Degradation of Dental Resin Composites and Adhesives by Enterococcus Faecalis

Gitalis, Russel 1, 2 ;  Marashdeh, Muna 1, 2 ;  Finer, Yoav 1, 2

1. Faculty of Dentistry, University of Toronto; 2. Institute of Biomaterials and Biomedical Engineering, University of Toronto

Background: Dental root-canal infections are caused by bacterial penetration into the root-canal system. Post root-canal treatment, the interface between root-canal dentin-sealer undergoes degradation over time, allowing for microbial biofilm penetration. Human saliva and cariogenic bacteria contain esterase-like activities, which have shown to accelerate the degradation of methacrylate-based resin composites and adhesives, increasing microbial interfacial ingress. Enterococcus faecalis (E. faecalis) is a bacterium commonly detected in failed root-canal treated teeth and could degrade the root-canal dentin-methacrylate resin interface.

Objectives/Hypothesis: Measure esterase-like, cholesterol esterase-like (CE-like) and pseudocholinesterase-like (PCE-like) activities of E. faecalis. Assess the effect of the bacteria on the degradation of methacrylate resin composite, total-etch and self-etch adhesives.

Materials & Methods: CE-like and PCE-like activities from E. faecalis were measured with nitrophenyl and butyrylthiocholine substrates, respectively. The ability of E. faecalis to degrade composite, total-etch and self-etch adhesives was examined by quantifying the release of bishydroxy-propoxy-phenyl-propane (BisHPPP), a universal resin degradation byproduct, using high performance liquid chromatography (N=3/material).

Results: E. faecalis expressed CE-like (1.23±0.13units/µg dry bacteria), but no PCE-like activity, comparable to Streptococcus mutans UA159; a species that degrades resin composite and adhesives. After 30 days and/or 14 days of incubation the amount of BisHPPP released was higher in the presence of bacteria verses media only for total-etch adhesive and composite but not self-etch adhesive (p<0.05). The amount of BisHPPP released after 30 days of incubation with bacteria was significantly different between composite (3.43±1.20µg/cm2), total-etch (23.69±1.72µg/cm2) and self-etch (0.86±0.44µg/cm2) adhesives (p<0.05).

Conclusions: E. faecalis possess esterase-like degradative activity towards dental methacrylate resin restoration materials, which could accelerate the degradation of the dentin-methacrylate resin interface, increasing bacterial penetration into the root-canal system.

Significance/Impact: The degradative activity of E. faecalis were material dependent, and could guide the development of biostable and/or anti-degradative activity restoration materials, increasing marginal biostability of the root-canal dentin-resin interface.