Effect of Nd:YAG and CO₂ Laser Irradiation on Prevention of Enamel Demineralization in Orthodontics: In Vitro Study

The aim of this study was to investigate Nd:YAG and CO₂ laser effects in the prevention of demineralization in deeper layers of enamel via successive acid challenge cycles.

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.

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/cm², 10 Hz, 110 μs, contact mode); G3-Nd:YAG laser irradiation associated with AFP; G4-CO₂ laser irradiation (0.5 W, 28.6 J/cm², 50 Hz, 5 μs, and 10 mm focal distance); and G5-CO₂ 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 (α = 5%).

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 CO₂ laser groups had significantly lower mineral losses than those observed in all other groups after successive acid challenge cycles.

Only the CO₂ laser (10.6 μm) irradiation prevents enamel demineralization around the orthodontic brackets even after exposure to successive acid challenges. The CO₂ laser at 10.6 μm showed a deeper effect in enamel regarding caries prevention.