Evaluation of the physicochemical and adhesive properties of an etch-and-rinse adhesive system incorporated with magnesium whitlockite nanoparticles.

OBJECTIVE

To synthesize and characterize magnesium whitlockite nanoparticles (nMg-WH) to evaluate the physicochemical and adhesive properties of a conventional adhesive incorporating different concentrations of nMg-WH.

METHOD: nMg-WH were synthesized using a hydrothermal method and characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Six groups of adhesive systems were prepared with different concentrations of nMg-WH (wt%: 0 % [Control], 0.1 %, 0.2 %, 0.5 %, 1 %, and 2 %) to evaluate the degree of conversion (DC, %), viscosity (cP), water sorption (WS, µg/mm³), and solubility (SL, µg/mm³). Forty-eight molars (n = 8) were sectioned and randomized between groups and evaluated for contact angle (in degrees) and microshear bond strength (µSBS), before and after thermocycling (TC) involving 10,000 cycles with a 30-s immersion time at temperatures of 5 °C and 55 °C. Statistical analysis was performed using one-way ANOVA (DC, cP, WS and SL) or mixed ANOVA (µSBS), followed by Tukey's test for multiple comparisons (α = 0.05).

RESULTS

Regarding the physicochemical properties, the 0.2 % (51.3 ± 0.3), 0.5 % (49.0 ± 1.4), and 1 % (49.2 ± 1.9) nMg-WH groups showed significantly higher DC compared to the control (41.0 ± 0.2). The 0.2 % group presented the lowest contact angle (16.24 ± 7.79), indicating enhanced wettability. Viscosity increased proportionally with concentration, although 0.1 % (28.91 ± 0.75) remained comparable (p > 0.05) to the control (31.00 ± 1.08). WS and SL were not significantly affected at higher concentrations (0.5 %, 1 %, and 2 %). Before TC, the 0.1 % (32.1 ± 4.0) and 0.2 % (30.9 ± 2.1) nMg-WH groups demonstrated statistically higher (p < 0.05) µSBS values than the control (18.0 ± 5.2). After TC, concentrations of 0.2-2 % exhibited higher μSBS compared to the control, with the 0.5 % nMg-WH group showing the highest value (31.8 ± 1.0).

SIGNIFICANCE: nMg-WH improved the physicochemical properties of the adhesive system and increased adhesion to dentin, particularly at concentrations ranging from 0.2 % to 1 %.