Blinkhorn 1983.

Methods	Stratified random allocation; double‐blind (A); placebo‐controlled; 9% drop out after 3 years (study duration = 3 years). Reasons for attrition described with respective total numbers; no differential group losses.
Participants	567 children analysed at 3 years (available at final examination). Age range at start: 11‐12 years. Surfaces affected at start: 8.4 DMFS. Exposure to other fluoride: no. Year study began: 1972. Location: UK.
Interventions	FR+PLT versus FR+FT versus FT+PLR. FR = NaF 230 ppm F. School mouthrinsing/supervised, daily, for 0.5 min (after toothbrushing with appropriate toothpaste at school). FT = SMFP 1000 ppm F. School toothbrushing/supervised, daily, for 1 min (followed by mouthrinsing with appropriate solution); appropriate toothpaste provided for home use. Abrasive system: IMP (main abrasive).
Outcomes	3yNetDFS increment ‐ (E+U)(CA)cl+(DR)xr. Reported at 3 years follow up. PF‐DFS. MD‐BL‐DFS. MD‐DFS. postMD‐DFS. DMFT (E/U). anterior DMFT. posterior DMFT. DFS (U). Drop out.
Notes	Participants randomized (N = 621). Baseline characteristics (DMFS, DMFT, SAR) 'balanced' (DFS baseline data NR). Clinical (V) caries assessment by one examiner, diagnostic threshold = CA. Radiographic assessment (1 postBW) by one examiner; diagnostic threshold = DR. State of tooth eruption included = E/U. Intra‐examiner reproducibility checks for incremental clinical and radiographic caries data in 10% sample (icc score 0.9).
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Unclear risk	B ‐ Unclear