Shear bond strength of Nd:YAG laser-irradiated versus acid-etched human enamel

This study was undertaken to evaluate the effect of short-time acid etching after laser irradiation on the shear bond strength. Seventy-five freshly extracted human premolars were used. Laser irradiation was performed with pulsed wave, 200 mJ/pulse and 10 or 15 pps. Group 1: conventional acid etching for 30 s (35% phosphoric acid), Group 2: lased (10 pps) to coated with India ink + acid etching for 10 s, Group 3: lased (15 pps) to coated with India ink + acid etching for 10 s, Group 4: lased (10 pps) to coated with tannin fluoride (Hyc)+ acid etching for 10 s, Group 5: lased (15 pps) to coated with Hyc + acid etching for 10 s. After application of bonding agents, the orthodontic brackets were placed on the buccal surface with orthodontic resin. Shear bond tests at a cross-head speed of 1.0 mm/min were performed. Shear bond strength results were as follows: Group 1 = 6.55 +/- 3.80 MPa; Group 2 = 23.61 +/- 6.44 MPa; Group 3 = 15.83 +/- 6.98 MPa; Group 4 = 18.87 +/- 7.00 MPa; Group 5 = 17.93 +/- 5.71 MPa. The short-time etching after laser irradiation had significantly higher bond strength than conventional acid etching (p<0.001). In the groups coated with India ink, irradiation with 10 pps had significantly higher bond strength than that with 15 pps (p<0.01). These results indicate that short-time etching after laser irradiation enhances the bonding of composite resin to human enamel. (C) 2002 Elsevier Science B.V. All rights reserved.