Bioactive hydrophobic bonding resins containing fluoroaluminosilicate particles and polyacrylic acid for experimental two-step self-etch adhesive systems: Mechanical behavior, ion release, cell viability, and calcium phosphate surface precipitation

Abstract

Objective To develop and characterize experimental bioactive hydrophobic bonding resins containing non-silanized fluoroaluminosilicate particles (Bio F) and polyacrylic acid (PAA) as part of a two-step self-etch adhesive system. Methods Non-silanized Bio F particles at 5 wt% or 10 wt%, with or without 2.5 wt% PAA, were incorporated into the hydrophobic phase of experimental self-etching adhesive systems. The materials were evaluated for cohesive strength, elastic modulus, alkalinizing activity, fluoride, calcium and phosphate ion release, cell viability, and apatite-related surface precipitation. Surface characterization was performed by scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD) after 28 days of storage in phosphate-buffered saline at 37 °C. Data were analyzed using one-way ANOVA and Holm-Sidak post hoc test (α = 0.05). Results Adhesive systems containing Bio F particles promoted alkalinization of the storage media throughout the experimental period. The formulation containing 10 wt% Bio F and PAA showed the highest release of fluoride, calcium and phosphate ions. The incorporation of Bio F particles, with or without PAA, did not significantly affect cohesive strength or elastic modulus compared with the control adhesive (p > 0.05). SEM/EDS and XRD analyses indicated the formation of calcium/phosphate-rich surface precipitates and apatite-related crystalline phases after immersion in PBS. Moderate cell viability values were observed, with statistically significant differences among groups (p < 0.05). Conclusions The incorporation of fluoroaluminosilicate particles and PAA modified the physicochemical behavior of experimental hydrophobic bonding resins by enhancing ion release, alkalinizing activity, and apatite-related surface precipitation, without compromising their intrinsic cohesive mechanical behavior. These formulations maintained moderate cell viability, representing a viable ion-releasing bonding phase for two-step self-etch adhesives.