Background: High concentrations of acidic monomers in adhesives can inhibit proper polymerization at the interface with self-curing composites.
Purpose: This study aimed to evaluate the effect of three oxygen-inhibited layer (OIL) removal methods on the micro-shear bond strength (µSBS) of dual-cure and self-cure composites to dentin using a two-step self-etch adhesive.
Materials and Method: In this in vitro study, forty bovine incisor crowns were mounted in acrylic resin. Dentin surfaces were abraded with 600-grit silicon carbide paper to create a standardized smear layer. Experimental groups included using a two-step self-etch adhesive (Clearfil SE Bond), curing it, and then dividing it into four groups: (1) control (no preparation after adhesive application) and subsequent groups including removal of the OIL with (2) cotton wool soaked in ethanol, (3) cotton wool soaked in pumice, and (4) blocking air with glycerin and re-irradiation. Light-cure (Clearfil APX), self-cure (Alpha-Dent Self Cure Composite), and dual-cure resin cement (Duo-Link Universal Adhesive) were placed in cylindrical molds made of transparent polyethylene tubes (120 total, 30 per group) on dentin. The µSBS of the samples was measured after thermocycling.
Results: In the light-cure composite, µSBS did not differ significantly in any group compared to the control. In the dual-cure composite, only the alcohol group showed a significant decrease in bond strength compared to the control. In the self-cure composite, all OIL removal methods significantly improved bond strength compared to the control.
Conclusion: Although removing the OIL improved bond strength in self-cure composites, it failed to achieve values comparable to light-cure groups. For dual-cure composites, OIL removal is unnecessary and potentially detrimental.