Fracture resistance of RCT-teeth restored with various composite core materials

Objectives: The purpose of this study was to evaluate the fracture resistance of RCT teeth restored with FRC post using 4 resin composite core build-up materials: Tetric N-Ceram, Clearfil Photo Core, MultiCore Flow, LuxaCore Z-Dual. Methods: Thirty-two human lower first premolars were decoronated perpendicular to the root axis at 1 mm above the facial cemento-enamel junction and were endodontically treated. The canals were prepared and inserted with D.T. Light-post No.1 using Panavia 2.0. Samples were randomly divided into 4 groups of 8 teeth, and built up with 4 core materials mentioned above to 6-mm height at facial, and 3-mm at lingual axial wall. The 0.5-mm chamfer was prepared allowing 1 mm of ferrule. The teeth were embedded in acrylic resin blocks with periodontal ligament simulation. The Ni-Cr crowns were fabricated and cemented on the specimens with Panavia 2.0. The fracture resistance was determined using a universal testing machine at 135 degree to tooth axis with crosshead speed of 1 mm/min until failure occurred. Results: The fracture load in Clearfil Photo Core was 709.01 ± 207.22 N, MultiCore Flow was 584.15 ± 166.91 N, LuxaCore Z-Dual was 484.77 ± 88.59 N and Tetric N-Ceram was 456.10 ± 140.06. One-way ANOVA and Bonferroni post-hoc statistical analysis showed that the fracture resistance for Clearfil Photo Core was not significantly different from MultiCore Flow (p>0.05), but significantly higher than that of LuxaCore Z-Dual and Tetric N-Ceram (p<0.05). Conclusion: Among the core materials used in this study, Clearfil Photo Core tended to enhance fracture thresholds of RCT teeth restored with FRC post more than other composites.