Point-of-Care Caries Risk Screening Integration and Dental Hygiene Referral Yield in Tanzanian Primary Care: An Instrumental-Variable Analysis of Diagnostic Adoption

Tanzania's primary care system has piloted point-of-care caries risk screening (POC-CRS) in selected dispensaries, yet referral yield to dental hygiene services remains uneven across facilities. The instrument is constructed from the interaction of facility distance to the nearest dental training institution and the timing of regional oral health coordinator deployment, which affects adoption but plausibly not referral yield except through adoption. Using the DHS Program indicator 'Percentage receiving injection given by health care provider' (FP_SPUS_W_SPH) across 14 African country surveys from 2021 to 2025 as a calibration benchmark for facility-level care-process capture, the analysis specifies the first-stage and structural equations, derives the bias of naive adoption estimates, and characterises the conditions under which the IV estimand identifies a local average treatment effect for complier facilities. The calibration sample has a mean of 91.964 and a standard deviation of 12.468 (N = 14), with country values ranging from 60.90 in Malawi to 99.70 in Kenya. The framework proposes that IV estimates of POC-CRS effects will exceed naive estimates where adoption concentrates among high-capacity facilities, and it specifies the falsification tests and sensitivity bounds required before the design can be fielded. The contribution is a pre-registration-ready identification strategy for diagnostic adoption research in African dental hygiene, not a completed field estimate.