Biologicalaim for root canal therapy is to prevent and/or eliminate apical periodontitis.Elimination of apical periodontitis can be achieved by chemo-mechanical debridementof canal walls followed by final obturation. Ideal role for root canal fillingmaterial 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 apicaland lateral gaps in the root canal system and adaptation to the dentinal canalwalls are the favourable condition of ideal sealers. In cases such as, thinning and weakening of rootcanal walls may occur due to excessive pressure during root canal cleaning andshaping, over-instrumentation, removal of intracanal post, previous root canaltreatment, internal root resorption or dehydration due to the application ofirrigating solutions.
As a result, resistance of root canals of the tooth tofunctional loads may decrease and the roots become more susceptible to fracture.Therefore, standard principles must be followed during filling the root canals.Rootcanal sealers which are capable of bonding to root dentin can increase thefracture resistance of endodontically treated teeth.
(2) Thefracture susceptibility of endodontically treated teeth are more common when compare to the vital teeth.The reasons most often reported are -:1. Waterloss upto 11%2. Lossof collagen cross-linking due to 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, or canalirregularities play a major role in determining fracture strength , because anapplied stress may be exponentially amplified at the tip of those defects. Influencingfactors for potential fracture susceptibility involves the dentin thickness,radius of canal curvature as well as3 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 adhesives techniques are found to reduce apicalas well as coronal leakage as it seals intra-radicular dentin just before theobturation of root canals with gutta-percha.S till these techniques havelimitation due to lack ofcopolymerization between the methacrylate-based dentin adhesives, the epoxyresin or zinc oxide eugenol-based root canal sealer, and gutta-percha.
(3) Resin-baseddental materials have been proposed in the dentistry to reinforce anendodontically treated tooth with the use of adhesive sealers in the root canalsystem. However,studies says that till date bonding agents and resins haveproblems in working properties, radiopacity and lack of re-treatability whenused for endodontic purposes. In recent years, new endodontic obturationmaterial Resilon based on polyester chemistry which contains bioactive andradiopaque fillers has been developed and tested.
The performance and handlingof this material are similar to Gutta-percha. In addition, when used inconjunction with a resin-based sealant or bonding agent it forms a mono-blockwithin the canals that bonds to the dentinal walls very well and strengthen thewalls 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 therapy may affect root fracture resistance and thepattern of 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 rek4ndled with the advent of bondable root filling materialsthat are advocated as alternatives to conventional gutta-percha. There isthought that adhesion and mechanical interlocking between the material and rootcanal dentin will strengthen the remaining tooth structure, and thus reduce fracture risk. (4) Resilon obturating materialis a synthetic polymer-based material (introduced in 2004) performs similarqualities to gutta-percha and has the same handling characteristics. Thus, thismaterial could be considered as replacement for gutta-percha.
A tight adhesionbetween Resilon cone and resin-based sealer form a ‘mono-block’ and has potentialto strengthen the walls against fracture and decrease the micro-leakage.Resilon was used to reinforce an endodontically treated tooth through the useof adhesive sealers in the root canal system. However, for a dental material toreinforce the tooth, the material should bond to dentin very well.
So, anessential attribution for a good dentin adhesive system is the adhesive’s abilityto wet and infiltrate dentin. (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)Resilonis supplied in the same ISO sizes and shapes (in cones and/ or pellets) as gutta-percha.According to manufacturer, this may be used with any other obturation technique(eg. lateral compaction, thermo-plasticized, in carrier or injectable). In cone form, the flexibility ofthis material is similar to gutta-percha.
Based on polyester polymers, Resilon contains bioactive glass with radiopaquefillers (barium sulphate and bismuth oxy-chloride ) with approx. 65% of fillercontent. This can be softened in presence of heat and also dissolved with many solventssuch as chloroform. This property allows the use of retreatment techniques non-healing cases. Due to it is a resin-based system,resilon is compatible with current restorative techniques in which posts andcores are placed with resin bonding agents.
(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.
