Abstract
Three isomers of methacryloyloxybenzoic acids(MBA)were synthesized to be applied to dental adhesive resin.The tooth-adhesiveness of the self-curing resins containing MBA isomers was evaluated by measurements of their tensile bond strengths.The adhesion promoting mechanism of MBA isomers was examined with respect to their adsorption behaviors onto tooth powders from MMA and by scanning electron microscopy.(SEM)There were appreciable concentrations of MBA in MMA for the o-and m-isomers(2-MBA and 3-MBA, respectively).At 3〜5% of 2-or 3-MBA concentrations, the maximum bond strengths of 14〜15MPa to teeth that were treated with 10% citric acid-3% FeCl3 solution were obtained by the TBB-O initiated resin.Although the p-isomer(4-MBA)showed very limited solubility to MMA at room temperature, the 1% 4-MBA resin yielded 12.5〜14.5MPa of bond strength to treated teeth.The adhesion promoting effects of MBA isomers were also observed when other polymerization initiating systems such as benzoyl peroxide-tertiary aromatic amine with or without aromatic sulfinate, were employed, and when teeth were not treated.3-MBA may be the best for dental adhesive among the isomers because of its higher solubility to other monomers and superior adhesive stability estimated by long-term immersion and thermocycling tests.SEM revealed that the formation of the resin-infiltrated dentin layer is closely associated with the bond strength to treated dentin, and that MBA promoted the monomer infiltration into demineralized dentin layer.In adsorption to tooth surfaces, MBA was preferentially adsorbed from MMA solution by its carboxyl group with the orientation of the phenyl group being far apart from the tooth surface.The adsorption isotherms suggested that there was competitive adsorption of MBA with MMA to the MBA adsorbed layer.Therefore, the adhesion promoting mechanism of MBA may be as follows:MBA is readily adsorbed to tooth surface from MMA.The MBA adsorbed draws closely the monomers in the adhesive composition toward the tooth surface, or facilitates their hybridization with treated dentin.
