Effect of Nd: YAG laser on the treatment of intraradicular dentin prior obturation with calcium silicate-based sealer.

Abstract

To evaluate the effect of Nd:YAG laser irradiation on intraradicular dentin prior to obturation with calcium silicate-based and epoxy resin-based sealers, focusing on push-out bond strength, failure pattern using a stereomicroscope, adhesive interface quality via confocal laser scanning microscopy (CLSM), chemical composition using Raman spectroscopy, and dentin surface morphological alterations through scanning electron microscopy (SEM). Forty-six teeth were sectioned to standardize root length (16 mm) and prepared using a reciprocating R50 instrument. Specimens were randomly divided into control (no treatment) and Nd: YAG laser (1,064 nm) groups, with laser irradiation performed at 1.5 W, 25 Hz, for 20 s using a 400 μm fiber in a helical motion (1.5 mm/s). Twenty specimens per group were obturated using the single-cone technique with R50 gutta-percha and further subdivided by sealer: AH Plus (n = 10) and Bio-C Sealer (n = 10), with and without laser treatment. Three non-obturated specimens per group underwent Raman spectroscopy and SEM analysis of intracanal dentin. After 30 days at 37 °C, obturated samples were sectioned into slices (nine per specimen). The first two slices per third underwent push-out bond strength testing and failure analysis, while the third was examined via CLSM for adhesive interface quality. Bond strength was analyzed using three-way ANOVA, chemical composition by two-way ANOVA, failure patterns by chi-square, and interface adaptation by Kruskal-Wallis with post-hoc tests (p < 0.05). In laser groups, Bio-C Sealer showed higher bond strength in the cervical third (p = 0.011), whereas AH Plus maintained superior values in the middle and apical thirds (p < 0.001). The laser group obturated with Bio-C Sealer demonstrated adhesive interface adaptation comparable to the control group obturated with AH Plus (p = 1.000) and superior to the control group obturated with Bio-C Sealer (p = 0.037). Laser groups exhibited more mixed failures, while control groups showed a higher prevalence of adhesive failures (p = 0.045). Laser irradiation resulted in lower organic content intensity in the cervical third (p = 0.002) and an increased inorganic/organic ratio (p < 0.001). Additionally, it induced fusion and obliteration of dentinal tubules in the cervical third, whereas alternating areas of fused dentin and exposed tubules were observed in the middle and apical thirds. The Nd:YAG laser treatment of intraradicular dentin prior obturation positively influenced the obturation process when associated with Bio-C Sealer, particularly in the cervical third. Therefore, Nd:YAG laser may be a promising approach to enhance bond strength and improve the adhesive interface quality of obturations performed with calcium silicate-based sealers.