Novel Bioactive Resin Coating with Calcium Phosphate Nanoparticles for Antibacterial and Remineralization Abilities to Combat Tooth Root Caries

Tooth root caries account for 10.1% of all dental caries in the USA. This study developed a multifunctional resin coating with calcium (Ca) and phosphate (P) ion release and antibacterial properties to combat root caries. The effects of nano-sized amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) on mechanical, physical, and antibacterial properties against <i>Streptococcus mutans</i>, and cytotoxicity on dental pulp stem cells and gingival fibroblasts were evaluated. A coating resin combining urethane dimethacrylate (UDMA), triethylene glycol divinylbenzyl ether (TEGDVBE), DMAHDM, and NACP was synthesized and compared with Seal&Protect and Vanish XT. Experimental groups (UV + 5% DMAHDM + 10%, 15%, and 20% NACP) showed flexural strength (70.9 ± 8.0 to 81.1 ± 6.0) MPa, significantly higher than Seal&Protect (48.2 ± 7.2) MPa (<i>p</i> < 0.05) and comparable to Vanish XT (70.2 ± 13.6) MPa, (<i>p</i> > 0.05). Elastic modulus (2.2 to 3.3) GPa was lower than Vanish XT (9.4 ± 1.1) GPa (<i>p</i> < 0.05). Experimental groups showed an 8 log CFU reduction, 96% reduction in metabolic activity and 87% in lactic acid production, and increased Ca (1.25 ± 0.03) mmol/L and P (0.8 ± 0.001) mmol/L release over 35 days. Cytotoxicity for experimental groups against dental pulp stem cells and human gingival fibroblast was low and matched those of commercial controls already used in clinic. The resin demonstrated potent antibacterial properties, high ion release, low cytotoxicity, and maintained physical and mechanical integrity, offering potential to prevent root caries formation and progression.