The role of oxygen inhibition of a self-etch adhesive on self-cure resin composite bonding

To evaluate the bond strengths on enamel and dentin with a self-etch adhesive (iBond), with or without oxygen-inhibited surface layer, or covered with intermediate self-curing resin, in combination with chemical-cured composite (Core Paste).

Bond strengths on human enamel and dentin (n = 8) were determined according to the following procedures: 1. Adhesive cured under ambient air. 2. Inhibited surface wiped with ethanol. 3. Adhesive cured under nitrogen. 4. Adhesive covered with glycerol during activation. 5. Adhesive coated with glycerol for 1 minute after activation. 6. As 5, but covered for 5 minutes. 7. Cured adhesive coated with intermediate self-curing resin. 8. As 7, but intermediate resin's amine component loaded with anion exchange resin in OH- form. Shear bond strengths (SBS) were measured after 24-hour storage in 37 degrees C water.

SBSs on enamel (7.1 to 25.6 MPa) were, by ranking order (P< 0.05): 4 < 3, 5, 6 < 1, 2, 3, 6 <1, 2, 3, 7 < 1, 7, 8; SBSs on dentin (1.0 to 19.6 MPa): 1, 4, 5, 6 < 1, 2, 6 < 2, 3, 7 < 8. Oxygen inhibition had no adverse effect on enamel bond strengths. On dentin, all groups, apart from the anion exchange resin group (mean 19.6 MPa), showed bond strengths < 8 MPa. Dentin SBS of self-etch adhesive combined with self-cured resin was low, irrespective of the presence of an oxygen-inhibited layer. Deprotonization of the acidic adhesive monomer with an admixed anion exchange compound, added to an intermediate self-cured resin, was effective at overcoming the incompatibility.