Laser-induced compositional changes on enamel: A FT-Raman study

Preventive effects of lasers on enamel caries have been documented in the past few decades. However, its specific mechanism remains uncertain. Objectives To evaluate the laser-induced change of enamel compositions, including carbonate and organic matters using Fourier-transform Raman spectroscopy (FT-Raman). Methods Twelve windows (1 mm × 1 mm), created on six defect-free primary incisors, were characterized by FT-Raman microscopy (1024 nm) before and after Er:YAG laser treatment (Fidelis®) with 5.1 J/cm2–2 Hz–5s. To assess the statistical significance of laser effects, Raman peaks assigned to ν1 phosphate, type-A/B carbonates, and organic matters were evaluated with the paired-samples t-test. Results The standardized intensity of type B carbonate decreased significantly from 0.117 to 0.106 (p = 0.029), whereas the standardized intensity of carbonate A remained unchanged (p = 0.467). Related to organic matters, the standardized intensity of peaks at 2940 cm−1 and in the ranges of 1200–1600 cm−1 decreased significantly, with p = 0.005 and p < 0.001, respectively. Revealing enamel crystallinity, the bandwidth of ν1 phosphate on lased surfaces appeared to be unaltered after laser treatment (p = 0.477). Conclusions Laser treatment may provide caries-preventive effect on enamel through reduction of carbonate and modification of organic matters.