Chemical and morphological analysis of dentin collagen degradation after Nd:YAG laser irradiation

Abstract

Objective: The present study aimed to evaluate root dentin collagen degradation after Nd:YAG laser irradiation by using polarized light microscopy and spectroscopy analysis. Background: Quantification of collagen degradation is an important parameter to evaluate dentin caries progression. Methods: Discs (2 mm in thickness × 6 mm in diameter) of bovine root dentin were obtained and submitted to demineralization by artificial caries lesion formation. The specimens were randomly divided into two groups according to the following treatments: C—control (no treatment) and L—Nd:YAG laser irradiation (1064 nm; 60 mJ; 10 Hz; 48 J/cm2; non-contact; 30 s). After the treatment, the specimens were exposed to the collagenase enzyme challenge for 5 days. Chemical analysis of the dentin surface was performed by FT-IR spectroscopy. Specimens were sectioned longitudinally to prepare slides for polarized light microscopy evaluation to provide the measure of depth of the degraded collagen in the demineralized area. Data were submitted to the Student’s t-test (p < 0.05). Results: According to the t-Student test (t-value = 5.089), it was observed that the Nd:YAG laser showed statistically significant differences when compared to the control group (p < 0.001). Chemical differences in dentin were observed through the reduction of amide, carbonate, and phosphate groups present in the collagen matrix after laser irradiation. Conclusions: Nd:YAG laser promoted chemical and morphological changes in the surface of the root dentin, showing effectiveness in reducing collagen degradation.