Preventive Effect of Fluoride and LED/Laser Irradiation on Dentin Erosion

Due to the increase of non-carious cervical lesions by erosion new preventive strategies have been developed to obtain a more acid-resistant dentin substrate. Objectives: This in vitro study aimed to evaluate the effect of low intensity diode lasers (l= 660 or 808 nm; 100 J.cm^-2) and a light emitting diode –LED(l=430-480 nm; 1200 mW/cm²) associated with fluoride on the inhibition of dentin erosion. Methods: Human root dentin slabs were randomly assigned to eight groups (n=10), as follows: G1- control, G2- Fluoride (5 min), G3- LED, G4- laser (660 nm), G5- laser (808 nm), G6- Fluoride + LED, G7- Fluoride + laser (660 nm) and G8- Fluoride + laser (808 nm). After being submitted to a 2-h-acquired pellicle formation, the slabs were treated according to the groups (1x/day) and subsequently exposed to cyclic erosive challenges (0.01 M HCl for 60 s, 4x/day), during 3 days. Surface changes were determined by microhardness and profilometry analyses. Additionally, temperature was evaluated during dentin irradiation by K-type thermocouple wire. Results: Kruskal-Wallis and Student-Newman-Keuls tests were used to compare the percentage of surface hardness loss (%SHL) and ANOVA to assay tissue wear. For all irradiated groups, temperature changes were below 1.6°C and not statistically significant different (p<0.05). Means (±SD) for %SHL and surface wear (µm) were respectively: G1 (31.69±8.68; 1.28±1.06), G2 (6.67±23.63; 1.11±0.77), G3 (5.60±10.51; 1.06±0.66), G4 (3.67±20.80; 0.90±0.57), G5 (11.44±16.43; 1.20±0.55), G6 (-0.45±27.42; 0.76±0.52), G7 (7.97±18.95; 0.84±0.53) and G8 (5.68±8.44; 0.84±0.54). Treated groups did not present evidence of erosion reduction for wear rates (p=0.27), however, for %SHL, a statistically significant difference was found among treated and control groups. Conclusion: All treatments were able to reduce loss of hardness of dentin submitted to a slight erosive challenge. However, no synergic effect was found when fluoride was associated with light irradiation.