Development of a New Generation of Dental Rechargeable Nanocomposites with Anti-caries Properties

Abstract

Dental composites are popular for tooth cavity restorations due to their aesthetics, conservative approach, and direct-filling abilities. However, composite restorations have limited lifetime due to several limitations, including secondary caries, fracture, minimal abrasion and wear resistance and higher marginal leakage. Indeed, secondary caries is the primary reason for composite restoration failure. Besides, several studies have shown that conventional dental composites accumulate more biofilms/plaque when compared to other restorative materials. Therefore, this dissertation aims to develop a new generation of dental composites with antibacterial effects, protein-repellent activities, and remineralization properties. Recently, a rechargeable composite was developed, but this composite has no antibacterial or protein-repellent activities. In this dissertation projects, the nanoparticles of amorphous calcium and phosphate (NACP) as remineralizing agent, dimethylaminohexadecyl methacrylate (DMAHDM) as an antibacterial monomer, and 2- metha-cryloyloxyethyl phosphorylcholine (MPC) as a protein-repellent agent were incorporated into the rechargeable composite for the first time. Mechanical properties of the new nanocomposites were evaluated. The characterization of protein adsorption was measured. A human saliva microcosm biofilm model was used to determine biofilm metabolic activity, lactic acid, and colony-forming units (CFU). Calcium (Ca) and Phosphate (P) initial ion release, recharge and re-release were investigated. All rechargeable nanocomposites have good mechanical properties that were compared to those of a commercial composite. The rechargeable nanocomposites containing MPC showed the ability to reduce protein adsorption, as well as the biofilm metabolic activity, lactic acid, and CFU. The rechargeable nanocomposites containing DMAHDM showed strong antibacterial properties through the great inhibition of biofilm metabolic activity and lactic acid, and CFU. The incorporation of bioactive agents did not compromise the Ca and P initial ion release and rechargeability. The release was maintained at the same level with increasing number of recharge cycles, indicating long-term ion release. Therefore, this new generation of rechargeable nanocomposites with long-term Ca and P ion release, antibacterial and protein-repellent activities will provide the needed therapeutic effects to remineralize and strengthen the tooth structures, prolong the restoration longevity, and inhibit secondary caries.