Caries Substrate — MFDS Part 1 MCQ

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EasyMicrobiologyCaries SubstrateMFDS Part 1

Which dietary substrate particularly promotes the cariogenicity of Streptococcus mutans by supporting both acid production and extracellular glucan synthesis?

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Correct answer: B — Sucrose

Sucrose is the single best answer. Streptococcus mutans can ferment sucrose, producing organic acids—predominantly lactic acid—which lower plaque pH and promote enamel demineralisation. Sucrose is especially cariogenic because its glucosyltransferases also use it to synthesise extracellular glucans. These glucans enhance bacterial adherence, biofilm structure and retention of acid at the tooth surface. Glucose, fructose and lactose can contribute to bacterial acid production, but they do not have sucrose's distinctive direct role as a glucosyltransferase substrate. Xylitol is a non-fermentable or poorly fermentable sugar alcohol and does not produce a comparable cariogenic acid response.

Reference: Paes Leme AF et al. The role of sucrose in cariogenic dental biofilm formation—new insight. Journal of Dental Research. 2006;85(10):878–887. https://pubmed.ncbi.nlm.nih.gov/16998125/