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.