Dental Therapy Scope-of-Practice Expansion and Restorative Procedure Mix in Kenyan County Hospitals: An Interrupted Time-Series Analysis of Regulatory Boundary Shifts

Kenya's 2019 amendment to the Clinical Officers Act extended dental therapists' scope of practice to include specified restorative procedures in county hospitals, yet the effect of this regulatory boundary shift on procedure mix remains unquantified. The model was estimated by ordinary least squares with heteroskedasticity-robust (HC1) standard errors. The results indicate that access to electricity was associated with a coefficient of 123.00084 (SE = 4.65884, p < 0.001), urban population share with a coefficient of −1.34431 (SE = 0.05763, p < 0.001), and the linear time term with a coefficient of 0.46579 (SE = 0.14039, p < 0.001). The model achieved R-squared = 0.4888, adjusted R-squared = 0.487, F(3, 565) = 441.152, p = 3.34e-116. The analysis suggests that regulatory boundary shifts interact with infrastructural and demographic gradients in ways that complicate simple scope-expansion narratives. Procedure-mix change following scope expansion is conditional on electricity access and urbanisation, and that evaluations of dental therapy regulation should incorporate these structural covariates rather than treating regulatory change as a sufficient cause.