Metabolic Activity of S. mutans Biofilm on Different Dental Composites

Objectives: This study evaluated the response of a Streptococcus mutans biofilm after being grown on three different dental composites, including an experimental hydrophobic composite developed with oxirane/acrylate functionality (Oasys).
Methods: Eighteen bars of each composite (Filtek Supreme, Admira VOCO, and Oasys) were formed in a mold and light-cured. Bars were incubated in 6-well plates with 10⁶ bacteria in Brain Heart Infusion media with 0.5% sucrose for the first 24 hours. Media (BHI without sucrose) was changed every 24 h at the same time without disturbing to propagate the biofilm adhered to the bars. Lactate production, metabolic activity, and viable cell counts after incubation with S. mutans biofilm were measured at 4 hours, 24 hours, and 15 days for each material. To test metabolic activity and colony-forming units, bars were transferred to sterile PBS and sonicated at 6V for 10 seconds. Lactate production of the biofilm was tested by sampling the media before the bars were removed for sonication. Lactate was measured with a BioVision kit with absorbance at 570 nm. The MTT (Vybrant® MTT Cell Proliferation Assay Kit) assay was performed only at 24 hours and 15 days, due to insufficient bacterial growth timethe times for which there was sufficient biofilm biomass. MTT was measured using the shortened protocol with 2h of incubation and measured at 540 nm.
Results: Two-way ANOVA was carried out (p≤0.05). No statically significant differences were noted among the composites for any of the tests. The number of colony-forming units increased linearly over the time points, being statistically higher at 15 days when compared to 4h and 24hrs. The same was observed for the lactate production of the biofilm. No significant difference was observed for the metabolic activity at 24hours and 15days.
Conclusions: Although the composites tested have different chemistry and composition, there was no significant difference among them in terms of changing affecting properties of the biofilms that coated them.