Efeito do plasma de argônio na resistência de união de duas técnicas adesivas em substratos de esmalte e dentina humanos hígidos e desmineralizados

Abstract

The aim of this study was to determine the effect of argon plasma on the bond strength of two adhesive techniques on healthy and demineralized human enamel and dentin substrates. The blocks were selected from the initial surface hardness. For demineralization of half of the specimens, a microbiological biofilm model with periodic nutrient exchange and presence of sucrose were used using Streptococcus mutans UA159. Biofilms were incubated at 37°C and 5% of CO2 for 5 days. Etch-and-rinse and self-etching techniques were tested using Single Bond Universal® adhesive and Z100® resin according to the manufacturer's instructions. From the crowns, beans sticks of approximately 0.9 mm² were obtained for the microtensile bond‐strength test, while the half-crowns were kept intact for shear technique. Healthy or demineralized blocks were randomly divided into three groups (n = 5) and were submitted to the following treatments: untreated control, argon plasma, argon gas and untreated control. The sample of half-crowns and crowns were divided into six groups (n = 5), according to the two adhesive techniques and submitted to the same treatments. Surface microhardness, scanning electron microscopy, Micro-Raman spectroscopy and contact angle analyzes were performed on the blocks. Enamel half-crowns were evaluated by the shear bond strenght test while dentin crowns were evaluated by the microtensile bond‐strength test. The data normality was evaluated using Kolmogorov-Smirnov test, with significance level of 5%. Results were submitted to ANOVA analysis of one, two or three factors. The post-test used was the Bonferroni test. The treatment with plasma did not alter the microhardness as well as the surface morphology of healthy enamel, healthy dentin, and demineralized enamel. However, there was a greater opening of dentin tubules in the demineralized dentin of the plasma and argon groups. Changes in Micro-Raman technique were observed only for carbonate in the structure of demineralized enamel treated with the argon gas. The results of the contact angle demonstrated that the wettability of demineralized dentin substrates was improved by the treatment with plasma and with argon gas. In healthy and demineralized enamel, the treatments did not alter the contact angle. The use of plasma did not increase the adhesion to the healthy or biofilm-demineralized enamel, although demineralized teeth show less shear strength than the healthy teeth (p <0.05). Etch-and-rinse technique had a high average (7,857) than self-etching technique. Regarding dentin, the treatments had no effect on micro-traction (p>0.05) and Etch-and-rinse technique had the highest average (27,428). Under the tested conditions, the use of argon plasma did not alter the properties of healthy substrates of enamel and dentin, improving wettability of biofilm-demineralized dentin.