Effects of the CO₂ laser combined with fluoridated toothpaste on human dental enamel demineralization

This in vitro pilot study investigated the CO₂ laser effects on demineralization inhibition in sound human dental enamel. Thirty six human enamel specimens were used and randomly assigned to 6 groups, as follows: I) Control; II) 1W; III) 2W; IV) 3W; V) 4W; VI) 5W. Group I one was kept as control and others were irradiated using a pulsed CO₂ laser (λ=10.6 μm) with low crescent potencies. Fourier Transform Raman Spectroscopy was used to study the surface composition of specimens after irradiation. One specimen from each group was analyzed by Scanning Electron Microscopy and the remaining ones were submitted to an 8-day pH cycling model with use of fluoridated toothpaste twice a day. After pH-cycling, the cross-sectional microhardness was performed for mineral loss (ΔZ) quantification. The data were analyzed by ANOVA and Tuckey test (α=0.05). No changes were found either in SEM photomicrographies or RAMAN Spectra of the specimens in all groups. The AZ values (n=5; mean±SD) for I-VI groups were: 1741.6±725.3a; 1782.7±639.0a; 1427.2±237.0a; 1780.6±552.4a; 1385.2±602.2a; 943.1±228.1a respectively. The highest percentage of caries inhibition was found in group VI (45.8%); however the differences between AZ of the groups were not statistically significant. The use of CO₂ laser with low fluencies did not prevent more caries development than the use of fluoridated toothpaste, even though group VI had present good results in caries inhibition. Energy densities higher than 0.0125 J/cm² should be used to promote chemical or morphological changes on enamel surface, which are able of inhibiting mineral.