Clinical research on bonded amalgam restorations. Part 1: SEM study of in vivo bonded amalgam restorations.

Exfoliated deciduous teeth, in which bonded or nonbonded amalgams had been placed two to three years previously, were examined directly and indirectly with the use of a scanning electron microscope (SEM). Bonding resin was found in the interface between the amalgam and the tooth structure, frequently obliterating the microspace. Several materials now are available that bond amalgam to tooth surfaces with bonding strength exceeding 10 MPa. Amalgam can be retained in preparations without undercuts, or in pits and fissures without any tooth preparation. The article consists of two parts: in part 1, results of a pilot study on bonded amalgam-tooth interfaces is presented. In part 2, the authors discuss further studies and clinical technique. Commercial products are compared; and other clinical trials now in progress, concerning amalgam bond strength adhesion and ability to eliminate microspace, are discussed.