Incorporação de nanobastões de whitlockita de magnésio em sistema adesivo convencional: síntese hidrotérmica, caracterização, propriedades físico-químicas e adesão dentinária

Abstract

Magnesium whitlockite (Mg-WH) is a calcium phosphate that represents the second most abundant bone mineral and has aroused interest due to its potential in biomedical applications. This compound has properties that may be advantageous for bone and tooth regeneration, such as biocompatibility, bioactivity and ability to promote the formation of mineralized tissue. To date, there are no records in the literature of studies exploring the use of magnesium whitlockite nanorods (nMg-WH) as a dentin biomodifier. The present study aimed to synthesize and characterize nMg-WH in order to evaluate the physicochemical and adhesive properties of a conventional adhesive system with different concentrations of nMg-WH. For this purpose, such nanoparticles were obtained by hydrothermal synthesis and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning transmission electron microscopy (TEM). Then, six groups with different concentrations of nMg-WH in the adhesive system were formed (0% [Control], 0.1%, 0.2%, 0.5%, 1% and 2%) to evaluate the physicochemical properties, including the degree of conversion (%), viscosity (cP) and water sorption/solubility (μg/mm3). Forty-eight molars (n=8) were sectioned to expose dentin, randomly distributed among the six groups and evaluated for contact angle (°) and microshear bond strength (μSBS) in 2 times (before vs. after thermocycling). Artificial aging to simulate 1 year was performed according to the following parameters: 10,000 cycles and 30-s run time at temperatures of 5 °C and 55 °C. One-way ANOVA and mixed ANOVA, both followed by Tukey's test, were the tests used to evaluate the physicochemical properties and dentin adhesion, respectively. XRD identified that brushite has a monoclinic structure and nMg-WH as a rhombohedral crystal structure. FTIR vibrational modes identified the sample phases in BRU and nMg-WH through specific peaks. TEM with EDS detected a Mg2+ peak only in the nMg-WH sample. The analysis of the μSBS showed a significant interaction between the factors Group x Time (F(5)=24.99; p<0.001). Before aging, the Mg-WH 0.1% (32.0 ± 3.9) and 0.2% (30.8 ± 2.0) groups had the highest μSBS values, both statistically higher (p<0.05) than the control (17.9 ± 5.2), but did not maintain this union stability after thermocycling. After aging, concentrations between 0.2% and 2% showed μSBS higher than the control, especially Mg-WH 0.5%, which obtained the highest μSBS value (31.81 ± 1.01) among all groups. In addition, the Mg-WH 0.2%, 0.5% and 1% groups stood out for presenting better performance in relation to the control in the CG, in the contact angle the wettability was maintained or improved, with 10 similar sorption/solubility and increased viscosity, without compromising the μSBS. Thus, within the limitations of the study, nMg-WH improved the physicochemical properties of the adhesive system and provided better adhesion to dentin, especially in concentrations of 0.2% to 1%.