Task-Shifted Dental Therapy Supervision Ratio and Restorative Treatment Failure Among Malawian Rural Clinics: A Multilevel Analysis of Scope-of-Practice Boundaries

Malawi's rural dental services depend on task-shifted dental therapists working under nominal supervision ratios that were set administratively rather than derived from failure data. Because no clinic-level failure registry exists, the study is framed as a multilevel analytical design specified for a national survey of restorations placed in rural clinics, with the DHS Program indicator 'Knowledge of any method of contraception among married women' (FP_KMET_W_ANY) used as a verified population-level covariate across 38 African countries and 162 country-survey observations from 1986 to 2025 (mean 91.776, SD 11.342, range 57.80 in Chad to 99.90 in Eswatini). The design specifies a two-level logistic model with restorations nested in clinics and clinics nested in districts, and it treats the supervision ratio as a clinic-level exposure whose effect is permitted to vary by procedure class. The contribution is a scope-of-practice boundary framework that distinguishes ratio effects on procedures inside the therapist's autonomous scope from ratio effects on procedures that require delegated authorization. The framework predicts that ratio effects concentrate on delegated procedures, that the population covariate attenuates clinic-level variance only modestly, and that the appropriate policy lever is scope redesign rather than ratio reduction. The paper concludes that supervision ratios are a blunt instrument whose apparent effect is an artefact of scope boundaries, and that Malawi's task-shifting policy should be evaluated against procedure-specific authorization rules rather than a single numeric ratio.