Dental Therapy Task-Shifting Supervision Ratio and Restorative Treatment Failure Among Mozambican Primary Care Clinics: A Multilevel Analysis of Scope-of-Practice Boundaries

Mozambique's primary oral health system relies on dental therapists working under supervising dentists, yet the ratio at which supervision ceases to protect restorative quality remains unquantified. The model treats supervision as a finite attentional resource distributed across procedures of differing complexity, and derives a failure function in which the marginal protective effect of additional supervisory contact declines as the ratio widens. Three propositions follow: that restorative failure rises non-linearly beyond a ratio of approximately one supervisor to four therapists; that the threshold is lower for multi-surface than for single-surface restorations; and that clinic-level therapist density modifies the individual-level relationship. The contribution is a testable specification linking task-shifting policy to clinical outcomes in resource-constrained settings, together with the identification strategy required to estimate it. Supervision ratios function as scope-of-practice boundaries in practice, not merely as administrative conveniences, and that failure to specify them numerically leaves task-shifting policy without an evidence base.