Antibacterial and remineralizing nanocomposite inhibit root caries biofilms and protect root dentin hardness at the margins

Senior patients have a high incidence of tooth root caries. The objectives of this study were to: (1) develop a bioactive composite with calcium (Ca) and phosphate (P) ion-release and antibacterial capabilities via nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM); (2) inhibit root biofilms of Streptococcus mutans, Lactobacillus acidophilus and Candida albicans in a biofilm-based recurrent root caries model to protect root dentin hardness under biofilms for the first time. Five groups were tested: (1) Heliomolar nanocomposite (Commercial control); (2) Experimental composite control (0% NACP, 0% DMAHDM); (3) Remineralizing composite (30% NACP); (4) Antibacterial composite (3% DMAHDM); (5) Remineralizing and antibacterial composite (NACP + DMAHDM). Colony-forming units (CFU), lactic acid and polysaccharide of biofilms were evaluated. Demineralization of bovine root dentin with restorations was induced via multi-species biofilms, and root dentin hardness was measured. Adding NACP and DMAHDM into composite did not compromise the mechanical properties (p > 0.05). Biofilm lactic acid, polysaccharides and CFU were greatly reduced via DMAHDM (p