Influence of Er, Cr and Diode-980nm lasers on the microhardness of root dentin after cariogenic challenge

Root caries is an oral health condition characterized by the demineralization of the root surfaces of teeth. It is particularly common among elderly populations. Lasers have proven to be quite effective in treating root caries, with varying effects depending on the laser parameters and the target tissue. Thus, aim of this article was to evaluate the influence of Er,Cr laser irradiation and 980 nm diode laser application, with or without fluoride treatment, on the microhardness of root dentin.

Eigthy-bovine incisors were selected (4mm x 4mm x 3mm-thickness) and divided into 8 groups (n=10). NT: no treatment (negative control); FG: Fluoride gel (2%NaF); Er,Cr: Er,Cr: YSGG; Er,Cr+FG; FG+ Er,Cr; Di: 980 nm diode laser; Di+FG; FG+Di. The parameters Er,Cr:YSGG laser were as follows: 0.25 W; 5.0 Hz; 4.46 J/cm2 without water and 55% air. Furthermore, the 980-nm diode laser parameters were 2.0 W; 2.0 Hz; 21.41 J/cm2. Half of each specimen was isolated (control area) and the other half received one of the treatments proposed after to pH cycling during for 15 days to simulate a high caries risk environment, followed by longitudinal microhardness analysis (Knoop) under a load of 30 gf for 30 seconds. Microhardness percentage values were analyzed using the non-parametric Kruskal-Wallis test, followed by Dunn's post hoc test for pairwise comparisons.

The highest percentage of microhardness loss was observed at 30 μm in FG (35.7%) and in CO (51.9%) (p< 0.05).

This study suggests that laser irradiation, with or without fluoride application, is associated with reduced microhardness loss in root dentin. Key words:Dentin, Fluoride, Hardness Tests, Laser, Root caries.