Silver Diamine Fluoride Arrest Rate and Dental Therapy Retreatment Burden in Ethiopian Health Centres: A Target-Trial Emulation of Lesion-Reactivation Thresholds

Silver diamine fluoride (SDF) arrests cavitated dentine lesions without restorative intervention, but arrest is not permanent and the retreatment burden it generates depends on how reactivation is defined and detected. the present analysis reframes SDF arrest as a threshold problem rather than a fixed success rate, and asks what arrest proportion a health-centre programme must sustain for annual retreatment demand to remain within the dental-therapist workforce available in Ethiopian primary care. Because no primary cohort was assembled, the analysis is a design and operating-characteristics study: a before-after-control-impact (BACI) estimator was evaluated across 2000 replications per design cell for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points, under a declared variance structure with between-cluster SD 6.0, residual SD 4.5 and intraclass correlation 0.64. Power reached 80% at 54 clusters for a 5-percentage-point effect, and minimum detectable effect fell steeply as clusters increased. The results imply that lesion-reactivation thresholds below roughly 5 percentage points cannot be resolved by the cluster counts typical of Ethiopian woreda-level programmes, so retreatment budgets calibrated to finer thresholds will be statistically unverifiable. The contribution is a threshold-based specification of SDF programme monitoring that aligns arrest definitions with the design sensitivity actually attainable.