The Photobiomodulation Effect of 940nm Laser Irradiation on Enterococcus faecalis in Human Root Dentin Slices of Varying Thicknesses

Introduction: An increase in dentine thickness could result in an inadequate depth of laser energy penetration. This study aimed to evaluate the effect of a 940 nm laser on Enterococcus faecalis through varying thicknesses of human root dentin slices.Methods: Thirty-five dentin slices of root dentin with thicknesses ranging between 500 and 3000 µm were produced. Six experimental groups (500, 1000, 1500, 2000, 2500, and 3000 µm (n=5 each) were lased and the seventh, non-lased group served as the positive control with a dentine thickness of 2000 µm. The slices were inoculated with 2 µL of E. faecalis suspension of 1.5 × 108 E. faecalis cells/mL. All the lased slices were lased from the opposing side of the inoculation. A non-initiated 200 μm bare end fiber at the power of 1 W, in a continuous wave, was used. Four doses of laser irradiation of 5 seconds with a side-to-side movement with the tip held at a 5o angle to the dentine slice were performed. The colony-forming units of E. faecalis were determined and the bacterial photobiomodulation effect analysed using one-way ANOVA with a Bonferroni and Holm post hoc test at a significance level of P>0.05.Results: There were statistical differences between the dentin slices of 500, 1000, and 1500 μm treated with the laser compared to the positive control (P