Postpartum Dental Hygiene Visit Timing and Early Childhood Caries Incidence in Nigerian Mother-Infant Pairs: A Target-Trial Emulation of Postnatal Care Windows

The postpartum period offers a narrow window in which a mother's dental hygiene visit can influence both her own oral health and her infant's early caries risk, yet the timing of that visit is rarely treated as a modifiable exposure in caries epidemiology. No observational data are used or claimed. Under a declared variance structure with between-cluster SD = 6.0, residual SD = 4.5 and intraclass correlation = 0.64, power was estimated across 2000 design cells spanning cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The design achieves 80% power at 54 clusters for a 5-percentage-point effect. The framework reframes postnatal dental hygiene timing as a sustained-exposure contrast rather than a single-visit event, and it specifies the cluster counts at which a Nigerian postnatal-care evaluation would be adequately powered. The contribution is methodological: it supplies the design parameters and the estimand definition that a future field evaluation would need, and it identifies the conditions under which the before-after-control-impact estimator recovers the target quantity.