Enamel erosion prevention and mechanism: effect of 10.6-μm wavelength CO2 laser low power density irradiation studied by X-ray fluorescence and infrared spectroscopy and scanning electron microscopy

This study assessed the effects of carbon dioxide (CO2) laser (λ = 10.6 μm, 5 W, 70 J/cm2) irradiation alone and after treatment with neutral fluoride gel on enamel and their efficacy in preventing enamel erosion compared to untreated and fluoride gel-treated enamel. Enamel surfaces of the bovine incisor (n = 7/group) were treated with artificial saliva (S, negative control), neutral fluoride (NF, positive control), CO2 laser irradiation (L), and NF + laser (NF + L). Samples were acid demineralized (soft drink, pH ~ 3.2, 10 min), remineralized (saliva, 37 °C, 1 h), and analyzed using micro-energy-dispersive X-ray fluorescence spectrometry (μ-EDXRF), attenuated total reflectance–Fourier-transform infrared (ATR-FTIR) spectroscopy, and scanning electron microscopy (SEM). Results suggest that NF gives the best protection against erosion, followed by NF + L and L. μ- EDXRF showed that changes due to laser treatment in L and NF + L were uneven. SEM images showed morphological changes in L and NF + L such as craters, fissures, and roughness in some regions, again indicating the unevenness of laser-induced enamel changes. ATR-FTIR mean spectra intensity levels and principal component analysis also indicate higher efficacy of fluoride over laser treatments and unevenness of laser treatments. Overall, it can be concluded that CO2 laser parameters need to be further investigated to promote adequate protection with minimum surface changes.