Comparison of the effect of shoulder and contra bevel preparation on fracture resistance of teeth restored with cast posts

Comparison of the effect of shoulder and contra bevel preparation on fracture resistance of teeth restored with cast posts Dr. SA. Shayegh* - Dr. F. Gangy** *- Assistant Professor of Prosthodontics Dept. - Faculty of Dentistry – Shahed University of Medical Sciences. **- Dentist. Background and Aim: Studies concerning the effects of post-core design on fracture resistance of endodontically treated teeth remain controversial. The aim of this in vitro study was to compare the effect of two post-core designs on the fracture resistance of endodontically treated teeth Materials and Methods: Sixty extracted human maxillary central and canine incisors with similar root dimensions were selected for this study. The crowns were sectioned from 4mm above the buccal CEJ line. All crowns were prepared with 1 mm reduction and a chamfer finish line. After mounting and endodontic therapy, the teeth were randomly divided into 3 groups: Group 1 (control): restored with self-cured composite (no posts) Group 2: restored with cast post-cores and a shoulder preparation Group 3: restored with cast post-cores and a contra bevel preparation. Each specimen was subjected to load (N) on the lingual surface at a 135° angle to the long axis with an Instron material testing machine until fracture at a crosshead speed of 2 mm/min. One way analysis of variance and t-test were used to compare the results. Results: The mean fracture resistance for groups 1, 2 and 3 was 534.62 N, 709.38 N and 1395.94 N, respectively. The fractures in group 1 were restorable in 61.5% of the specimens, and in group 2 and 3 in 12.5% of the cases. There were no statistically significant differences between the three groups. Conclusion: Within the limitations of this study neither of the two tested post-core designs, improved the strength of the endodontically treated anterior teeth. Key words: Shoulder - Contra bevel - Post-core - Root fracture