Effect of 980 nm Diode Laser Irradiation on Dentin Microhardness

Objective: This ex-vivo study evaluated the effect of 980 nm diode laser irradiation on microhardness of radicular dentin in different depths. Method: Seventy-two roots of human canines were randomly distributed into 3 groups (n=24), according to the irrigating solution used in the biomechanical preparation (distilled and deionized water; 1% NaOCl and 1% NaOCl + 17% EDTA), which were subdivided (n=8) according to the laser parameters (no irradiation; 1.5 W/100 Hz and 3.0 W/100 Hz). Laser was applied with helicoidal movements for 20 s. Roots were sectioned in slices and the fragment corresponding to the medium third was submitted to the microhardness test (KHN) at depths of 30, 90, 150 and 300 µm. Results: ANOVA and Tukey-Kramer tests showed that the microhardness values obtained in the irradiated groups with 1.5 W (49.7±11.2) and 3.0 W (50.6±11.9) were statistically similar between themselves (p>0.05) and statistically different (p<0.05) from the non-irradiated group (control) (45.0±9.7), which presented the inferior values. The higher microhardness values were obtained at 150 µm (49.2±11.0) and 300 µm (52.3±11.3), which were statistically similar between themselves (p>0.05) and statistically different (p<0.05) from the depth of 30 µm (44.4±10.5). Conclusions: The microhardness of the radicular dentin increased after the irradiation with 980 nm diode laser.