Combined FT-Raman and SEM studies of the effects of Er:YAG laser irradiation on dentin.

OBJECTIVE This study evaluated the molecular and morphological changes on dentin elements after Er:YAG laser irradiation. BACKGROUND DATA Spectroscopy studies reporting the effects of Er:YAG laser irradiation as an alternative to acid etching are needed to better understand the laser's effects. METHODS The occlusal one-third of the crown of six human third molars was removed. The dentin surface was schematically divided into areas corresponding to four surface treatment groups: control (group C): 37% phosphoric acid etching; group I: Er:YAG laser 80 mJ; group II: Er:YAG laser 120 mJ; and group III: Er:YAG laser 180 mJ. The analysis was performed by scanning electron microscopy (SEM) and Fourier transform Raman spectroscopy (FT-Raman) before and after the treatments. Raman data were submitted to ANOVA and Bonferroni tests. RESULTS The SEM photomicrographs revealed open dentin tubules in the control group. The molars from groups I, II, and III showed partially open dentin tubules. SEM images showed that the laser-irradiated dentin surface was not favorable to the diffusion of monomers. A significant reduction of the spectra relative intensity was observed in group III specimens. CONCLUSIONS Er:YAG laser irradiation with 180 mJ could produce chemical changes in proteins, phosphate, and carbonate in dentin.