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Effect of Polymer Degree of Conversion on Streptococcus mutans Biofilms



Alison M. Kraigsley, Kathy Tang, John A. Howarter, Katrice Lippa, Sheng Lin-Gibson, Nancy Lin


The effects of key material properties of polymeric composite restorations on cariogenic oral biofilms are needed to provide insight into the materials' role in recurrent caries. The objective of this study was to quantify the effects of degree of conversion (DC) on Streptococcus mutans (S.. mutans) biofilm growth and test chemical factors that may contribute to that effect. Dental polymers were fabricated with a DC of 52 % or 76 %, pre-conditioned with salivary pellicles, and inoculated. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and crystal violet (CV) were used to quantify metabolic activity and biomass, respectively, of intact biofilms at 4 h and 24 h. Surface methacrylates and leachables, two chemical factors that increase as DC decreases, were individually evaluated for effects on biofilms to further determine the cause of DC on biofilm properties. Low DC polymers reduced adherent biofilm metabolic activity but not biomass at 24 h. Leachables from low DC polymers had a similar effect as low DC polymers, whereas methacrylate functionalized surfaces had little effect. Overall, DC has significant impact on metabolic activity of 24 h S. mutans biofilms, and leachables play a major role in this effect. Utilizing both MTT and CV enabled the assessment of S. mutans biofilms under clinically relevant conditions without the need for biofilm harvesting.
Macromolecular Bioscience


Bacteria, Dental restorative material, Biofilm, Monomer, MTT assay, Photopolymerisation


Kraigsley, A. , Tang, K. , Howarter, J. , Lippa, K. , Lin-Gibson, S. and Lin, N. (2012), Effect of Polymer Degree of Conversion on Streptococcus mutans Biofilms, Macromolecular Bioscience (Accessed May 25, 2024)


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Created October 4, 2012, Updated October 12, 2021