Chlorhexidine Substantivity — MFDS Part 1 MCQ
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Correct answer: B — 8–12 hours
The correct answer is B. Chlorhexidine is cationic and binds to oral mucosa, acquired dental pellicle and other oral substrates, from which it is gradually released. This retention—substantivity—can persist for approximately 8–12 hours after a mouth rinse; contemporary in-situ research detected chlorhexidine in mucosal and dental pellicles for at least 12 hours. Durations of 30 minutes to 2 hours substantially underestimate its retention and are more typical of less substantive antiseptic effects or formulations. Persistence for 24 hours or longer is not supported after a single routine mouth rinse. Detectable retention does not necessarily imply an unchanged maximal bactericidal effect throughout the whole period.
Reference: Reda B, Hollemeyer K, Trautmann S, Volmer DA, Hannig M. First insights into chlorhexidine retention in the oral cavity after application of different regimens. Clinical Oral Investigations. 2021;25:6109–6118. https://pubmed.ncbi.nlm.nih.gov/33825020/