Effect of furrule and FRC-post diameter in restoring endodontically-treated teeth

Objectives: To evaluate the effect of furrule and FRC post diameter in restoring endodontically-treated teeth using fracture resistance test. Methods: Thirty two extracted human maxillary central incisors were randomly divided for 4 groups (n=8); group 1: ferrule+post fit, group 2: ferrule+smaller post, group 3: no ferrule+post fit and group 4: no ferrule+smaller post. Teeth were cut horizontally for root length 15 mm. Root canal treatment were performed and post space were prepared using DT light drill no.2. In group 1 and 3, teeth were restored with DT light post no.2, while in group 2 and 4 using DT light post no.1. Posts were cemented with resin cement (Panavia F 2.0), core built-up were made with resin composite (Tetric N ceram). Chamfer preparation were performed around the teeth with furrule of 2 mm. in group 1 and 2, but not in group 3 and 4. Ni-Cr crowns were made to fit and cemented with resin cement. Restored teeth were embedded in resin blocks with stimulated PDL. Specimens were loaded on a universal testing machine with crosshead speed 1 mm/min on palatal surfaces, 135 degree to long axis of the tooth until failure occurred. Results: The fracture resistance of group 1, 2, 3 and 4 were 1474.7±285.5 N, 1339.4±120.6 N, 811.7±155.7 N and 668.5±170.2 N, respectively. Two-way ANOVA and Tukey HSD post-hoc analysis revealed that fracture resistance of group 1 and 2 were significantly higher than group 3 and 4 (p<0.05). Significant difference was not found between group 1 and 2 or between group 3 and 4 (p>0.05). Conclusions: Present of ferrule significantly affect the fracture resistance of endodontically-treated teeth restored with FRC post. While using post with smaller diameter did not significantly affect the fracture resistance compared with using post that properly fit to the canal.