Evaluation of an experimental bioglass on surface loss and tubular occlusion of dentin, and its association with photobiomodulation therapy in human pulp cell differentiation

Dentin hypersensitivity (DH) is a painful oral condition that negatively affects the quality of life of individuals. However, there is still no treatment considered the gold standard to mitigate the acute pain generated by this condition. Therefore, the aims of this study were: 1. To verify the effects of an experimental bioglass on dentin permeability (DP, by hydraulic conductance) and dentin surface loss (dSL, by optical profilometry); 2. To analyze the effects of the association of bioglass with photobiomodulation therapy in the functional differentiation of pulp cells, indicating a potential for tertiary dentin formation and biological occlusion of dentinal tubules. For the first phase of the study, 48 coronal dentin discs (1 mm thick, n=12) were used for DP and 48 root dentin slabs (3 mm × 3 mm, n=12) for dSL, which were evaluated at 3 times: post-EDTA (5 min in 17% EDTA solution); post-treatment (C: distilled water; BG: experimental bioglass paste; NP: Nupro prophylaxis paste; CXT: Clinpro XT varnish); and post-cycling (0.3% citric acid solution for 5 min, followed by 60 min immersion in human saliva, 4 ×/day, 5 days. Brushing was performed 2 ×/day for 15 s, with 1.5 N and a standard fluoride toothpaste slurry - 2 min total exposure). Scanning electron microscopy images (SEM, n=3) were obtained post-treatment and post-cycling for qualitative analysis. Additional images of the bioactive glass powder and analysis by energy dispersive spectroscopy (EDS) were performed to characterize the particle. In the second phase, the same treatments were tested, associated or not with the photobiomodulation therapy [PBM - indium-gallium-aluminum phosphide diode laser, InGAlP, (660 nm, 0.028 cm2, 20 mW, 0.71 W/cm2, 5 J/cm2) 7 s, continuous mode, punctual and in contact], regarding the functional differentiation of human dental pulp cells, using the Alizarin red assay. Data were subjected to appropriate statistical analysis, considering =0.05. For DP and dSL, groups did not differ significantly after EDTA (p>0.05). Post-treatment, all groups had DP lower than C (p<0.05), without significantly differences between them. For dSL, C, BG and NP did not differ significantly, presenting lower values than CXT (p<0.05). After cycling, C remained with the highest DP (p<0.05). CXT had the lowest DP, not differing from NP (p=0.86) which did not differ from BG (p=0.193). For C and BG, the PD was higher post-cycling than post-treatment (p<0.05). For NP and CXT, these experimental times did not differ (p>0.05). Post-cycling, groups C, BG and NP did not differ significantly in terms of dSL, being greater than CXT (p<0.05). SEM images showed occlusion of dentinal tubules through the formation of a layer over dentin specimens after application of treatments, except for the control group. After cycling, a partial removal of this layer was observed. Regarding the formation of mineralized nodules, within 7 days, there was no statistical difference between the experimental groups (p=0.397). After 14 days, the BG group showed greater mineralization potential, differing statistically from the negative control -MEM (p<0.05), but not from the other groups. After 21 days, the BG, Differentiation Medium (positive control), BG + PBM and CXT groups showed higher mineralization potential, with no statistically significant differences between them. It is concluded that BG was able to reduce dentin permeability after application, with a reduced effect after cycling, but it did not protect the dentin against erosive tooth wear. In addition, BG showed a potential for the formation of mineralized nodules after 14 and 21 days, however PBM did not improve its performance. (AU)