Segal 1967.

Methods	Stratified random allocation; double‐blind (A); placebo‐controlled; 23% drop out after 2 years (study duration = 2 years). Reasons for attrition NR; differential group losses.
Participants	648 children analysed at 2 years (available at final examination). Age range at start: 7‐12 years. Surfaces affected at start: NR. Background exposure to fluoride: none reported. Year study began: in/before 1964. Location: USA.
Interventions	FT versus PL (SnF2 group = 1000 ppm F). School use/supervised, daily, (appropriate toothpastes also provided for home use). Abrasive system: IMP (mainly).
Outcomes	2yDFS increment ‐ (CA)cl+xr. Reported at 1 and 2 years follow ups. DFS (U).
Notes	Participants randomised (N = 845). Baseline characteristics (SAR) 'balanced'. Clinical (VT) caries assessment by two examiners, diagnostic threshold = CA. Radiographic assessment as a supplementary aid; diagnostic threshold = NR. State of tooth eruption included E/U. Inter‐ and intra‐examiner reproducibility checks done.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear