Evaluation and comparison of the effect of enamel preparation designs on fracture resistance of micro-filled and nano-filled composite resin: An in vitro study

Abstract

Background and Objectives: The main objective of this study was to compare and evaluate the effect of enamel preparation designs; bevel and stair step chamfer, on fracture resistance of composite resins (micro-filled and nano-filled) using incremental technique. Materials and Methods: The sample group consisted of 60 non-carious maxillary permanent central incisors. They were divided into four groups of 15 teeth each. According to the group, the teeth were prepared and restored with corresponding design and material. The teeth were subjected to compression bending test under instron testing machine then were examined under stereomicroscope. The results were subjected to statistical analysis. Results: Mean peak failure load (Newton) of among experimental groups was observed in the order; Group I (Bevel with micro-filled material) was 255.6 ± 65.0 N and Group II (bevel with nano-filled material) l was 282.1 ± 67.7 N. Group III (Stair-step chamfer with micro-filled material) was 249.8 ± 78.0 N. and Group IV (Stair-step chamfer with nano-filled material) was 283.3 ± 52.0 N. Results of the analysis of variance revealed there was no significant difference in the mean peak failure load values of the four different groups. Failure mode evaluation revealed, majority of the failures occurred as cohesive and mixed type for all the experimental groups. Adhesive type failure was observed maximum (47%) in the bevel group. Stair-step chamfer preparation showed the greatest potential for application, but also involved sacrificing less amount of tooth structure adjacent to fractured edge. Conclusion: This study concludes that both the preparations, bevel as well as stair-step chamfer are equally good to resist fracture when restored either with micro-filled or nano-filled composite resins.