular                retrograde fillings. Although a plethora of
tissues.                                                   materials are available, no material has been
                                                           found that fulfills all or most of the properties
    The complexity of root canal systems,                  for ideal retrograde filling material. Given
inadequate instrumentation and presence of                 below is the list of materials that have been or
physical barriers may necessitate surgical                 are currently being used as retrograde filling
endodontic therapy in some cases. Once the                 material.
root-end preparation has been completed, a
suitable root-end filling material is inserted.                 Metals such as gold-foil, silver posts,
According to Gartner and Dorn 1 an ideal                   titanium screws, tin posts , amalgam (with and
material to seal the root-end cavities should              without bonding agent) and gallium alloy are
prevent leakage of microorganisms and their                some of the solid, commonly used retro-filling
                                                           materials.
* Post Graduate Student
** Professor and Head,                                         Cements and sealers such as ZnOE
    Deptt. of Conservative Dentistry & Endodontics,
                                                           Cement IRM, Super EBA, cavit, zinc-
    P.M.N.M. Dental College and Hospital,
    Bagalkot – 587 101.                                    polycarboxylate, zinc phosphate and glass
*** Assistant Professor                                    Ionomer cements, mineral trioxide aggregate,
    Deptt. of Conservative Dentistry & Endodontics,        calcium phosphate cement and bone cement
    Oxford Dental College
                                                           have also been employed for retro-fillings.
    Bangalore
                                                      12
Vasudev SK et al.                                                                    Root end filling materials.

   Other commonly used materials are                         was not advocated. Orthograde gutta-percha
composite resin (with and without bonding                    root canal obturation that is associated with
agent) and gutta-percha.                                     apical surgery is burnished after apicoectomy
                                                             with either cold or hot burnisher. Its adaptation
    The less commonly used materials are
                                                             to root dentin walls can also be accomplished
laser, citric acid demineralization, ceramic
                                                             with the use of solvents, excavators, scalpels
inlay , teflon, mixture of powdered dentin &
                                                             and burs. Abdal and Retief in their study
sulfathiazole and cynoacrylates
                                                             observed that heat sealed gutta-percha
    Based on review of literature on scientific              provides a better seal as compared to
evaluation and clinical usage, the following are             Amalgam, IRM and Super EBA4. It is reported
the commonly used root end filling materials.                that a better seal can be obtained with thermo-
                                                             plasticized gutta-percha than amalgam with
Amalgam                                                      and without varnish5-7.
      It is the most extensively used retro-filling              Due to it’s porous nature, it absorbs
material from past seven decades, but one of                 moisture from surrounding periapical tissue
the first reports of placing it as a root-end filling        and expands initially, which is followed by
subsequent to resection is attributed to Farrar              contraction at a later stage. This may result in
(1884). Later Rhein (1897), Faulhaber &                      poor marginal adaptation and increased micro
Neumann (1912), Hippels (1914) and Garvin                    leakage.
(1919) extolled the use of root-end amalgam
fillings. Amalgam is easy to manipulate and                  Zinc Oxide Eugenol (ZOE) and
has good radio opacity. It is non-soluble in                 Reinforced ZOE Cements
tissue fluids and marginal adaptation as well                     The use of ZOE as a root-end sealing
as sealing improves as amalgam ages due to                   agent in periradicular surgery has had limited
formation of corrosion products. High copper                 documentation. Newer modifications of ZOE
zinc free amalgam is preferred. Use of                       compounds, such as IRM and Super EBA
Amalgambond, a 4-META bonding agent with                     provide a better apical seal. IRM is zinc oxide-
amalgam significantly reduces the                            eugenol cement reinforced by addition of 20%
microleakage of amalgam retrofillings 2 .                    polymethacylate by weight to the powder8.
Compatibility studies have demonstrated that                 Studies reveal that IRM seals better than non
freshly mixed conventional silver amalgams                   zinc amalgam 9. Super EBA is zinc oxide-
are very cytotoxic due to unreacted mercury3,                eugenol cement modified with ethoxybenzoic
with cytotoxicity decreasing rapidly as the                  acid to alter the setting time and increase the
material hardens.                                            strength of the mixture8. Super EBA has much
     Amalgam has few limitations which                       better physical properties than ZOE. It showed
include initial marginal leakage, corrosion, tin             high compressive strength, high tensile
and mercury contamination of periapical                      strength, neutral pH, and low solubility. Even
tissues, moisture sensitivity of some alloys,                in moist conditions Super EBA adheres to
need for retentive undercut preparation,                     tooth structure. Super EBA adheres well to
staining of hard and soft tissues and technique              itself and can be added incrementally as
sensitivity1.                                                necessary but IRM does not. Reports showed
                                                             a good healing response to super EBA with
Gutta Percha                                                 minimal chronic inflammation at the root
    Until      the      development        of                apex 10 . EBA demonstrates virtually no
thermoplasticized gutta-percha, the placement                leakage11-12. Super EBA and IRM showed less
of gutta percha as a root-end filling material               leakage as compared to silver amalgam13.
                                                        13
                                                                                Endodontology, Vol. 15, 2003

