Figure 4. Equivalent stress distribution of composite resin in the three groups a-c: distribution of equivalent stress of composite resin, with the maximum stress in each restoration model mainly concentrated at the edge of the restoration material; d-f: distribution of equivalent stress of composite resin in the buccolingual direction; g: maximum stress of composite resin; group A: the cavosurface angle is 90°; group B: the cavosurface angle is 120°; group C: the cavosurface angle is 135°