Root Caries Microbiology — NDEB AFK MCQ

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ModerateBiomedical SciencesRoot Caries MicrobiologyNDEB AFK

Which organism has been implicated in the progression of root surface caries (root caries) alongside Streptococcus mutans?

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Correct answer: C — Actinomyces species (particularly A. naeslundii)

Actinomyces species (particularly A. naeslundii/A. viscosus) are strongly implicated in root surface caries alongside S. mutans and Lactobacillus. Root caries develops on exposed cementum/dentin (typically following gingival recession) which has a higher critical pH for demineralisation (~6.2 vs ~5.5 for enamel). Actinomyces colonise root surfaces early and produce acid at relatively high pH levels. The polymicrobial biofilm on root surfaces differs from that on coronal enamel, reflecting the different substrate (collagen in dentin/cementum vs hydroxyapatite in enamel).

Reference: Fejerskov & Kidd – Dental Caries: The Disease and Its Clinical Management, 3rd ed., 2015