Low-level gallium-aluminum-arsenide (GaAlAs) diode laser irradiation (λ 830 nm) associated with and without fluoridated gel in the prevention of enamel erosion

Purpose This in vitro study evaluated the effect of a low-level gallium-aluminum-arsenide (GaAlAs) diode laser irradiation against erosion in bovine enamel without and combined with fluoride (F), as well as compared the effect of the F treatment alone. Methods Eight-four enamel samples were used for 8 groups: negative control (artificial saliva, S); positive control (neutral fluoride gel, F); diode laser (222 J/cm 2 , L1); diode laser (444 J/cm 2 , L2); F_L1; F_L2; L1_F; L2_F. Fluoride gel was applied only once before or after irradiation. Laser treatment occurred with an 830-nm diode laser (continuous, beam diameter 0.028 cm 2 , power 100 mW, power density 3.57 W/cm 2 ). The irradiation was conducted one time (L1, energy 6.2 J, 62 s, energy density 222 J/cm 2 ) or two times (L2, energy 12.4 J, 124 s, energy density 444 J/cm 2 ). The specimens were submitted to erosive challenge using orange juice. Surface compositional changes by micro energy-dispersive X-ray fluorescence spectrometry (μ-EDXRF), surface roughness, and surface morphology by scanning electron microscopy (SEM) were evaluated after cycling. Results The laser energy density and the fluoride application (before or after laser) affected the mineral content. Treatments with the association laser/fluoride resulted in lower roughness values (Ra, μm) than in the negative control ( p