INTRODUCTION Biologicalaim for root canal therapy is prevention or elimination of apicalperiodontitis. Elimination of apical periodontitis can be achieved by chemo-mechanicaldebridement of canal walls followed by final obturation. Ideal role for rootcanal filling material should be to disinfect and seal canal in apical, lateral and coronal direction.In ideal condition root filling material should be dimensionallystable, so easily insered into root canals, biocompatible, radiopaque,sterile, bactericidal , easy removal from canal and must not stain tooth structure. Fillingmaterial for root canal should provide strength to remaining root structureas well.
(1)Atpresent, gutta percha along with sealer is considered as the best remedy forroot canal filling. Sealers are capable of filling the voids between gutta-perchacones and the gaps between gutta-percha and dentinal canal walls . Sealing of lateral and apical gaps in root canal system and well adaptation to dentinal canal walls are favourable condition of ideal sealers. In cases like, thinning and weakening of rootcanal walls can occur because of excessive pressure during cleaning andshaping, over -instrumentation, removalof intra-canal post, previous root canal treatment, internal root resorption ordehydration due to application of irrigating solutions.
As a final result, rootcanals resistence due to functional loads reducee and the roots become morevulnerable to fracture. Therefore, standard principles must be followed duringfilling the root canals. Root canal sealers which are capable of bonding to root dentin can increase the fracture resistance of root canal treated teeth. (2) Fracturesusceptibility for endodonticallytreated teeth are more common then vitalteeth.
The reasons most often reported are -:1. Waterloss upto 11%2. Lossof collagen cross-linking (caused by mechanical debridement )3. Excessivelateral pressure application during obturation 4. Removalof radicular tooth structure during cleaning and shapingTheamount of remaining sound tooth structure and methods of canal preparationdirectly helps to the strength of root canal treated tooth.
From mechanics offracture point of view, the presence of structural defects, cracks, orirregularities of root canals play a major role in determining fracturestrength , because an applied stress may be statistially intensified at the tipof those defects. Affecting factors for potential fracture susceptibility involvesthe dentin thickness, radius of canal curvature as well as external root-morphology. (3) Theuse of Gutta-percha with root canal sealers for obturating root canals hasremained the standard of care in endodontics, despite their inability to achievefluid impervious seal along the dentinal wall of the root canal. ExperimentallyBoth total-etch and self-etch adhesive techniques can reduce apical and coronal leakage as it sealsintra-radicular dentin just before the obturation of root canals with gutta-percha. But these techniquesstill have limitation due to lack ofcopolymerization between the methacrylate-based dentin adhesives, the zinc oxide eugenol or epoxy resin based rootcanal sealer with gutta-percha. (3) Resin-baseddental materials have been proposed in the dentistry to reinforce rootcanal treated teeth with the use ofadhesive sealers in the root canal system. However, studies says that till datebonding agents and resins have problems in working properties, radiopacity andlack of re-treatability when used for endodontic purposes. In modern era, newendodontic obturation material system Real seal (Resilon) which is based onpolyester chemistry which contains bioactive and radiopaque fillers has beendeveloped and tested.
The performance and handling of resilon are similar to Gutta-percha. Inaddition, when used in conjunction with resin-based sealant or bonding agent itforms a mono-block within the canals that bonds to the dentinal walls very welland strengthen the walls against fracture. (3) Therisk factors for fracture predilection in endodontically treated teeth are -:(4)1.Chemical factors: include effects ofendodontic irrigants and medicaments on dentine 2.Microbial factors: include effects of bacteria-dentin interaction 3.Dentin factors: include effects of tooth structural loss 4.Restorative factors: include effects of post and core restorations5.
Age factors: include effects of age changes in dentin Thus,it would be advantageous if the root canal obturation could reinforce the toothand decrease the incidence of root fractures as well. The type of root canalsealer using for endodontic treatment can affect root fracture resistance and also the patternfor root fracture. (3) Aswe know conventional root canal sealers do not bond strongly to dentin andgutta-percha, they do not behave as mechanically homogenous units with the rootdentin. The classical mono-block concept for sealing and reinforcing the rootcanal space was handled with the origin of bondable root filling materials that arerecommended as alternatives to conventional gutta-percha. There is opinion thatadhesion and mechanical inter-locking between the material and root canaldentin will strengthen the remaining tooth structure, and thus reduce the fracture risk. (4) Resilon obturating materialis a polymer-based synthetic material (introduced in 2004) performs similarqualities to gutta-percha and has the same handling characteristics. Thus, thismaterial could be regard as replacement for gutta-percha.
A tight adhesionbetween Resilon cone and resin-based sealer forms a ‘mono-block’ which has potentialto strengthen canal walls against fracture and decrease the micro-leakage.Resilon can be used to reinforce an endodontically treated tooth with combineuse of adhesive sealers in the root canal system. However, as a dental material to reinforce the tooth, theresilon should bond to dentin very well. So, a good dentin adhesive system should have ability to wet and infiltratedentin . (4) Incurrent years, root canal obturationmaterial which is based on polyester chemistry and containing radiopaque and bioactive fillers has beendeveloped as well as tested.
Resilon performs as gutta-percha. When resilon usedin conjunction with resin-based sealantand bonding agent, it forms a mono-block within root canals that bonds to wall of dentin.Because of resin core, sealant anddentin- wall all are ‘attached’ , therefore they have potential to strengthen dentinalwalls against tooth fracture. (5)Realseal is supplied in the same ISO sizes and shapes (in cones and/ or pellets) asgutta-percha. This system can be used with any other obturation technique (eg.
lateralcompaction, thermo-plasticized, in carrier or injectable form). In cone-system, flexibility of resilon is similar to gutta-percha. Based on polyester polymers, Realseal system contains bioactive glass with radiopaque filler particles (eg bariumsulphate and bismuth oxy-chloride ) with approx. 65% of filler content.
Thiscan be softened in presence of heat and also dissolved with many solvents suchas chloroform. This property allows the use of retreatment techniques non-healing cases. Due to it is a resin-based system, resilon is compatible withcurrent restorative techniques in which posts and cores are placed with resin bondingagents. (6) Hence, the aim of this study is ComparativeEvaluation of Fracture Resistance of Root Obturated with Resilon andGutta-Percha Using Two Different Techniques: An in Vitro Study.