Randomized in situ study on the efficacy of CO(2) laser irradiation in increasing enamel erosion resistance.

OBJECTIVES: The aim of this double-blind, randomized in situ study was to evaluate the erosion-preventive effect of a specific set of CO(2) laser parameters, associated or not with fluoride. METHODS: Two hundred forty bovine enamel blocks were prepared for individual palatal appliances (n = 6 samples/appliance). The study had four phases of 5 days each, with ten volunteers and the following treatments: CO(2) laser irradiation (L), fluoride treatment (F), combined fluoride and laser treatment (FL), and no treatment, control (C). Laser irradiation was performed at 0.3 J/cm(2) (5 mus/226 Hz/10.6 mum) and the fluoride gel contained AmF/NaF (12'500 ppm F(-)/pH = 4.8-6). For erosive demineralization, the appliances were immersed extra-orally in citric acid (0.05 M/20 min/pH = 2.3) twice daily. Analysis of enamel surface loss was done using a 3D-laser profilometer on 3 days. Additionally, fluoride uptake was quantified and scanning electron microscopies were done. Data were analyzed with repeated measures ANOVA and post hoc pairwise comparisons (alpha = 0.05). RESULTS: At all analyzing days, both laser groups caused the lowest means of enamel loss, which were also statistically significant lower than C (p < 0.05). At day 5, FL means +/- SD (33.6 +/- 12.6 mum) were even significantly lower than all other groups (C 67.8 +/- 15.4 mum; F 57.5 +/- 20.3 mum; L 46.8 +/- 14.5 mum). Significantly increased enamel fluoride uptake was observed for both fluoride-containing groups (p < 0.05) at day 1. CONCLUSION: Compared to the control, the CO(2) laser irradiation with a specific set of laser parameters (0.3 J/cm(2)/5 mus/226 Hz) either alone or in combination with a fluoride gel (AmF/NaF) could significantly decrease enamel erosive loss up to 5 days in situ. CLINICAL RELEVANCE: Combined CO(2) laser-fluoride treatment has a significant anti-erosive effect.