Effect of bonding agents on adhesion of composite resin following CO2 laser etching of dental enamel.

Etching of dental enamel using pulsed carbon dioxide (CO2) laser radiation has been shown to give acceptable bond strengths when hydrophobic enamel bonding resins are used between the lased surface and composite resin. There have been dramatic changes in the composition of bonding agents in recent years. The present laboratory study examined the influence of the bonding agent on the shear bond strength to laser- and acid-etched enamel. Two current generation bonding systems were used (Scotchbond Multipurpose and Optibond). Shear bond strengths in the order of 10 MPa were consistently obtained using laser etching at "optimal" parameters, in the absence of any other preparation of the natural enamel surface. Although there was a consistent trend for shear bond strengths to be greater with Optibond than for Scotchbond MP in both human and porcine test systems, this difference was only statistically significant with acid etching of nonpolished human enamel, and suboptimal laser etching of polished human enamel. Prior surface polishing increased the shear bond strength obtained with maleic acid etching and Scotchbond MP by more than 2-fold, and increased bond strength when Optibond was used following optimal laser etching. These results indicate that both the type of surface preparation and the choice of bonding agent can influence bond strengths to laser-etched and acid-etched enamel.