Effect of Mesoporous Zinc Oxide Nanoparticle Incorporation on the Bond Strength of Resin‐Modified Glass Ionomer Cement to Enamel and Dentin: An In Vitro Study

<b>Objective:</b> The purpose of this in vitro study was to evaluate the microshear bond strength (µSBS) of resin-modified glass ionomer cement (RMGIC) to enamel and dentin, with and without the inclusion of zinc oxide nanoparticles (ZnO NPs) and mesoporous ZnO NPs. <b>Materials and Methods:</b> 140 extracted human third molars were used, categorized into two primary groups based on the substrate-enamel or dentin-and further divided into seven subgroups (<i>n</i> = 10). The groups consisted of RMGIC alone, and RMGIC enhanced with either 3%, 5%, or 7% of conventional ZnO NPs or mesoporous ZnO NPs. µSBS testing was performed, followed by statistical evaluation. <b>Results:</b> The type of substrate and the incorporation of NPs significantly affected bond strength (<i>p</i> < 0.001), with enamel showing superior µSBS compared to dentin (<i>p</i> < 0.001). The subgroup containing 5% mesoporous ZnO NPs demonstrated the highest bond strength overall (<i>p</i> < 0.001), while no significant variations were detected among the other groups (<i>p</i> > 0.05). <b>Conclusion:</b> Enhancing RMGIC with 5 wt.% mesoporous ZnO NPs markedly improved adhesion to both enamel and dentin. Increasing the (nanoparticle) NP concentration beyond 5% did not further enhance bonding performance. Enamel exhibited consistently better bonding than dentin in all subgroups. These results highlight the potential of 5% mesoporous ZnO NPs in improving the clinical efficacy of RMGIC.