Effect of Er: YAG laser on dentin adhesion of self-etch and total-etch bonding systems in two coronal and radicular sections

Er:YAG lasers are effective in removing dental tissues and in tooth surface preparations for adhesive procedures. The aim of the present study was to evaluate the efficacy of Er:YAG lasers in improving the bond strength of composite resins to coronal and radicular dentin with the use of two self-etch and total-etch adhesive systems. In this in vitro study, 60 sound human premolars were randomly divided into 5 groups of 12. The teeth were cut at CEJ using diamond disks to yield two subgroups of coronal and radicular sections. Surface preparations were carried out by Er:YAG laser (4 Hz, 160 mJ). A total-etch adhesive was used with or without phosphoric acid, and a self-etch adhesive was used on the surface. Two other groups were used as controls, in which diamond burs and bonding systems were used for surface preparation. Composite resin cylinders (Z250, 3M ESPE) were bonded to the samples and stored in distilled water at 37ºC for 24 hours. Means of shear bond strength values were measured in a universal testing machine. Data was analyzed with t-test (α = 0.05). There were no significant differences in the means of shear bond strength of coronal and radicular sections between the subgroups (p value > 0.05). Self-etch adhesive system had the highest means of bond strength in both the laser and bur groups, with a significantly higher bond strength compared to the total-etch adhesive system (p value < 0.05). In the total-etch system, surface conditioning with laser was less efficacious than acid etching (p value < 0.05). Dentin surface preparation with Er:YAG laser is effective on the bond strength of composite resin to dentin, depending on the type of the bonding system used; with the laser application, self-etch adhesive system exhibits more bond strength decrease compared to the total-etch system. In addition, acid etching of the laser-treated dentin significantly improves the efficacy of total-etch adhesive systems.