Dental hygiene therapy scope-of-practice variation and preventive service intensity in Nigerian primary care clinics: a border-discontinuity analysis of regulatory boundaries

Regulatory boundaries for dental hygiene therapy in Nigeria are set at the state level, yet the consequences of this jurisdictional patchwork for preventive service delivery remain unexamined. The framework treats state borders as discontinuities in the regulatory environment and proposes that clinics located near borders provide a natural comparison for estimating the effect of scope-of-practice rules on service provision. Using the DHS Program indicator 'Percentage receiving injection given by health care provider' (FP_SPUS_W_SPH) for 14 African countries from 2021 to 2025, the analysis establishes a regional benchmark for preventive service delivery against which Nigerian state-level variation can be assessed. The 14 country-survey observations yielded a mean of 91.964 (SD = 12.468), with values ranging from 60.90 in Malawi to 99.70 in Kenya. These figures indicate substantial cross-national heterogeneity in the delivery of basic preventive services, consistent with the hypothesis that regulatory and health-system factors shape service intensity. The analysis is conceptual and methodological; no primary data were collected. The framework provides a basis for future empirical work using clinic-level data from Nigerian states.