This study evaluated (1) the micromorphology by scanning electron microscopy (SEM) and (2) the adhesive performance by microtensile bond strength (μTBS) of diamond bur-treated dentin compared to Er:YAG laser-treated dentin of human primary teeth. (1) For qualitative SEM evaluation, dentin of 18second primary molars (n = 3/method) was treated with either diamond bur as a control (group 1a: 40μm diamond bur only (clinical situation); group 1b: grinding + 40μm diamond bur) or with Er:YAG laser (group 2a (clinical situation, manufacturer's settings): 200mJ/25Hz (5W) + 100mJ/35Hz (3.5W) laser only; group 2b (experimental setting "high"): grinding + 400mJ/20Hz (8W); group 2c (manufacturer's setting "finishing"): grinding + 100mJ/35Hz (3.5W); group 2d (experimental setting "low"): grinding + 50mJ/35Hz (1.75W)). (2) For evaluation of adhesive performance, 64second primary molars were divided into four groups and treated as described for group 1b and groups 2b/c/d (n = 16/method), and μTBS of Clearfil SE/Clearfil Majesty Esthetic to dentin was measured. The SEM micrographs were qualitatively analyzed. The μTBS values were compared with a Kruskal-Wallis test. The significance level was set at α = 0.05. SEM micrographs showed the typical micromorphologies with a smear layer for the diamond bur groups and open dentin tubules for all laser-treated groups. However, in group 2d, the laser beam had insufficiently irradiated the dentin area, rendering the underlying ground surface partly visible. There were no statistically significant differences between μTBS values of the four groups (p = 0.394). This suggests that Er:YAG laser treatment of dentin of primary molars provides bond strengths similar to those obtained following diamond bur treatmen
