Novel Dental Nanocomposites with Ion Recharge, Protein-Repellent and Antibacterial Capability

Objectives: (1) Develop a novel calcium (Ca) and phosphate (P) ion-rechargeable composite with protein-repellent and antibacterial activities; (2) Investigate the effects of nanoparticles of amorphous calcium phosphate (NACP), 2-methacryloyloxyethyl phosphorylcholine (MPC), and dimethylaminohexadecyl methacrylate (DMAHDM) on mechanical properties, protein adsorption, oral biofilms, and ion recharge and re-release.
Methods: The resin contained ethoxylated BisGMA and pyromellitic glycerol dimethacrylate (PMGDM). Composite formulations were: (1) Control (no MPC or DMAHDM); (2) 3% MPC; (3) 3% DMAHDM; (4) 3% MPC + 3% DMAHDM. Fillers consisted of NACP (20%) and glass particles (50%). Human saliva microcosm biofilm model was used to measure colony-forming units (CFU), live/dead, metabolic activity, and lactic acid. Protein adsorption, Ca and P ion recharge and re-release were determined.
Results: There was no significant difference in flexural strength (69.0±7.5)MPa and elastic modulus (7.0±0.6)GPa of MPC-DMAHDM composite compared to commercial control composite (p>0.1). MPC-DMAHDM had the strongest antibacterial effects compared with using MPC or DMAHDM alone (p<0.05). Total microorganisms CFU count on MPC-DMAHDM composite was (5.93±2.0)x10⁵ CFU/disk, 3 orders of magnitude lower than commercial control composite. Total streptococci and mutans streptococci CFU counts were also 3 orders magnitude lower on MPC-DMAHDM at (7.71±1.26)x10⁴ CFU/disk and (3.02±0.94)x10³ CFU/disk, respectively, compared to commercial control. All NACP composites showed high levels of Ca and P ion release, recharge and re-release. Adding MPC and DMAHDM did not compromise the ion rechargeability. Ion re-release after three cycles was similar to previous cycles, with Ca ion re-release of (0.98±0.02)mmol/L and P ion re-release of (0.2±0.01)mmol/L, indicating long-term remineralization capability.
Conclusions: Ca and P ion-rechargeable composites with protein-repellent and antibacterial abilities were developed. These composites had less biofilm metabolic activity and lactic acid, with CFU reduction by more than 3 logs. These novel Ca and P ion-rechargeable composites with protein-repellent and antibacterial properties are promising for tooth restorations.