Effect of Nd:YAG and CO(2) Laser Irradiation on Prevention of Enamel Demineralization in Orthodontics: In Vitro Study.

OBJECTIVE: The aim of this study was to investigate Nd:YAG and CO(2) laser effects in the prevention of demineralization in deeper layers of enamel via successive acid challenge cycles. BACKGROUND DATA: Lasers are promising in the prevention of enamel demineralization around the orthodontic brackets; however, there are very few studies that evaluate if the effects of treatment could be extended after successive acid challenge cycles due to permanent enamel structural alterations. MATERIALS AND METHODS: Human enamel samples were divided into five groups (n = 12): G1-application of 1.23% acidulated fluoride phosphate gel (AFP, control); G2-Nd:YAG laser irradiation (0.6 W, 84.9 J/cm(2), 10 Hz, 110 mus, contact mode); G3-Nd:YAG laser irradiation associated with AFP; G4-CO(2) laser irradiation (0.5 W, 28.6 J/cm(2), 50 Hz, 5 mus, and 10 mm focal distance); and G5-CO(2) laser irradiation associated with AFP. The samples were submitted to successive acid challenge cycles. Quantitative light-induced fluorescence and scanning electron microscopy were used to assess enamel demineralization. The data were statistically compared (alpha = 5%). RESULTS: G1: 50.87 +/- 4.57; G2: 47.72 +/- 2.87; G3: 50.96 +/- 4.01; G4: 28.21 +/- 2.19; and G5: 30.13 +/- 6.38. The CO(2) laser groups had significantly lower mineral losses than those observed in all other groups after successive acid challenge cycles. CONCLUSIONS: Only the CO(2) laser (10.6 mum) irradiation prevents enamel demineralization around the orthodontic brackets even after exposure to successive acid challenges. The CO(2) laser at 10.6 mum showed a deeper effect in enamel regarding caries prevention.