Adhesive Bonding of Various Materials to Hard Tooth Tissues. II. Bonding to Dentin Promoted by a Surface-active Comonomer

Abstract

The strength of bonds between a direct-filling acrylic resin and dentin surfaces, tested in tension after soaking for 20 hours in water, was only 0-1.4 kg/cm2 (0-20 psi) when the dentin was treated with one of the following: nothing; cavity primer; cavity seal; ethanol; or 5 per cent ethanol solutions of oleic acid, China wood fatty acid, and N-phenylglycine. A quick-setting and a general-purpose epoxy resin gave similar results. A surface-active comonomer, the addition-reaction product of N-phenylglycine and glycidyl methacrylate (NPG-GMA), was synthesized for use as a coupling agent between the resin and the substrate. When a 5 per cent ethanol solution of NPG-GMA was applied before the methacrylate resin, the average tensile strength of the bond was between 10.5 and 22.5 kg/cm2 (150 and 320 psi)-a significant improvement. Reapplication of this NPG-GMA solution and resin without resurfacing between tests gave successively increasing values to 46 kg/cm2 (660 psi), which dropped significantly when the same specimens of dentin were resurfaced, following this series of tests, before reapplication of the NPG-GMA solution. Whether this further increase was due to incremental removal of a fractured surface layer, to an increase in the population density of NPG-GMA molecules on the substrate surface, or to other reasons should be determined. The author is grateful to Mr. R. W. Morris and Miss M. K. Wharton for assisting in the experimental work. © 1965, SAGE Publications. All rights reserved.