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

Abstract 

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 (1mm×1mm), created on six defect-free primary incisors, were characterized by FT-Raman microscopy (1024nm) before and after Er:YAG laser treatment (Fidelis^®) with 5.1J/cm²–2Hz–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 2940cm⁻¹ and in the ranges of 1200–1600cm⁻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.

Keywords: Er:YAG laser, Raman spectroscopy, Human enamel, Carbonate, Organic matters