Task-Sharing Supervision Intensity and Dental Therapy Restorative Error Rates in Zambian Health Centres: A Multilevel Analysis of Clinical Governance Thresholds

Zambia's dental therapy cadre performs the majority of restorative care in rural and peri-urban health centres, yet the supervisory arrangements under which that care is delivered remain poorly characterised. Because no primary clinical audit data were available for this analysis, the study is framed as a methodological and conceptual contribution: it specifies a multilevel modelling strategy for supervision-error relationships, derives the governance thresholds at which supervision ceases to yield marginal error reduction, and illustrates the approach using the DHS Program's published standard errors for neonatal mortality rate (5 year periods) across 38 African countries between 1986 and 2025 (168 country-survey observations; mean 2.779; SD 0.959). The analysis treats these published standard errors as a proxy for measurement instability in health-system indicators, demonstrating how multilevel variance decomposition can distinguish between supervision effects that operate at the therapist level and those that operate at the facility level. Supervision intensity exhibits a threshold structure: below a critical density of supervisory contact, marginal increases in supervision produce substantial error reduction, but above that threshold the marginal return diminishes sharply. This threshold logic has direct implications for how Zambian health authorities allocate scarce dentist time across district health centres, and for how clinical governance indicators should be specified in task-sharing programmes more broadly.