A COMPARISON OF 2 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 wh en large restorations are required. Different bonding systems have bee n proposed to occupy the gap between the composite and metal and to re duce 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 composi te 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 m etal pellets were covered with composite; 36 pellets formed the baseli ne or control group and 72 pellets were placed on temporary fixed part ial dentures for the 12 patients in the study. The two bonding methods were compared at 0, 30, and 90 days, Marginal leakage (<0.7 mu m) and marginal gap (<0,6 pm) for the baseline groups were minimal and demon strated no significant difference between the two samples. The degrada tion of marginal adaptation and hermeticity was faster and more severe with the pellets of the ionization sample. The Silicoater samples exh ibited a better hydrolytic resistance with the formation of a hydropho bic polymer. The degradation of the composite-metal interface with the Spectralink method appeared to be the result of the hydrophilic chara cter of polyfluoromethacrylate. Nevertheless, the values of the margin al gap (<6.0 mu m) and the microleakage (<30.0 mu m) remained low for the metal treatments.