Antimicrobial Characteristics of QAMS-containing Resin Cement Against Streptococcus mutans Biofilm

Objective: To determine the antimicrobial efficacy of resin cement containing a novel quaternary ammonium, methacrylate-functionalized silicate (QAMS).  Methods: Specimens (d=7.64mm, h=1.75mm) of CHOICE2 (Bisco) resin cement with QAMS (experimental group; n=8) or without QAMS (control group; n=8) were polymerized against glass slides, and UV-sterilized. Streptococcus mutans (strain UA159) biofilms were grown microaerophilically on specimens (batch culture, 0.5X Tryptone-yeast extract medium with 10mM sucrose, 37°C, 100rpm; media replenished after 24h). After 48h of bacterial growth, specimens were stained (BacLightª LIVE/DEAD, Invitrogen) and imaged (Leica TCS SP2 MP; n=3 locations/specimen). The structure of the entire thickness of biofilms was quantified using the following parameters (ISA3D software): biovolume (BV; μm³), mean biofilm thickness (MT; μm), and biofilm roughness coefficient (BR). Groups were compared using Student's t-tests (α=0.05) to determine differences among biofilm structural parameters for live- (Syto-9 stain) and dead/damaged-cells (Propidium Iodide stain). Results: The biofilm structures in the experimental group had statistically smaller mean biovolume and higher mean bioroughness values of live and dead/damaged cells than the control group (p<0.01; table below), but no statistically significant differences were observed between live and dead cells (p>0.05). Visual analysis of cells at the interface demonstrated a predominance of dead cells in the experimental group. Quantification of the interface is pending. Mean ± standard deviation values were:

* indicates mean values in column that are not statistically different (p>0.05)

Conclusions: Analyses of the CLSM images and biofilm structural parameters corroborate the antimicrobial effects of QAMS, which demonstrated contact-killing of S. mutans biofilms grown in contact with the antimicrobial agent.