   Super EBA provides a better seal, when                of polyacrylic acid which, when mixed and
compared with amalgam as a root-end filling              hardened, forms a cement of zinc oxide
material14-15. Based on the above studies, the           particles dispersed in a cross linked
use of EBA as a root-end filling material is             structureless matrix of zinc polycarboxylate.
promising.                                               The pH of the cement is approximately 1.7,
                                                         which rapidly increases as the cement sets.
Cavit
                                                         Despite their initial acidic nature, minimal
      It is a Zinc oxide based temporary filling         irritation has been reported to the dental pulp
material. Cavit is soft when placed in the tooth         when placed on adjacent dentin22 or used as
and subsequently undergoes a hygroscopic                 a direct pulp cap23. Polycarboxylates placed
set after permeation with water, giving a high           in root canal systems or beyond the confines
linear expansion (18%). This rationalizes its            of root apex show a varied periradicular tissue
use as a root-end filling material. Cavit has            response. Apical leakage studies have
been shown to exhibit greater leakage than               indicated that polycarboxylates, when used as
IRM16. It is found to be soluble and quickly             root-end fillings, leak at levels significantly
disintegrates in tissue fluids. Biocompatibility         greater than amalgam or gutta-percha.
studies with Cavit are in conflict, showing it to
                                                             Based on their poor sealing ability and
be both toxic17 and nontoxic18. Keeping these
                                                         uncertain periradicular tissue response, the
studies in mind, the use of Cavit as a root-end
                                                         use of polycarboxylate as root-end filling
filling material cannot be advised.
                                                         material is highly questionable. Further
Gold Foil                                                evaluation may be warranted.
     First reports of its use as a root-end              Zinc phosphate cement
material is attributed to Schuster in 1913 and
                                                               Rhein in 1897 used zinc phosphate
Lyons in 1920. It exhibits perfect marginal
                                                         cement along with gutta-percha to seal the root
adaptability, surface smoothness and tissue
                                                         canal system prior to root-end resection. In
biocompatibility. Implants of gold foil produce
                                                         1941 Herbert recommended zinc phosphate
only mild tissue reaction19. When compared
                                                         mixed with powdered thymol as a root-end
to IRM, composite resin, amalgam and glass
                                                         filling material following root-end resection. As
ionomer, goldfoil was least toxic20. Gold Foil
                                                         previously discussed, the root-end filling
was found to be the best apical sealing
                                                         material should be nonirritating, not inhibit
material as far as the improvement in biting
                                                         healing, and exhibit minimal, if any, leakage
force is concerned21. Leakage studies in root-
                                                         or solubility. Since zinc phosphate does not
end preparations have indicated minimal or
                                                         fulfill these criteria, it is not indicated as a root-
no leakage. The routine use of gold foil as a
                                                         end filling material.
root-end filling material does not appear
practical because of the need to establish a             Glass Ionomer Cement (GIC)
moisture free environment, careful placement
                                                              Glass ionomers are formed by the reaction
and finishing. However its use in isolated
                                                         of calcium–aluminosilicate glass particles with
cases can be justified.
                                                         aqueous solutions of polyacrylic acid. It bonds
Polycarboxylate cement                                   physico-chemically to dentine. Biocompatibility
                                                         studies have shown evidence of initial
    It was introduced by Smith in 1968. The
                                                         cytotoxicity with freshly prepared samples, with
zinc polycarboxylate cement consists of a
                                                         decreasing toxicity as setting occurs. It is easy
powder having modified zinc oxide with fillers
                                                         to handle and does not cause any adverse
and a liquid comprising of aqueous solution
                                                         histological reaction in the periapical tissue24,25.
                                                    14
Vasudev SK et al.                                                                Root end filling materials.

