Adhesive Bonding of Various Materials to Hard Tooth Tissues. IV. Bonding to Dentin, Enamel, and Fluorapatite Improved by the Use of a Surface-active Comonomer

¹ American Dental Association, National Bureau of Standards, Washington, D.C.

The addition-reaction product of N-phenylglycine and glycidyl methacrylate (NPG-GMA) improved the water-resistant bonding between three direct-filling resin formulations and the surfaces of dentin, enamel, and fluorapatite. Single crystals of fluorapatite were used because they contained no organic material but were similar to hydroxyapatite, the chief mineral of the hard-tooth tissues. Since the NPG-GMA improved the bonding to the fluorapatite surfaces, which contain no organic material, the collagen and other organic constituents of enamel and dentin were not essential to the mechanisms of bonding produced by NPG-GMA. It does not follow, however, that the organic constituents did not play a role in the bonding.

One of the resin formulations, containing vinylsilane-treated, fused-silica particles as a reinforcing filler, gave significantly higher bond strengths than did the control, the same resin prepared with polymer powder instead of silica powder.

Pretreatment of the dentin surface with a 10 per cent solution of EDTA neutralized with sodium hydroxide, before the application of the coupling-agent (NPG-GMA) solution, resulted in a significant increase in the bond strength. After such treatment, the bond strengths to dentin, enamel, and fluorapatite surfaces were 77.4, 54, and 77.4 kg/cm² (1,100, 777, and 1,100 psi), respectively (1-and 3-day immersion).

There was no difference in the average bond strengths when the specimens were immersed in water for 1 day or for 3 days.