Objectives:Develop bonding agent with double benefits of antibacterial and remineralizing capabilities, investigate the effects of nanoparticles of amorphous calcium phosphate (NACP) filler level and solution pH on calcium (Ca) and phosphate (P) ion release from adhesive, and examine the antibacterial and dentin bond properties.
Methods: NACP and a quaternary ammonium monomer (dimethylaminododecyl methacrylate, DMADDM) were synthesized. Scotchbond Multi-Purpose (SBMP) served as control. DMADDM was mixed into primer and adhesive at 5 mass%. NACP was mixed into adhesive at 10, 20, 30 and 40 mass%. A dental plaque microcosm biofilm model using human saliva was tested. Ca and P ion releases from adhesive were measured at pH 7, 5.5 and 4.
Results: Adding 5% DMADDM and 10-40% NACP into bonding agent, and water-aging for 28 days, did not adversely affect dentin bond strength, compared to SBMP control at 1 day (p>0.1) (mean±sd; n=10). Adding DMADDM into bonding agent substantially decreased the biofilm metabolic activity from 0.23 to 0.10 (p<0.05). Biofilm lactic acid production was decreased from 27 to 10 mmol/L (p<0.05). Increasing NACP from 10% to 40% increased the Ca and P release by an order of magnitude. Decreasing pH from 7 to 4 increased the ion release: At 40% NACP, Ca was increased from 2.1 to 13.2 mmol/L, and P from 0.6 to 7.0 mmol/L (p<0.05).
Conclusions: Bonding agent containing antibacterial DMADDM and remineralizer NACP greatly inhibited biofilm viability and acid production. Ca and P release increased with NACP filler level from 10% to 40%. NACP adhesive was “smart” and dramatically increased the ion release at cariogenic pH4, when these ions would be most-needed to inhibit caries. The novel DMADDM-NACP bonding agent is promising to inhibit biofilms and remineralize tooth lesions, thereby increasing the restoration longevity.