Analysis of Biofilm Formed on Dental Composite Resins

Studies showed that modern dental resin composites contain a great variety of different monomers and additives. Because of this complex chemical composition and the incomplete monomer–polymer conversion, numerous substances may be released from set resin composite restorations into tissues of the oral cavity. Monomers were shown to promote the proliferation of the important cariogenic bacteria. The Objective: of this study was to compare and quantitate the biofilm formed on four composite materials. The differences in accumulation of salivary pellicle on composites were also analyzed. Materials and Methods: ATCC strains, Streptococcus mutans GS-5, and C211, S. sanguis Challis, and Actinomyces naeslundii12104 were grown for 24 hours and then suspended (1X10⁷ cells/ml). Cylindrical specimens (5 mm by 2mm) of four composite resins, GC Kalore®, SDR®, Filtek® Supreme, and Esthet-X® were prepared. Discs were sterilized and coated with human saliva. Six samples of each composite disc were incubated with 1.0ml of bacterial suspension and incubated for 48 hours. The number of adherent bacteria was determined by XTT reduction assay. The accumulation of salivary pellicle was determined by Western blot analysis using carbonic anhydrase specific antibodies. Results: Among the four composites, SDR and Esthet-X harbored 44±12%, and 38±11%, of the bacterial inoculum respectively. Significantly (P<0.05) less bacteria were found adhered (15±6%) to other composites. Analysis of salivary pellicles by Western blot assay showed abundance of carbonic anhydrase component of saliva on SDR and Esthet-X discs. Conclusion: The results show that composite surfaces affect the adsorption of salivary pellicle and accumulation of biofilm. Differences in support of biofilm by composite restorations should be taken into consideration for clinical applications. The study was supported by the College of Dentistry Alumni Research Foundation.