Window of Infectivity — NDEB AFK MCQ
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Correct answer: E — 19-31 months of age (coinciding with primary molar eruption)
The 'window of infectivity' (Caufield et al., 1993) identifies the period of approximately 19-31 months of age as the time when children are most susceptible to initial colonisation by S. mutans. This coincides with the eruption of the primary molars, which provide the first major tooth surfaces (pit and fissure system, broad proximal contacts) suitable for S. mutans adhesion. S. mutans is transmitted primarily from the mother (vertical transmission via saliva sharing). Delaying maternal-child transmission beyond this window is associated with reduced caries in the child.
Reference: Fejerskov & Kidd – Dental Caries: The Disease and Its Clinical Management, 3rd ed., 2015