Thesis (M.Sc.)--Chulalongkorn University, 2011

Background and rationale: Different core materials may have an influential effect on the fracture resistance of endodontically treated teeth (ETT) with flared root canals Objective: This study compared the fracture resistance of endodontically treated teeth with flared root canals, restored using core build-up materials with different modulus of elasticity and a quartz fiber post. Material and methods: Thirty two extracted human mandibular premolars were decoronated to obtain 15 mm of root length, endodontically performed and prepared as flared canal with 1 mm of dentin thickness wall to the depth of 7.5 mm into root. All teeth were restored with D.T. Light post #1 and luted with Super-Bond C&B resin cement and then randomly divided into 4 groups (n=8). Four core build-up resin composites: Clearfil Photocore, Multicore Flow, Built-it and Coreflo were used as core foundation. The specimens were embedded in self-cured acrylic resin blocks with a simulated PDL. All specimens were loaded on a universal testing machine with a crosshead speed of 1 mm/min on the buccal surface at an angle of 135๐ to the long axis of the tooth until failure occurred. Results: The fracture resistance of groups 1, 2, 3 and 4 were 864.7 ± 189.8 N, 1519.2 ± 278.9 N, 1110.8 ± 229.8 N, and 901.6 ± 183.6 N, respectively. One-way ANOVA and Tukey HSD post-hoc analysis revealed the fracture resistance of groups 1 was significantly higher than group 2, 3 and 4 (p<0.05). No significant differences were found in groups 2, 3 and groups 4. Conclusion: Within the limitation of this study, Multicore Flow showed better fracture resistance in flared canals with favorable fracture.