Three-dimensional biofilm properties on dental bonding agent with varying quaternary ammonium charge densities

Abstract

Objectives Tooth-restoration interfaces are the weak link with secondary caries causing restoration failure. The objectives of this study were to develop an antimicrobial bonding agent with dimethylaminododecyl methacrylate (DMAHDM), and investigate the effects of quaternary amine charge density on three-dimensional (3D) biofilms on dental resin for the first time. Methods DMAHDM was synthesized and incorporated into Scotchbond Multi-Purpose bonding agent at mass fractions of 0% (control), 2.5%, 5%, 7.5% and 10%. Streptococcus mutans bacteria were inoculated on the polymerized resin and cultured for two days to form biofilms. Confocal laser scanning microscopy was used to measure biofilm thickness, live and dead biofilm volumes, and liv bacteria percentage in 3D biofilm vs. distance from resin surface. Results Charge density of the resin had a significant effect on the antibacterial efficacy (p < 0.05). Biofilms on control resin had the greatest thicknesses. Biofilm thickness and live biofilm volume decreased with increasing surface charge density (p < 0.05). There were significant variations in bacterial viability along the 3D biofilm thickness (p < 0.05). At 2.5% and 5% DMAHDM, the bacterial inhibition was the greatest on or near the resin surface, and the killing effect decreased away from the resin surface. At 10% DMAHDM, the entire 3D biofilm was dead and the percentage of live bacteria was nearly 0% throughout the biofilm thickness. Conclusions Adding new antibacterial monomer DMAHDM into dental bonding agent yielded a strong antimicrobial activity, substantially decreasing the 3D biofilm thickness, live biofilm volume, and percentage of live bacteria on cross-sections through the biofilm thickness. Significance Novel DMAHDM-containing bonding agent with capability of inhibiting 3D biofilms is promising for a wide range of dental restorative and preventive applications to inhibit biofilms at the tooth-restoration margins and prevent secondary caries.

Quaternary ammonium-based biomedical materials: State-of-the-art, toxicological aspects and antimicrobial resistance

“…It was previously perceived that polymerized "contact killing" antibacterial resin polymers exhibit antimicrobial activities only via direct contact of bacteria, without antibacterial effects against planktonic (free-floating) bacteria [349]. However, recent studies of QA-containing materials conducted with confocal laser scanning microscopy and three-dimensional reconstruction of biofilms stained with live-dead fluorescent stains [350,351] indicate that those materials possess a reducing spectrum of biocidal activities from the substrate surface to the top of the biofilms [230,288,289,352,353]. That is, the presence of dead microorganisms is not limited to the bottom of the biofilms that is in contact with the antibacterial surface.…”

Human <em>in situ </em>Study of the Effect of bis(2-methacryloyloxyethyl) Dimethylammonium Bromide Immobilized in Dental Composite on Controlling Mature Cariogenic Biofilm

“…Indeed, the live/dead images obtained at the initial period of biofilm formation showed the presence of a higher proportion of nonviable bacteria (red-orange color areas). Accordingly, previous studies have highlighted similar viability of 3D biofilms growing on resin-based materials containing quaternary ammonium monomers[35,36]. Furthermore, Beyth and co-workers have suggested an intracellularly mediated death program, in which, the bacterial lysis promoted by the presence of quaternary ammonium on the resin surface may function as a stressful condition triggering programmed cell death to the bacteria further away in the biofilm[25,37].Subsequently, no expressive microbial reduction results on CFU values or microorganism proportions were observed for S. mutans, and the others evaluated culture media after the 14-day period.…”

Developing a New Generation of Therapeutic Dental Polymers to Inhibit Oral Biofilms and Protect Teeth

“…In a study on three-dimensional (3D) biofilms grown on dental polymer surfaces, the percentage of live bacteria was determined as a function of the location of the 2D cross-section inside the 3D biofilm at various distances from the polymer surface [ 91 ]. Near the surface of the polymer which contained DMAHDM, there were more dead bacteria in the biofilm.…”

“…Near the surface of the polymer which contained DMAHDM, there were more dead bacteria in the biofilm. In the 3D biofilm away from the polymer surface, the percentage of live bacteria increased, likely due to a decrease in the contact-inhibition efficacy [ 91 ]. These results are consistent with the results of the DMAHDM-containing endodontic sealer, which achieved a greater reduction in the biofilm CFU at 3 days, compared to the reduction at 14 days [ 90 ].…”