Development of a multifunctional adhesive system for prevention of root caries and secondary caries

• A novel adhesive for prevention of tooth root caries and secondary caries was developed containing a protein-repellent agent, an antibacterial monomer, and remineralization nanoparticles for the first time.
• A single coat of this adhesive on tooth root dentin produced a coating thickness of approximately 70 μm and completely sealed all dentinal tubules to provide a barrier against biofilm acids.
• In addition, this adhesive resin had a 95% reduction in protein adsorption, was strongly antibacterial, and reduced biofilm colony-forming units by four orders of magnitude.
• Therefore, this novel multifunctional adhesive with strong protein-repellent, antibacterial and remineralization properties is promising to coat tooth roots to prevent root caries, as well as to bond restorations in tooth cavities to inhibit secondary caries.
• The combined use of triple agents (protein-repellent agent, antibacterial agent, and remineralization agent) may have wide applicability in bonding agents, cements, sealants and composites to inhibit caries.

ObjectivesThe objectives of this study were to: (1) develop a novel adhesive for prevention of tooth root caries and secondary caries by possessing a combination of protein-repellent, antibacterial, and remineralization capabilities for the first time; and (2) investigate the effects of 2-methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM), and nanoparticles of amorphous calcium phosphate (NACP) on dentin bond strength, protein-repellent properties, and dental plaque microcosm biofilm response.MethodsMPC, DMAHDM and NACP were added into Scotchbond Multi-Purpose primer and adhesive. Dentin shear bond strengths were measured. Adhesive coating thickness, surface texture and dentin–adhesive interfacial structure were examined. Protein adsorption onto adhesive resin surface was determined by the micro bicinchoninic acid method. A human saliva microcosm biofilm model was used to investigate biofilm metabolic activity, colony-forming unit (CFU) counts, and lactic acid production.ResultsThe resin with 7.5% MPC + 5% DMAHDM + 30% NACP did not adversely affect dentin shear bond strength (p > 0.1). The resin with 7.5% MPC + 5% DMAHDM + 30% NACP produced a coating on root dentin with a thickness of approximately 70 μm and completely sealed all the dentinal tubules. The resin with 7.5% MPC + 5% DMAHDM + 30% NACP had 95% reduction in protein adsorption, compared to SBMP control (p < 0.05). The resin with 7.5% MPC + 5% DMAHDM + 30% NACP was strongly antibacterial, with biofilm CFU being four orders of magnitude lower than that of SBMP control.Significance The novel multifunctional adhesive with strong protein-repellent, antibacterial and remineralization properties is promising to coat tooth roots to prevent root caries and secondary caries. The combined use of MPC, DMAHDM and NACP may have wide applicability to bonding agents, cements, sealants and composites to inhibit caries.