Botulinum toxin promotes orofacial antinociception by modulating TRPV1 and NMDA receptors in adult zebrafish.

The aim of the study was to evaluate the possible involvement of transient receptor potential (TRP) channels, Acid-sensing ion channels (ASIC) and N-Methyl-D-aspartate receptor (NMDAR) in the orofacial antinociceptive behaviour effect of botulinum toxin type A (BoNT/A) in adult zebrafish. Initially, the open field test was performed to evaluate the effect of BoNT/A on the locomotor activity of zebrafish. Subsequently, the animals were pretreated with BoNT/A (0.05U, 0.1U or 0.5U/masseter) and acute orofacial nociception was induced by cinnamaldehyde, capsaicin, menthol, acid saline or glutamate applied to the lip or masseter muscle. In another group of experiments, animals were pre-treated with capsazepine (TRPV1 antagonist) or ketamine (NMDAR antagonist) to investigate the mechanism of antinociception. The possible involvement of central C-fibre afferents was also investigated using capsaicin desensitized animals. A molecular docking study was performed to observe the in silico interaction of BoNT/A with TRPV1 and NMDA channels. Pretreatment with BoNT/A reduced the nociceptive behaviour induced by capsaicin and glutamate. Antinociception was effectively inhibited by capsazepine and ketamine, as well as by capsaicin-induced desensitization. Consistent with these in vivo findings, the molecular docking study indicated that BoNT/A can interact with TRPV1 and NMDAR. The results indicate the involvement of TRP and NMDAR mechanisms in the orofacial antinociceptive behaviour effect of BoNT/A. The results also confirm the pharmacological relevance of BoNT/A as an inhibitor of orofacial nociception behaviour.

Cementation of ceramics and indirect composite resin to enamel and dentin using different resin-based cements ? Shear bond strength / Cimentação de cerâmica e resina composta indireta ao esmalte à dentina usando diferentes cimentos resinosos - resistência ao cisalhamento

Objective: To evaluate the shear bond strength of three different resin cements: self-etching (P), etch-and-rinse (R) and self-adhesive (U), to enamel and dentin using two types of restorative materials. Methods: One hundred twenty bovine incisors had the buccal surface ground to obtain a flat and smooth surface of approximately 25 mm2. Half of the specimens had the enamel exposed (E), and the other half had the dentin exposed (D). An ad-hesive tape with a 3 mm-diameter orifice delimited the bonding area. Sixty 3 x 3 mm lithium disilicate glass-ceramic cylinders (C) and 60 indirect composite resin cylinders (R) were cemented to enamel or dentin using three types of resin cements, resulting in 12 experimental groups represented by symbols allusive to treatment protocols: PEC; PER; PDC; PDR; REC; RER; RDC; RDR; UEC; UER; UDC; and UDR. Shear bond strength test was performed with a crosshead speed of 0.5 mm/min. The data were subjected to ANOVA and Tukey?s test with a significance level of 5%. Results (MPa ± DP): the highest mean value obtained, REC group (17.46 ± 3.29), differed significantly from others, except for the PEC group (14.60 ± 5.88). Among the groups with lower mean values, there was a predominance of those where the indirect resin was used regardless the substrate and type of resin cement, and the UDR group (1.03 ± 1.03) was statistically different from the others. Conclusion: In this study, all three experimental variables tested influenced the shear bond strength of tooth-cement-restoration interfaces.