Role of cusp coverage in the protection of unsupported enamel in posterior composite restorations

Role of cusp coverage in the protection of unsupported enamel in posterior composite restorations Dr. A. Pahlavan* /Dr. AH. Taheri** *-Assistant professor of Operative Dentistry Dept-Faculty of Dentistry- Tehran University of Medical Sciences. **- Dentist. Background and aim: Removal of unsupported enamel is one of Block's important principles in cavity preparation. The aim of this study was to determine the effect of bonding materials in the protection of unsupported enamel and sound tooth structure. Materials and Methods: In this sound,30 sound mandibular molars were selected. After cusp reduction, a 3mm depth occlusal cavity with walls consisting of pure unsupported enamel of 3mm height, was prepared. The samples were divided into two groups. In the first group, the cavities were filled by composite. In the second group, the cavities were filled like the first group and the unsupported enamel surfaces were then etched extending 2mm buccocclussally and enamel dentin bonding was applied. The surfaces were finally covered by composite and light cured. The compressive strength of both groups were evaluated by an instron machine. Results: Date were subjected to t-student test for analysis. The mean required force to break unsupported enamel was 3440N/mm2 in the first group and 4213N/mm2 in the second group showing the effective role of etching and buccal coverage of enamel in the protection of remaining weak enamel. Conclusion: The findings of this study suggest that the application of adhesives and coverage of the buccal surfaces support the weak enamel and dentin walls. Key Words: Composite , Unsupported enamel , Cuspcoverage.