A comparison of two methods of adhering composite to metal

Composites are used as an esthetic restorative material in prosthetic dentistry, often with a metallic substructure that provides support when large restorations are required. Different bonding systems have been proposed to occupy the gap between the composite and metal and to reduce marginal leakage at this interface, which with time results in a degradation of the metal-composite junction with dissociation of these two materials. This study compared two methods of adhesion of composite to metal: (1) the Silicoater, based on a silanization of metal and (2) the Spectralink, based on an ionization of metal. A total of 108 metal pellets were covered with composite; 36 pellets formed the baseline or control group and 72 pellets were placed on temporary fixed partial dentures for the 12 patients in the study. The two bonding methods were compared at 0, 30, and 90 days. Marginal leakage (< 0.7 microns) and marginal gap (< 0.6 microns) for the baseline groups were minimal and demonstrated no significant difference between the two samples. The degradation of marginal adaptation and hermeticity was faster and more severe with the pellets of the ionization sample. The Silicoater samples exhibited a better hydrolytic resistance with the formation of a hydrophobic polymer. The degradation of the composite-metal interface with the Spectralink method appeared to be the result of the hydrophilic character of polyfluoromethacrylate. Nevertheless, the values of the marginal gap (< 6.0 microns) and the microleakage (< 30.0 microns) remained low for the metal treatments.