Cohesive and adhesive fracture patterns of the composite-enamel bond

A method was developed to adhere composite to a small (1 mm2) surface of human enamel. The geometrical configuration resulted in a complex stress distribution in the vicinity of the composite-enamel bond during fracture in a tension test. The fracture surfaces were examined by scanning electron microscopy. The observed fracture areas at the enamel showed cohesive (composite-composite) as well as adhesive (composite-enamel) parts. The adhesive part of the fracture surface was surrounded by a composite wall. The typical fracture pattern can be explained by the complex stress situation and the deviant structure of the composite near the edge.