FRACTURE RESISTANCE OF CLASS II (MOD) RESTORATIONS: INFLUENCE OF RESTORATIVE TECHNIQUE AND BEVEL PREPARATION? ? AN IN-VITRO STUDY

Background and Objectives: Composite resins have heralded a new era in restorative dentistry. Although clinicians have been using resin based composites successfully to restore posterior teeth in class II situations for several years, creating a functional, anatomical proximal contact remains a clinical challenge. Therefore, this in-vitro study evaluates the effects of restorative technique, bevel and thermal cycling on the fracture resistance of newer generation composite resin MOD restorations. Materials and Method: The selected specimen teeth (forty four premolars) were randomly sampled into eight teeth in four experimental groups and six teeth in two control groups with one group of intact teeth and other group with prepared cavity but no restoration. The experimental groups included two groups of direct composite restoration and another two groups of indirect composite restoration, with and without bevel preparations. These specimens were subjected to fracture strength study under compression and statistically analyzed using Kruskal Wallis Test and Mann?Whitney ?U? Test. Results: The mean compressive load required to fracture the specimens was maximum in Group I (389.2 N) and minimum in Group III (163.7 N). Group comparison showed that there was no significant difference among the groups for the load values whereas there was significant difference among the groups for the deformation values. Inter-comparison among the groups was done. For the load values, Group I showed high significance when compared to Group III, and Group II showed significant difference when compared to Group VI. For the deformation values, Group I showed significant difference when compared to Group III, Group II showed significant difference when compared to Group III, Group II showed significant difference when compared to Group VI and Group III showed significant difference when compared to Group VI. Interpretation and Conclusion: Within the limitations of this in-vitro study, inlay cavity preparations resulted in higher removal of tooth structure compared to direct composite probably due to the proximal flare required to remove the undercut in indirect restorations. Fracture strength was inversely proportional to the amount of the tooth structure removed. Direct composite preparations had higher resistance to occlusal load fracture than indirect restorations.