AVALIAÇÃO IN VITRO DAS PROPRIEDADES ÓPTICAS E COMPORTAMENTO MECÂNICO DA TÉCNICA DE INFILTRAÇÃO DE ADESIVO A BASE DE S-PRG EM ESMALTE COM HIPOMINERALIZAÇÃO INDUZIDA

Abstract

Despite the increased prevalence of hypomineralized teeth, there is still no scientific evidence defining microinvasive treatment for mild hypomineralized lesions in anterior teeth. The aim of this study was to evaluate in vitro the optical properties (brightness and color alteration) and mechanical properties (surface microhardness and nanoinfiltration) of resin infiltrant and adhesive with bioactive glass particles (Giomer) applied to hypomineralized dental enamel. Eighteen enamel blocks (6x6x2mm) were obtained from bovine incisors and polished with a sandpaper sequence for initial color evaluation using the Easyshade V spectrophotometer (Vita Zahnfabrik, Bad Sackingen, Germany) and superficial Knoop microhardness (HK) using a microhardness tester (Future-Tech Corporation, Tokyo, Japan). After the initial measurements, the samples were randomized and allocated into groups (n=9/group): EH.Icon - application of resin infiltrant Icon (DMG, Hamburg, Germany) and EH.S-PRG - application of FLBond II dentin adhesive with S-PRG technology (Shofu Inc., Kyoto, Japan). A dental enamel hypomineralization protocol was followed, and using energydispersive spectroscopy (EDS), a decrease in Ca and P concentrations and an increase in organic content were verified. The samples were stored in artificial saliva for 24 hours, and color analysis was performed followed by the application of resin systems in the experimental groups. After the treatments, new color analyses were immediately conducted and 30 days post-treatment. After 30 days of storage in distilled water, the samples were vertically sectioned, with one half used for transverse microhardness measurement (25, 50, and 90 µm) and the other half used for nanoinfiltration reading through Scanning Electron Microscope (SEM) visualization of silver nitrate infiltrated between the resin system and enamel. Two-way ANOVA and Tukey's post hoc tests (α=5%) were employed. When evaluating optical properties, a brightness alteration was observed in enamel with induced hypomineralization immediately after applying the bioactive adhesive, and both materials caused a clinically visible color change immediately and after 30 days of treatment. Regarding mechanical behavior, the infiltrant promoted an increase in subsurface enamel microhardness, but the bioactive adhesive showed indications that it may have higher microhardness values closer to the subsurface, gradually decreasing with depth. Both materials showed low nanoinfiltration rates after 30 days of evaluation (p < 0.05). In conclusion, the EH.S-PRG group showed brightness alteration in enamel with induced hypomineralization immediately after treatment, and both tested materials showed visible color change. Additionally, the EH.Icon group exhibited an increase in subsurface enamel microhardness after 30 days, with low nanoinfiltration rates and no difference from the group treated with bioactive adhesive.