Effect of Reinforcement on the Fracture Resistance of Endodontically Treated Molars by Various Bonded Restorations -An in Vitro Study

To compare and evaluate the fracture resistance of endodontically treated molars reinforced with various bonded restorations and to study the type of fractures in various restorations. Methods: Forty extracted mandibular molars were endodontically treated. MOD (Mesio-Occluso-Distal) cavities were prepared and Mesio-Buccal cusp was reduced in all to provide cuspal coverage. All the teeth were then divided into 4 groups. The cavities in group 1(control) were filled with high copper amalgam. Group 2 was restored with direct resin composite. In group 3 after the priming and bonding procedures as in group 2, cavity surfaces were coated with flowable resin composite. Before curing a piece of polyethylene ribbon fiber was cut and coated with adhesive resin and was embedded inside the flowable composite. The resin composite was cured with visible light cure (VLC) gun. For group 4, restorations were done according to the recommendations provided by the manufacturers of SR Adoro (Ivoclar-Vivadent, Schaan, Liechtenstein) composite material. Compressive fracture strength test was performed after at least 24 hours of the fabrication of the specimens, by application of compressive loading in a Universal testing machine, applied on the occlusal aspect of each specimen with a steel bar. The mean loads necessary to fracture were recorded in Newton and the results were statistically analyzed. Results: Group 4 (indirect composite inlay) had the greater fracture resistance and group 1(Amalgam) had the poorest. Difference between group 1 and 3, group 1 and 4, group 2 and 4 were statistically significant. No statistically significant difference was found between group 1 and 2, group 2 and 3, group 3 and 4. Predominant type of fracture in group 1 and 3 was fracture of tooth below cemento enamel junction at tooth restoration interface without mesio buccal cusp involvement. In group 2 and 4, predominant fractures were of tooth below cemento enamel junction through center of restoration without mesio-buccal cusp involvement.