Stress distribution of composite resin filling in Class Ⅰ cavity of molars with different cavosurface angle

To analyze the effect of different cavosurface angles on the stress distribution of ClassⅠ cavity composite resin filling of molars through the three-dimensional finite element method and to provide references for the preparation of ClassⅠ cavities.

Three-dimensional finite element models of ClassⅠ composite resin filling of mandibular first molars with three different cavosurface angles (group A: 90°, group B: 120°, group C: 135°) were established. Polymerization shrinkage of composites was simulated with a thermal expansion approach. The mechanical behavior of the restored models in terms of stress and displacement distributions under the combined effects of polymerization shrinkage and occlusal load (600 N) was analyzed.

For ClassⅠ cavities with the same cavity size, the total stress of the restoration model and the maximum stress of the enamel in group A were less than those in groups B and C after cavity composite resin restoration with three cavity cavosurface angles (in which the width of the enamel bevel was 1 mm in groups B and C). The maximum stress of the dentin and adhesive was similar in the three groups, the maximum stress of the composite in group C was the largest, and the maximum stress of the composite in group B was the smallest. In terms of stress distribution, the maximum stress in each restoration model was mainly concentrated in the enamel at the cavosurface, near the enamel-dentin interface and at the edge of the restoration material.

From the point of reducing the stress of residual tooth tissue, the preparation of 90° angle without enamel bevel is an ideal method for cavity preparation when composite resin is used to fill ClassⅠ cavities of molars.