Effect of different cavity configurations on the tensile bond strength of hybrid and nanofilled composites - in vitro study

Background: This study was undertaken to evaluate the effect of various cavity configurations on the tensile bond strength of hybrid and nanofilled composites. Materials and Methods: In this in vitro study eighty extracted molars of the permanent dentition were divided into two main experimental and two control groups (Group I & Control I - Hybrid composite; Group II & Control II - Nanofilled composite). Cavity of 2mm depth and 3mm, 4mm and 6mm diameter was prepared for each experimental group. Accordingly, group I and II were divided into 3 subgroups (n = 10). The teeth were restored with self etch adhesive and Hybrid & Nanofilled composite as per the experimental groups. For the control group specimens, teeth were grounded to expose the dentin surface and the additional composite was placed on the flat surface. All restored teeth were sliced to produce 1mm thick sections which were then trimmed into an hour glass shape with the narrowest portion at the adhesive interface. The specimen was tested for tensile strength at a cross head speed of 1mm/min. Results: In both the groups 3mm diameter samples showed less strength as compared to the 4mm and 6mm diameter samples. Control groups showed significantly better strength as compared to the experimental groups. (p< 0.001) Conclusion: C-factor affects the tensile strength upto certain limit. Flat surface showed better tensile bond strength as opposed to the cavities. Nanofilled composite showed equal or higher tensile bond strength as compared to the hybrid composite.