Fracture resistance of endodontically treated teeth restored with various lengths of fiber reinforced post; with and without ferrule

Abstract

Introduction: Endodontically treated teeth (ETT) often lack of coronal tooth structure. The ferrule effect has been shown to provide positive reinforcement to ETT by resisting the leverage of occlusal force. However, another study reported that the presence of tooth structure coronal to finishing lines did not enhance fracture resistance. Moreover, the restoration of FRC posts with metal crowns with or without ferrule was not significantly different in fracture resistance. It was also demonstrated that the placement of a metal crown may obscure the effect of different post and core buildup techniques. Conflicting reports about ETT with presence of ferrule, and final restorations were found among the literatures. Objectives: To clarify the effect of fiber reinforced composite post length on the fracture resistance of ETT restored without crown and to investigate the effect of ferrule and the full coverage metal crown on the fracture resistance of ETT. Methods: Four groups based on different post length with n=6 in each group; crown height(C)/post length(P) ratio 1:2, C/P 1:1, C/P 2:1, and prepared extracted teeth (PET) were evaluated. Three groups based on ferrule and full coverage metal crown with n=6 in each group; metal crown with ferrule (MC/F), metal crown without ferrule (MC/NF), composite resin coverage with ferrule (CR/F) in combination with previous C/P 1:2, and PET groups were also compared. This study used experimental fiber reinforced composite posts containing glass fibers with a parallel configuration, a diameter of 1.5 mm, and modulus of elasticity of 18 GPa luted with resin cement (Panavia F 2.0). Cervical dentin was conditioned with self-etching bonding agent (Clearlfil SE bond). The core was built-up with composite resin (Clearfil Photocore). The metal crowns were luted with resin cement. An oblique compressive load was applied using the universal testing machine. Results: There was no significant difference in fracture resistance among different post length (P>0.05). The crown/post ratio of 1:2 generated more specimens with restorable mode of failure. Additionally, the MC/F group demonstrated the highest fracture resistance compared to the others (P<0.05). Conclusion: Within the limitation of this study, post lengths did not influence the fracture resistance but demonstrated in the more favorable fracture mode in C/P ratio of 1:2 group. MC/F group presented with the highest fracture resistance compared to the others.