1990 Volume 2 Issue 2 Pages 133-141
An experimental self-etching dentin primer, prepared by dissolving an acidic monomer, methacryloxyethyl succinate (MES), dimethacryloxyethyl phosphate (DMEP) or tertiarybutyl acrylamide sulfonic acid (TBAS), in an aqueous solution of 2.9M 2-hydroxyethyl methacrylate (HEMA), has been shown to promote adhesion by a bonding agent between a composite resin and dentin. To clarify the mechanism of this promotion we examined the effects of acidic monomers on dentin cleansing, surface tension of water and hypotonic hemolysis of rat erythrocytes. In scanning electron microscope observation of the dentin surface, the smear layer remained slightly evident after MES-HEMA treatment. DMEP-HEMA or TBAS-HEMA caused complete removal of the smear layer, and openings of dentinal tubules were clearly evident. MES and DMEP, 1×10-6 M and 1×10-4 M, respectively, decreased the surface tension of distilled water (72 dyne/cm) . The surface tension depression by 0.3M HEMA was apparently not further affected by MES, DMEP or TBAS at 1×10-7 to 1×10-2M. The osmotic pressure of hypotonic buffer was increased by MES, DMEP, TBAS and HEMA at concentrations greater than 1×10-2M. The hypotonic hemolysis of erythrocytes was inhibited by MES and TBAS at 4×10-3 to 1×10-2M and by HEMA at 4×10-1M. DMEP promoted hypotonic hemolysis at 4×10-5 to 1×10-4M, but caused inhibition in the concentration range of 4×10-4 to 1×10-3M. The protective effect of acidic monomers on the erythrocytes was promoted by the presence of 0.1 M HEMA, while DMEP at 1×10-2 M showed only a lytic effect. These results suggest that the mechanism of promotion of the adhesive ability of a bonding agent by self-etching dentin primers containing these acidic monomers is related to the increased surface activity of water and membrane stability of erythrocytes, since these effects of acidic monomers might be caused by the reduction in surface tension of secretion from dentin and inhibition of secretion from dentinal tubules.
