Effect of 980 nm diode laser on root canal permeability

Objective: This study evaluated the effect of the 980 nm diode laser wavelength at different parameters on the permeability of root canal dentine when associated with different irrigating solutions. Methods: Seventy-five human mandibular canines were sectioned at 15 mm from the apex, rotary instrumented up to a # 40 .02 file and irrigated with 2 ml of distilled water between files. After final preparation, the teeth were randomly divided into 3 groups and received a final irrigation with 10 ml of the following solutions: I - distilled water, II - 1% sodium hypochlorite, and III - 17% EDTAC. A final flush with 10 ml of distilled water was repeated to eliminate trace solution. Diode laser was then applied at 1.5 or 3.0 W as either a continuous wave (CW) or a pulsed wave (100 Hz). The teeth were then processed histochemically with 10% copper sulfate and 1% rubeanic alcohol-acid solutions, clarified in xylol, machine sectioned under water-spray at 70 µm and the percentage of cooper ion penetration in the dentin counted. Data were analyzed statistically with the Tukey-Kramer test (p<0.01). Results: The results depended on the solution used for final irrigation. When laser was associated with water an increase in permeability was found (7.96 ± 0.700 vs 10.28 ± 0.880), when associated with EDTAC permeability decreased (14.84 ± 1.272 vs 7.04 ± 0.776) and with NaOCl it was not changed (8.74 ± 0.838 vs 8.30 ± 1.175). Conclusions: The 980 nm diode laser caused either an increase or decrease in dentine permeability depending on the irrigating solution used and consequently the composition of the remaining canal dentine after irrigation.