Purpose: To evaluate the morphological aspects of dentin surfaces irradiated with different parameters (energy, contact or noncontact, incidence angle) of the Er:YAG laser and determine whether dentin morphology is adversely affected by these parameters. Materials and Methods: Forty-five dentin disks were obtained from extracted third molars. An area of 6 x 9 mm2 was delimited on the dentin surface of each specimen. After that, specimens were randomly divided into 9 groups: G1 – control; G2 – Er:YAG laser at 150 mJ, 90-degree angle, contact mode (38.8 J/cm2); G3 – Er:YAG laser at 70 mJ, 90-degree angle, contact (18.1 J/cm2); G4 – Er:YAG laser at 150 mJ, 90-degree angle, noncontact mode (1.44 J/cm2); G5 – Er:YAG laser at 70 mJ, 90-degree angle, noncontact mode (0.67 J/cm2); G6 – Er:YAG laser at 150 mJ, 45-degree angle, contact mode (37.5 J/cm2); G7- Er:YAG laser at 70 mJ, 45-degree angle, contact mode (17.5 J/cm2); G8 - Er:YAG laser at 150 mJ, 45-degree angle, noncontact (1.55 J/cm2); G9 - Er:YAG laser at 70 mJ, 45-degree angle, noncontact mode (0.72 J/cm2). After irradiation, dentin surfaces were analyzed under scanning electron microscopy (SEM). Results: SEM analysis revealed different surface morphology within the groups evaluated. The contact mode of irradiation and higher energy densities (G2 and G6) produced greater changes on dentin surfaces. Conclusions: Different energy densities and contact/noncontact mode irradiation cause different morphological changes on dentin surfaces. Operators should be aware of the best irradiation settings for a specific clinical application.

Keywords: dentin, energy, Er:YAG laser, incidence angle, morphology