Adhesive bond integrity of silanized zirconia nanoparticles in polymeric resin dentin bonding agent. An FTIR, SEM, and micro-tensile experiment

The aim of this in vitro investigation was to synthesize and silanize zirconia oxide (ZrO₂) nanoparticles with 3-methacryloxypropyltrimethoxysilane (MPS) and incorporate into two-step self-etch dentin adhesive at 2.5% and 5% concentrations to study the mechanical and biological properties at the dentin-resin interface. The silanized nanoparticles were investigated for their morphology, physicochemical properties, and spectral analysis. The modified experimental dentin adhesives were characterized in terms of cytotoxicity, degree of conversion (DC), micro-tensile bond strength (μ-TBS), 4-point bending strength (BS) and percentage of nano-leakage at different storage times. Among the experimental group, the adhesive specimen modified with 2.5% MPS-ZrO₂ nanofiller exhibited the highest mean DC % (∼42%), which was comparable to the control (44%) along with least cytotoxicity after 72 h (p <0.001). Likewise, the 2.5% MPS-ZrO₂ nanofiller had shown the highest micro-tensile bond strength (39.9 ± 7.8) and 4-point bending strength (55.0 ± 18.4) after ageing, both of which were significantly higher than the control adhesive, respectively (p <0.05). Furthermore, after ageing 2.5% MPS-ZrO₂ nanofiller has shown a significant lower mean nano-leakage % (8.3 ± 2.6) than the control (27.6 ± 13.8) after ageing. Dentin bonding agent modified with 2.5% MPS-ZrO₂ nanofiller substantially increased bond integrity at the resin-dentin interface.