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 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 (1Χ1mm), created on six defect-free incisors, were characterized by the FT-Raman microscopy (Bruker, 1024 nm) before and after Er:YAG (Fidelis^® Solvenia) laser treatment with 5.1 J/cm²-5s-2Hz. To assess the statistical significance of laser effects Raman peaks assigned to v1 phosphate, type-A/B carbonates, and organic matrix were evaluated with paired-samples t-tests. Results: The intensity of type B carbonate (standardized by v1 phosphate) decreased significantly from 0.117±0.024 to 0.106±0.019 (p=0.029), whereas the intensity of carbonate A (standardized by v1 phosphate) remains constant (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 v1 phosphate on lased surfaces appeared to be similar to that of their non-lased counterparts (p=0.477). Conclusions: Laser treatment may provide caries-preventive effect on enamel through reduction of carbonate and modification of organic matters. This project was supported by Singapore BMRC grant R222-000-015-305.