Abstract: Objective: To evaluate the efficiency on smear layer removal of primary teeth after irradiating with 810-nm Diode laser energy at different parameters. Methods: Sixty-six human anterior teeth with apical foramen extracted for retained primary teeth were selected. Samples were randomly divided into negative control group (n=6), positive control group (5.25% sodium hypochlorite, n=6) and experimental groups (Diode Laser, n=54). The experimental groups were divided into 6 subgroups due to different power protocols, including 0.1W, 0.5W, 1.0W, 1.5W, 2.0W, 2.5W, 3.0W, 3.5W and 4.0W. Teeth were subjected to scanning electron microscope (SEM) and the remaining smear layer was evaluated. Results: Diode laser at 1.0W, 1.5W and 2.0W removed the smear layer more effectively at the coronal, middle and apical thirds of root canals respectively, which demonstrated statistically significant differences compared to the lower power groups or the positive group (P<0.05), while these groups showed no significant differences compared to the high power groups. When the power was at 3.0W or more than 3.0W, a few parts of the dentin surface began to fuse. Conclusion: Diode Laser at 1.0-2.5W has a positive effect on removing smear layer of primary teeth and 2.0W is more appropriate.

Key words: Diode , Laser, Primary teeth , Smear layer , Scanning electron microscope (SEM)