Silver Phosphate as Antimicrobial and Remineralizing Agent in Orthodontic Adhesives

Objectives: This study explores using silver phosphate (Ag₃PO₄) nanoparticles for antibacterial and remineralizing orthodontic adhesives
Methods: Ag₃PO₄ nanoparticles were synthesized through coprecipitation and characterized by XRD, SEM, EDS, Raman spectroscopy, and laser diffraction. An orthodontic adhesive was formulated with BisGMA and TEGDMA blend in the resin matrix and 80 wt% quartz and 2.5 wt% silica as fillers. The particles were incorporated into orthodontic adhesives at concentrations of 0.5 wt%, 1 wt%, and 2 wt%. Physicochemical and biological properties were assessed through polymerization kinetics, softening in solvent, cytotoxicity, shear bond strength, antibacterial activity against Streptococcus mutans and mineral deposition over time.
Results: Ag₃PO₄ was successfully synthesized with 190nm median size (d₁₀ 69nm -d₉₀ 208nm), 27.9 m²/g of specific surface area and irregular shape. All groups with Ag₃PO₄ presented reduced reduction in degree of conversion and maximum polymerization rate. The ΔKHN% in the softening in solvent was not influenced by Ag₃PO₄. No cytotoxic effect was observed, with all groups reaching at least 100% viability. Shear bond strength was higher in the control group and 1 wt% groups compared to the 0.5 wt% and 2 wt% groups. No effect on planktonic bacteria was detected in the antibacterial analysis. The adittion of 1 wt% inhibited immediate biofilm formation, while the 2 wt% concentration reduced biofilm formation after storage. Mineral deposition test revealed phosphate deposition in groups with Ag₃PO₄.
Conclusions: Ag₃PO₄ particles affected the polymerization in the developed materials, while maintained the bond strength, inhibition of biofilm formation, and mineral deposition.