[Polymerization of visible-light cured veneering resins. 3. Influence of conversion on the bond strength of opaque resins].

New light-curable adhesive opaque resins were prepared using 4-methacryloxyethyl trimellitate anhydride (4-META), triethylene glycol dimethacrylate (TEGDMA), di (methacryloxyethyl) trimethylhexamethylene diurethane (UDMA) and titanium dioxide. The purpose of this study was to investigate the relation between the conversion of opaque resins and the bond strengths. Amounts of residual monomers in the bulk-photo-polymerized resins with various compositions were determined by high-performance liquid chromatography. Shear bond strengths of light-cured opaque resins joined to surface-treated Au-Ag-Pd alloy were measured with various primers, components and curing conditions. Photo-polymerized resins which contained mehyl methacrylate (MMA) showed lower conversion compared with bifunctional methacrylate resins. Favorable shear bond strengths were obtained from TEGDMA/UDMA based opaque resins. The opaque resins without MMA bonded strongly to heated and 4-META primed Au-Ag-Pd alloy and 22-23 M Pa strengths were maintained after 20,000 thermocycles. The results revealed that the conversion of MMA with photo-initiater system was lower than that of bifunctional methacrylate, which affected bond strength of opaque resins.