Influence of sodium hypochlorite on Er:YAG laser-irradiated dentin and its effect on the quality of adaptation of the composite restoration margins.

OBJECTIVE The aims of this in vitro study were to evaluate: (1) the influence of 5% NaOCl application on Er:YAG-irradiated dentin; and (2) its effect on the quality of adaptation of the composite restoration margins. BACKGROUND DATA Previous research has shown that Er:YAG dentin irradiation produces a thermally affected tissue layer that results in lower bond strength than that of nonirradiated dentin. The removal of this thermally-affected layer may enhance the quality of dentin bonding. MATERIALS AND METHODS Forty-nine caries-free extracted human molars were transversely sectioned in order to totally expose the dentin. Four standardized cavities were created on the dentinal surface of each molar. First, two cavities were irradiated with Er:YAG laser (2.94 nm): 150 mJ, 10 Hz, variable square pulse (VSP) mode (100 μsec), beam diameter=0.9 mm, speed of irradiation=1 mm/sec, 20% air and 20% water. Then, one of irradiated cavities and one of nonirradiated cavities were treated for 30 sec with 5% NaOCl solution. Finally, they went through a standard bonding treatment for composite restoration, etching, bonding, and composite filling. We obtained four groups of cavities: (1) one control group of nonirradiated cavities not pretreated with NaOCl; (2) one group of nonirradiated cavities, pretreated with NaOCl; (3) one group of irradiated cavities, not pretreated with NaOCl; and (4) one group of irradiated cavities, pretreated with NaOCl. All samples were subjected to thermocycling. Every cavity was immersed into a 0.5% solution of methylene blue. The percentage of dye penetration (microleakage) in the composite-dentin interface was evaluated. Six molars were analyzed by scanning electron microscope. RESULTS Dye infiltration depth was significantly reduced in irradiated cavities treated with 5% NaOCl solution. CONCLUSIONS The application of a 5% NaOCl solution on Er:YAG irradiated cavities can significantly improve the marginal quality of composite bonding.