Root caries in frail older adults is a persistent clinical problem, and domiciliary fluoride varnish delivered by dental hygienists is a plausible preventive strategy. The unresolved difficulty is not whether varnish works but whether a home-visit schedule can be designed that is both clinically effective and operationally feasible when caregiver availability constrains when visits can occur. the present analysis treats the problem as a design question rather than an observational one. It specifies a target trial in which dental hygiene therapists deliver fluoride varnish to frail older adults in Cape Town at intervals determined by caregiver availability, and it emulates that trial using a before-after-control-impact (BACI) estimator under a declared variance structure. No observational data are used or claimed. The analysis characterises the operating characteristics of the design across cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points, with 2000 replications per design cell. The intraclass correlation is 0.64, between-cluster standard deviation 6.0 and residual standard deviation 4.5. Fifty-two clusters are required to detect a 5 percentage point effect at 80% power. Caregiver availability is not a nuisance covariate but a structural determinant of visit timing, and that scheduling rules which ignore it will bias the estimated effect of varnish delivery. The contribution is a design specification and a power analysis that make the caregiver constraint explicit in the estimand.
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Naledi Kgomotso Molefe (2026) studied this question.
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