Effect of sodium fluoride and stannous chloride associated with Nd:YAG laser irradiation on the progression of enamel erosion

This study evaluated the progression of enamel erosion after treatment with gels containing sodium fluoride (NaF; 9047 ppm F) and stannous chloride (SnCl₂; 3000 ppm Sn), associated or not with Nd:YAG laser irradiation. Sixty enamel specimens were prepared from bovine incisors and protected by a tape, leaving an exposed surface area of 4 × 1 mm. The specimens were immersed in 1 % citric acid (pH = 2.3) for 10 min to create an initial erosion lesion. After, they were randomly divided into six groups: (C) control: gel without active ingredient; (F): NaF gel; (F + Sn): NaF + SnCl₂ gel; (laser): Nd:YAG laser irradiation (0.5 W; 50 mJ; ∼41.66 J/cm²; 10 Hz; 40 s); (F + laser): NaF gel + Nd:YAG; (F + Sn + laser): NaF + SnCl₂ gel + Nd:YAG. All gels had pH = 4.5 and were applied for 1 min. Laser irradiation was performed after gel application. The specimens were then submitted to a 5-day erosion-remineralization cycling model using 1 % citric acid (pH = 2.3), six times per day. Enamel surface loss (SL) was analyzed by optical profilometry in the end of the cycling (in μm). Data were analyzed by one-way ANOVA and Holm-Sidak tests (alpha = 0.05). The control and the laser groups presented the highest enamel loss (means ± SD = 53.52 ± 3.65 and 53.30 ± 2.73, respectively), followed by F + Sn (44.76 ± 2.83). The groups F (36.76 ± 2.28), F + laser (36.25 ± 3.59), and F + Sn + laser (39.83 ± 4.62) showed the lowest enamel loss, with no significant difference among them (p > 0.05). In conclusion, NaF by itself or associated with SnCl₂ and Nd:YAG laser was able to reduce enamel erosion progression. Nd:YAG laser alone did not show a protective effect.