Evaluation of antibacterial and remineralizing nanocomposite and adhesive in rat tooth cavity model

Antibacterial and remineralizing dental composites and adhesives were recently developed to inhibit biofilm acids and combat secondary caries. It is not clear what effect these materials will have on dental pulps in vivo. The objectives of this study were to investigate the antibacterial and remineralizing restorations in a rat tooth cavity model, and determine pulpal inflammatory response and tertiary dentin formation. Nanoparticles of amorphous calcium phosphate (NACP) and antibacterial dimethylaminododecyl methacrylate (DMADDM) were synthesized and incorporated into a composite and an adhesive. Occlusal cavities were prepared in the first molars of rats and restored with four types of restoration: control composite and adhesive; control plus DMADDM; control plus NACP; and control plus both DMADDM and NACP. At 8 or 30 days, rat molars were harvested for histological analysis. For inflammatory cell response, regardless of time periods, the NACP group and the DMADDM + NACP group showed lower scores (better biocompatibility) than the control group (p = 0.014 for 8 days, p = 0.018 for 30 days). For tissue disorganization, NACP and DMADDM + NACP had better scores than the control (p = 0.027) at 30 days. At 8 days, restorations containing NACP had a tertiary dentin thickness (TDT) that was five- to six-fold that of the control. At 30 days, restorations containing NACP had a TDT that was four- to six-fold that of the control. In conclusion, novel antibacterial and remineralizing restorations were tested in rat teeth in vivo for the first time. Composite and adhesive containing NACP and DMADDM exhibited milder pulpal inflammation and much greater tertiary dentin formation than the control adhesive and composite. Therefore, the novel composite and adhesive containing NACP and DMADDM are promising as a new therapeutic restorative system to not only combat oral pathogens and biofilm acids as shown previously, but also facilitate the healing of the dentin–pulp complex.