Previous studies have shown the effects of Er,Cr:YSGG laser irradiation on the dentin bond strength; but there are few reports that show the significance of the irradiation with different laser parameters on dentin bond strength and interface morphology. This in-vitro study attempted to evaluate the microtensile bond strength (mu TBS) and interface morphology of resin-dentin interfaces, either followed by treatment with Er, Cr: YSGG laser irradiation with different parameters or not. The flattened dentin samples of 35 bovine teeth were embedded into acrylic blocks and randomly divided into seven groups according to surface treatments using Er, Cr: YSGG lasers with different parameters: 3 W/20 Hz, 3 W/35 Hz, 3 W/50 Hz, 1.5 W/20 Hz, 1.5 W/35 Hz, 1.5 W/50 Hz, or no laser treatment (n = 5). Composite buildups were done over bonded surfaces and stored in water (24 hours at 37 degrees C). Specimens were sectioned into sticks that were subjected to lTBS testing and observed under FE-SEM. Control groups (27.7 +/- 67.0) showed statistically higher values than laser-irradiated groups. There were no significant differences among laser groups. Despite that, increasing the pulse frequency yielded slightly higher bond strength. Depending on laser settings, Er, Cr: YSGG laser irradiation caused interfacial gaps and resin tags with wings morphology. With the parameters used in this study, Er, Cr: YSGG laser irradiation promoted morphological changes within resin-dentin interfaces and negatively influenced the bond strength of adhesive systems. (C) 2015 Wiley Periodicals, Inc.