Thesis (M.Sc.)--Chulalongkorn University, 2010

Fracture resistance in endodontically treated teeth may be different depending on the type of core build-up material used. The purpose of this present study was to evaluate the fracture resistance of endodontically treated teeth restored with fiber reinforced post using 4 resin composites as core build-up materials: Tetric N-Ceram, Clearfil Photo Core, MultiCore Flow, LuxaCore Z-Dual Automix. Thirty-two human lower first premolar teeth were decoronated perpendicular to the root axis at 1 mm above the facial cementoenamel junction )CEJ( and the roots were endodontically treated. All specimens were prepared and inserted with D.T. Light-post Illusion (size 1) using dual-polymerizing resin cement (Panavia F2.0). Samples were randomly divided into 4 groups of 8 teeth and built up with 4 core materials mentioned above. The resin composite cores were bonded to dentin using a dentin bonding agent according to manufacturers’ recommendation. Each specimen was prepared with a 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 autopolymerizing acrylic resin blocks with periodontal ligament simulation. The Ni-Cr alloy crowns were fabricated and cemented on the specimens with Panavia F2.0. The fracture resistance was determined using a universal testing machine at 135-degree angle to the long axis of each tooth with a crosshead speed of 1 mm/min until failure occurred. The highest fracture load of each specimen was recorded. It was found that the mean fracture loads was highest in Clearfil Photo Core (709.01 ± 207.22 N), followed by MultiCore Flow (584.15 ± 166.91 N), LuxaCore Z-Dual Automix (484.77 ± 88.59 N) and Tetric N-Ceram (456.10 ± 140.06 N), respectively. One-way analysis of variance (ANOVA) and Bonferroni multiple comparisons test 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 Automix and Tetric N-Ceram (p<0.05). Among the cores used in this study, Clearfil Photo Core tended to enhance fracture thresholds of teeth restored with fiber post more than other composites.