In vitro comparison of cuspal fracture resistances of posterior teeth restored with various adhesive restorations

Purpose: This study compared the cuspal fracture resistances of posterior t eeth restored with five different adhesive restorations. Materials and Meth ods: Eighty-four sound human molars were included in this study. Sample mol ars were divided into seven groups. The first five groups received mesio-oc clusodistal cavity preparations and were restored with (1) amalgam combined with urethane dimethacrylate cement, (2) posterior composite, (3) direct c omposite inlay, (4) cast-metal inlay, and (5) complete ceramic inlay. The s ixth and seventh groups were introduced in the study as controls. Samples o f group 6 were prepared but were tested without restoration (prepared-only group). Samples of group 7 were intact teeth and were tested as unprepared. All samples were loaded axially until failure. Results: While the unprepar ed teeth had a significantly higher resistance than all other groups, the p repared-only teeth were the weakest. No significant differences were found in resistance to cuspal fracture among the restoration groups. Conclusion: The difference between the mean cuspal fracture resistance of the unprepare d and prepared-only groups was statistically significant. Restoration group s were stronger than the prepared-only group. However, differences between the restoration groups were insignificant.