Diferença no padrão de desmineralização da dentina usando diferentes protocolos de aplicação de ácido fosfórico

Abstract

The aim of this study was to analyze the differences in the demineralization pattern of the dentin substrate, observing morphological differences and the effect of the etching time when using different commercial brands of phosphoric acid, as well as its influence on dentin adhesion. 200 human molars free of dental caries were selected, divided according to the tests to be performed. The acids used were: UD-Ultra-etch [Ultradent]; 3M-Scotchbond ™ Universal Etchant [3M], DP-Dental Gel Conditioner [Dentsply-Sirona] and IV-Total Etch [Ivoclar Vivadent] at phosphoric acid application times (3 and 15 seconds) for the demineralization depth test by lateral view through Scanning Electron Microscopy (SEM). For the tests: occlusal assessment by tubular density, topography assessment by 3D roughness using optical profileometry, chemical mapping using micro-Raman spectroscopy, analysis of Ca concentration using energy dispersion spectroscopy (EDS), were used conditioning times 0, 3 and 15 seconds. In microtensile bond strength tests (μTBS) and Nanoleakage (NL) tests, the adhesive and resin used were Peak Universal Bond [Ultradent] and Forma Zirconia Nano-Hybrid Composite [Ultradent], respectively. The pH measurement and the buffering capacity of the acids were also carried out through solutions with deionized water in the proportion 1: 2 (by weight). Two-way ANOVA and post-hoc Tukey test (ɑ = 0.05) were applied for the depth of demineralization and tubular density, for the other quantitative analyzes we used One-way ANOVA. The results show that for all acids, a lower depth of demineralization was found, etching for less time. For the tests of occlusal evaluation by tubular density, roughness, and chemical mapping, the data show a lower rate of demineralization in 3 s for all groups, except for UD acid, which presented a similar behavior with 3 and 15 s. In an analysis between acids, it was seen that UD and 3M showed a less aggressive potential, positively impacting the values of μTBS and NL; however, only UD acid did not show any difference in the studied times (3 and 15 s). No difference was found between acids for the amount of Ca; however, there was a difference for all groups between times 0, 3 and 15 s. In evaluating the pH of the acid solution, a lower value for IV acid was found.It is concluded that UD acid promotes less accentuated demineralization, avoiding an overexposure of collagen fibers. Etched dentin for 3 seconds can lead to significant changes in its structure and be sufficient to allow the penetration of adhesive monomers into the demineralized collagen web.