Aplicação de polifenois na dentina humana : estudo in vitro da morfologia interfacial e da resistência de união

Abstract

(Artigo 1 Effect of a collagen stabilizing acid conditioner on adhesion to enamel and dentin) The aim was to evaluate the effect of different concentrations of phosphoric acid with grape seed extract (GSE) on the enamel acid etching, on the immediate bond strength to enamel, and on the bond strength to dentin after 12 months storage. Three different phosphoric acid formulations with GSE were obtained: GSE5 - 5% phosphoric acid + 20% ethanol + 2% GSE; GSE10 -10% phosphoric acid + 20% ethanol + 2% GSE; GSE20 - 20% phosphoric acid + 20% ethanol + 2% GSE; GC (control) - 37% phosphoric acid. The enamel and dentin surfaces of third molars, extracted for therapeutic reasons, were etched with 37% phosphoric acid for 15 s, and with the modified acids for 30 s. The acid was rinsed, followed by application of Adper Scotchbond Multipurpose adhesive system, and a block of composite resin was built. In enamel, the etching pattern was evaluated by scanning electron microscopy (SEM) and the bond strength was evaluated by conventional tensile test. In dentin, the microtensile bond strength (μTBS) was evaluated after 24 h and 1 year of storage. SEM images showed that GSE5 caused a more superficial enamel etching. According to ANOVA and Tukey’s test, enamel bond strength did not differ significantly between GC (49.00 MPa), GSE5 (42.78 MPa), GSE10 (51.55 MPa) and GSE 20 (36.18 MPa) (p> 0.05).According to two-way ANOVA and Tukey’s test, the interaction of factors (treatment x storage time) was significant (p=0.0001). At the 24 h of storage, GC (28.43 MPa) obtained the highest μTBS, and did not differ significantly from GSE20 (24.11 MPa). GC and GSE20 were significantly higher to the others (p<0.05).The GSE10 (17.53 MPa) and GSE5 (16.75 MPa) did not differ significantly from each other. At the 12 months of storage, there was no significant difference in μTBS between GC (17.71 MPa), GSE5 (20.97 MPa), GSE10 (17.59 MPa) and GSE20 (18.52 MPa). Only GSE5 and GSE10 did not significantly decrease μTBS after 12 months of storage. It was concluded that GSE5 caused a more superficial enamel etching pattern in relation to the acid concentrations at 37%, 20% and 10%. However, there was no significant difference in the bond strength to enamel among the four concentrations. GSE5 and GSE10 promoted stability of the bond strength to dentin after 12 months of storage. (Artigo 2 Effect of phosphoric acid with polyphenols on dentin collagen : Atomic force microscopy study) Objective: The aim was of this study to evaluate the effect of different concentrations of phosphoric acid with grape seed extract (GSE) on the structure of the collagen fibrils of dentin. Materials and methods: Samples (0.3 mm thickness and 8 mm diameter) of the middle third of the coronal dentin of sound human molars were obtained. Half of the dentin of each tooth was etched with phosphoric acid (5%, 10%, or 20%) for 30 s, and the other half was etched with its corresponding phosphoric acid with 2% GSE for 30 s. The dentin of each sample was observed using an Atomic Force Microscope (AFM). Results: AFM images showed that phosphoric acid at concentrations of 5%, 10% and 20% demineralized the dentin and exposed the collagen fibrils and their pattern of periodicity. Phosphoric acid at each concentration with 2% GSE changed the collagen fibril periodicity, and the collagen fibrils formed globular structures. This change was more significant in dentin treated with 5% phosphoric acid and less significant with 20% phosphoric acid. Conclusions: The use of 5% phosphoric acid with 2% GSE produced denser collagenous globular structures. This conformational change in the collagen can make it more mechanically and enzymatically resistant.