Resina odontológica para impressão 3D com óxido de grafeno fluorado e fluoreto de sódio : propriedades térmicas, mecânicas e potencial de liberação de íons fluoreto

Abstract

The present study aimed to characterize composites and nanocomposites based on a photocurable liquid acrylic resin for 3D printing (RES), intended for the fabrication of occlusal splints, which are inert devices used in the management of bruxism and temporomandibular disorders (TMD). These resins were modified with graphene oxide (GO), graphene oxide functionalized (OGF) with hydrofluoric acid (HF), followed by the incorporation of sodium fluoride (NaF). Characterization analyses confirmed the effective chemical modification of the nanofillers, and the sample treated with 7.5 mL of HF (FGO_7.5) was selected for nanocomposite formulation due to its superior performance in the conducted tests. The GO, OGF, and NaF fillers were incorporated into the resin by sonication, and the samples were successfully obtained via 3D printing. Regarding mechanical properties, the Shore D hardness test revealed the maintenance of this property after the addition of the fillers (p > 0.05). Additionally, increased wear resistance was observed in all nanocomposites (p < 0.001), with the lowest values attributed to RES+GO (33%), RES+GO+NaF (37.9%), RES+NaF (41.7%), and RES+OGF (42.7%), whereas RES presented 52.4%. The addition of fillers did not affect the compressive strength of the samples (p < 0.05); however, it reduced their compressive elastic modulus compared to RES. Thermal analyses indicated greater resilience and flexibility in the samples containing nanofillers, with a reduction in storage modulus values, as well as in loss modulus and glass transition temperature (RES = 94.967 °C ± 0.404 °C; RES+GO = 80.667 °C ± 1.704 °C; RES+OGF = 80.3 °C ± 1.229 °C; RES+NaF = 80.033 °C ± 2.003 °C; and RES+GO+NaF = 80.033 °C ± 2.003 °C). Thermomechanical analysis demonstrated the maintenance of dimensional stability after filler addition within the clinical temperature range (25 °C to 50 °C), with the lowest value observed for RES+OGF (0.08704% ± 0.01498%) compared to RES (0.10219% ± 0.03337%). Thermogravimetric analysis (TGA) showed that the incorporation of fillers did not significantly alter the thermal degradation behavior. The evaluation of fluoride ion release in artificial saliva confirmed the presence of fluoride ions at all evaluated time points (24 h, 48 h, 7 d, 14 d, and 30 d), although the concentration of fluorinated fillers used (0.05%) was not sufficient to achieve the desired anticaries effect, as reported in the literature. Sorption and solubility analyses demonstrated adequate behavior for all formulations, and cell viability assays indicated biocompatibility and low cytotoxicity of the nanocomposites, suggesting their potential for clinical application. Based on the obtained results, it can be concluded that the incorporation of 0.05% FGO into acrylic resins for 3D printing represents the most promising and innovative strategy of this study, combining suitable properties with potential application for future functional optimization of polymeric materials in different fields of dentistry. [resumo fornecido pelo autor]