Shear bond strength of metal orthodontic brackets bonded to artificially demineralized enamel treated with three remineralizing agents bonded with AgNP-modified adhesive: An in vitro study

OBJECTIVE: This in vitro study evaluated the strength of the shear bond (SBS) between metal orthodontic brackets and demineralized enamel following remineralization using Self-Assembling Peptide P11-4 (SAP), casein-amorphous calcium phosphate (CPP-ACP), and a laboratory-prepared tricalcium silicate (TCS) paste. Silver nanoparticles (AgNPs) impact on the adhesive system was also examined. METHODS: Five groups were formed from one hundred removed premolars: (n=20) sound enamel, demineralized enamel, and three remineralized groups (Curodont™, MI Paste Plus®, TCS paste). Each was split into two smaller groups (n=10) based on the kind of used adhesive into conventional adhesive or AgNPs containing. A universal testing machine was used to quantify SBS, and SEM-EDX was used to assess the surface content of Ca, P, and F. The failure mode was identified using the Adhesive Remnant Index (ARI). The data were analysed statistically by two-way ANOVA for SBS, one way ANOVA for EDX and the Kruskal-Wallis H-test for ARI. The significance level was set at P≤0.05. RESULTS: The TCS paste group demonstrated the highest SBS values under both adhesive conditions, with 7.83, 7.92MPa for conventional adhesive and AgNPs containing. While demineralized enamel showed the lowest with 3.91,3.75MPa for both adhesives, AgNPs incorporation significantly reduced SBS in all groups P≤0.001. Curodont™ showed the highest mineral uptake with Ca (50.25), P (20.59) and F (1.00). ARI patterns were not significantly altered by AgNP incorporation in all groups. CONCLUSION: SBS was significantly influenced by the type of remineralizing agent, with the TCS paste group demonstrating the most favourable SBS outcomes among the materials tested. Remineralization significantly enhanced the bonding performance of orthodontic brackets on previously demineralized enamel surfaces. Among the remineralizing agents, Curodont™ Protect exhibited the greatest remineralization efficacy. The incorporation of AgNPs into the adhesive system adversely affected the bond strength in all groups.