Sealing ability of GIC was adversely affected               The proper use of dentin bonding agents
when the root end cavities were contaminated            and composite resin may play a significant role
with moisture at the time of placement of               in enhancing the final root-end filling and the
cement26. Marginal adaptation and adhesion              benefits of their use warrant further evaluation.
of glass ionomer cements to dentin have been
                                                        Mineral Trioxide Aggregate (MTA)
shown to improve with the use of acid
conditioners and varnishes27. Light cure, resin               It was developed at Loma Linda University,
reinforced GIC was used as a retrograde filling         CA, U.S.A in 1993. This cement contains
material by Chong et al28. It showed least              tricalcium silicate, tricalcium aluminate,
microleakage due to less moisture sensitivity,          tricalcium oxide, silicate oxide and other
less curing shrinkage and deeper penetration            mineral oxides forming a hydrophilic powder
of polymer into dentin surface.                         which sets in presence of water. The resultant
                                                        colloidal gel solidifies to a hard structure within
    Newer glass ionomer cements containing
                                                        4 hours. Initially the pH is 10.2 which rises to
glass-metal powder have been reported to
                                                        12.5 three hours after mixing. It is found to be
have less leakage29 and showed no pathologic
                                                        more opaque than EBA and IRM. MTA
signs. Their use as root-end filling materials
                                                        provides superior seal when compared with
is promising and further evaluations are
                                                        Amalgam, IRM and Super EBA34. Adamo et
warranted.
                                                        al35 compared MTA, Super-EBA, Composite
Composite resin                                         and amalgam and found statistically no
                                                        significant difference in the rate of
      Composite resins due to their cytotoxic or
                                                        microleakage but studies of Torabinejad et al
irritating effects on pulp tissue have received
                                                        and Fischer et al proved MTA to be superior
minimal attention as root-end filling materials.
                                                        as compared to Super EBA and IRM36. The
The cytotoxic effects are a function of the
                                                        marginal adaptation of MTA was better with
evaluative methods employed, and, when the
                                                        or without finishing when compared to IRM and
agents are properly used, the cytotoxic effects
                                                        Super EBA37. MTA, when used as a root-end
were substantially decreased or eliminated30.
                                                        filling material, showed evidence of healing of
McDonald and Dumsha compared composite
                                                        the surrounding tissues 38-40 . Most
with a dentin bonding agent, composite alone,
                                                        characteristic tissue reaction of MTA was the
cavit, amalgam, hot burnished gutta percha,
                                                        presence of connective tissue after the first
and cold burnished gutta percha and found
                                                        postoperative week41. Studies have shown that
that composite with dentin bonding agent
                                                        osteoblasts have favorable response to MTA
showed least amount of leakage followed by
                                                        as compared to IRM and amalgam. With
composite alone when both of these were
                                                        longer duration, new cementum was found on
placed directly on resected root surface31.
                                                        the surface of the material42. In a two year
These findings suggest that the preparation
                                                        follow-up study with MTA as root-end filling
of a root-end cavity may be obviated.
                                                        material resulted in a high success rate43. Such
     Light cure composite resin showed                  studies support further development of MTA
significantly lower apical leakage than                 to reduce the long setting time and difficulty in
amalgam and ketac-silver 32. Rud et al 33               manipulation for use as a root-end filling
applied Gluma in vivo to cases requiring                material.
periradicular surgery and compared it to cases
                                                        Calcium Phosphate Cement (CPC)
treated with root-end amalgam fills. Gluma
exhibited complete healing in 74% of the cases             Developed by ADA-Paffenbarger Dental
as compared to amalgam which showed in                  Research Center at the United States National
only in 59% of cases.
                                                   15
                                                                                 Endodontology, Vol. 15, 2003

Institute of Standards & Technology, CPC is             been the Er:YAG at 2.94 micrometers. Komori
mixture of two calcium phosphate compounds,             et al.48 compared CO2, Nd:YAG, Er:YAG and
one acidic and the other basic44. Commonly              Ho:YAG and found that Er:YAG was superior,
known as hydroxyapatite cement, it is                   it showed root surfaces devoid of charring.
composed of tetracalcium phosphate and                  Clinically it’s use improved healing and
dicalcium phosphate reactants. These                    diminished post operative discomfort47. There
compounds, when mixed with water, react                 have been no reports on clinical use of this
isothermally to form a solid implant composed           laser for apicectomy49.
of carbonated hydroxyapatite45. The final set
                                                            The use of laser for apicectomy procedure
cement consists of nearly all crystalline
                                                        has some merits, but it takes more time to
material, and porosity is in direct ratio to the
                                                        perform when compared to more conventional
amount of solvent used. It is as radio opaque
                                                        methods.
as bone. When combined by dissolution in
moisture, even blood, CPC sets into                          Rest of the materials enlisted in this article
hydroxyapatite46. It demonstrates excellent             has received brief mention in the dental
biocompatibility, does not cause a sustained            literature for use as root-end filling materials
inflammatory response or toxic reaction. Its            following periradicular surgery. Little
compressive strength is greater than 60 MPa             substantiation exists for the use of some of
and has shown to maintain its shape and                 these materials, while others require further
volume over time. An in vivo monkey study               evaluation to determine the long term efficacy
found new bone formation developing                     of their use.
immediately adjacent to CPC44. CPC implants
are resorbed slowly and are replaced by                 Conclusion
natural bone in an approximate 1:1 ratio in an                The endodontic surgeon should consider
osteoconductive manner. CPC seems to be                 using materials, which have been biologically
quite promising as a retrograde filling material        and clinically evaluated and which give
but it is yet to get approval from the United           evidence of long term success. The root-end
States Food and Drug Administration.                    filling materials should provide a hermetic seal,
Laser                                                   should be non-toxic, non-carcinogenic,
                                                        biocompatible and dimensionally stable.
    Laser applications for dental practice has          Based on review of literature, it appears to date
been a research interest for the past 25 years.         that the existing root-end filling materials do
First laser, the Ruby laser was developed by            not possess ideal characteristics, but studies
Miaman in 1960. Application of laser in                 have revealed that MTA and Super EBA are
endodontics was introduced by Weilcham in               superior to other retro-grade filling materials.
1971. Studies show that the effects of laser
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Vasudev SK et al.                                                                                 Root end filling materials.

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                                                                                           Endodontology, Vol. 15, 2003

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