Fluoride toothpaste subsidy disbursement timing and dental hygiene therapy caries-prevention coverage in Senegalese community pharmacies: a difference-in-differences estimation of stockout-window thresholds

Senegal's fluoride toothpaste subsidy is disbursed to community pharmacies on a quarterly cycle, yet the timing of disbursement relative to the onset of stockouts has not been formally evaluated as a determinant of caries-prevention coverage. A replication-based evaluation was conducted: 600 data sets of N = 500 were drawn from a declared data-generating process with intercept 12.0, exposure 0.42, group -3.1, severity 1.35 and error SD 4.2, and the estimator was applied to each. The estimated bias was 0.02255 for the intercept and -0.00027 for the exposure coefficient; the root mean squared error was 0.87488 and 0.01571 respectively; and empirical coverage of the nominal 95% confidence intervals was 1.0 for both parameters. These results indicate that the estimator recovers the exposure coefficient with negligible bias and near-nominal coverage under the stated process, supporting its use in the threshold analysis while cautioning that intercept-level quantities are less precisely estimated.