Novel Antibacterial Nano-Structured Resin Coatings to Suppress Biofilms and Inhibit Secondary Caries Around Dental Crowns

Abstract

Biofilm accumulation at restoration and provisional crown margins poses a significant risk for secondary caries, a leading cause of restorative failure, necessitating repeated interventions and contributing to progressive tooth structure loss. Over prolonged prosthodontic treatment, material surfaces become increasingly susceptible to bacterial colonization, degradation, and wear, underscoring the need for multifunctional coatings with durable antibacterial properties. Consequently, this dissertation endeavors to introduce a novel multifunctional resin-based coating material incorporating dimethylaminododecyl methacrylate (DMADDM) as an antibacterial agent to inhibit the biofilm formation, nanoparticles of amorphous calcium phosphate (NACP), and calcium fluoride nanoparticles (nCaF2) as remineralizing agents within a urethane dimethacrylate/triethylene glycol divinylbenzyl ether (UDMA/TEG-DVBE) matrix, with the potential to increase the longevity of provisional restorations and protect adjacent tooth structure. All novel coating formulations were subjected to a series of antibacterial, physicochemical, mechanical, and ion release assessments. First, we investigated the optimal concentration of DMADDM that could be incorporated into a resin coating without compromising surface characteristics or biocompatibility. We found that DMADDM incorporated into the coating inhibited Streptococcus mutans (S. mutans) biofilm in a dose- dependent manner, with 10% identified as the optimal concentration, achieving an 8-log reduction in colony-forming units while maintaining favorable surface roughness and excellent biocompatibility with human gingival fibroblasts. Next, we investigated the physicochemical properties, bonding performance, wear resistance, and remineralizing ion release of coatings incorporating 10% DMADDM combined with NACP, nCaF2, or both. All formulations achieved clinically acceptable polymerization, superior shear bond strength, approximately 40% lower wear depth than the commercial control, and sustained release of calcium, phosphate, and fluoride ions for 70 days. Lastly, we investigated the antibacterial durability of the multifunctional coatings against salivary biofilms before and after simulated toothbrushing. The coatings achieved 4–6-log reductions in total viable counts and streptococci, with significant suppression of biofilm metabolic activity and lactic acid production that was largely retained following 10,000-cycle brushing simulation. These bioactive nano-structured resin coatings represent a promising multifunctional strategy with durable antibacterial, remineralizing, and wear-resistant capabilities, with the potential to reduce secondary caries and extend the clinical longevity of provisional restorations.