Novel antibacterial calcium phosphate nanocomposite with long-term ion recharge and re-release to inhibit caries

Abstract

Short-term studies on calcium-phosphate (CaP) ion-rechargeable composites were reported. The long-term rechargeability is important but unknown. The objectives of this study were to investigate nanocomposite with strong antibacterial and ion-recharge capabilities containing dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and evaluate long-term ion-recharge by testing for 12 cycles (taking 6 months to complete) for the first time. Three groups were tested: (1) Heliomolar control; (2) Resin+20%NACP+50%glass; (3) Resin+3%DMAHDM+20%NACP+50%glass. Biofilm acid and colony-forming units (CFU) were measured. Ion-recharge was tested for 12 cycles. NACP-DMAHDM composite reduced biofilm acid, and reduced CFU by 4 logs. High levels of ion releases were maintained throughout 12 cycles of recharge, maintaining steady-state releases without reduction in 6 months (p>0.1), representing long-term remineralization potential. Bioactive nanocomposite demonstrated long-term ion-rechargeability for the first time, showed remineralization and potent anti-biofilm functions, with promise for tooth restorations to combat caries.

The Antibacterial and Remineralizing Effects of Biomaterials Combined with DMAHDM Nanocomposite: A Systematic Review

“…All studies reported that composites with DMAHDM had significantly reduced live bacteria than control composites. Among the ten studies that assessed the antibacterial potential of NACP alone, all reported similar results to control composites where bacteria were primarily alive, indicating NACP did not have any additional antibacterial effects with DMAHDM [ 1 , 2 , 37 , 42 , 46 ]. Composites with MPC alone showed lower levels of bacterial adhesion but the bacteria were found to be mostly alive; however, when combined with DMAHDM, there were less biofilms and the bacteria had mostly compromised cell membranes [ 3 , 38 , 40 , 43 , 44 , 45 ] with no significant changes in results after 180 days of water-aging [ 45 ].…”

“…All studies used a modified Menschutkin reaction method to synthesize DMAHDM [ 2 ]. NACP was synthesized with a spray-drying technique [ 37 ].…”

“…Dental composite resins are widely used restorative materials due to their ability to conserve tooth structure during cavity preparation, aesthetics and direct-filling capabilities [ 1 , 2 , 3 , 4 ]. However, composite resin restorations still present several drawbacks including polymerization shrinkage, bulk fracture, mechanical fatigue by mastication, marginal leakage and biodegradation by acid while also being challenged by the adhesion and accumulation of cariogenic bacteria (Viz., Streptococcus mutans and Lactobacilli ) when compared to other materials used for restoration [ 1 , 2 , 5 ].…”

“…When copolymerized in resins, quaternary ammonium methacrylates (QAMs), which are cationic compounds, exhibit low toxicity and a broad-spectrum antimicrobial effect [ 2 , 10 , 11 , 12 ]. These positively charged methacrylic monomers bind and disrupt the electrical equilibrium of the negatively charged bacterial membranes thereby causing rupture and cell death [ 13 ].…”

“…The antibacterial efficacy of QAMs has been correlated with the alkyl chain length (CL) of the hydrocarbons as this causes an increase in hydrophobicity [ 2 , 14 , 15 ]. Previous studies have reported that an increase in CL from 3 to 16 greatly enhanced the efficacy of dental materials against bacteria [ 16 ], which then decreased at a CL of 18 [ 17 , 18 ].…”