Reed 1973.

Methods	Stratified random allocation; double‐blind (A); placebo‐controlled; 28% drop out after 2 years (study duration = 2 years). Reasons for attrition not described; no differential group losses.
Participants	1525 children analysed at 2 years (available at final examination). Age range at start: 6‐13 years (average = 9). Surfaces affected at start: 3.3 DMFS. Background exposure to fluoride: none reported. Year study began: in/before 1970. Location: USA.
Interventions	FT (3 groups) versus PL (NaF groups = 1000 ppm F, 500 ppm F, 250 ppm F). Home use/unsupervised, daily frequency assumed. Abrasive system: Ca pyrophosphate.
Outcomes	2yDMFS increment ‐ cl+xr. Reported at 1 and 2 years follow ups. DMFT.
Notes	Participants randomised (N = 2104). Baseline characteristics (age, gender, DMFS, DMFT) 'balanced' . Clinical (VT) caries assessment by one examiner; diagnostic threshold NR; state of tooth eruption included NR. Radiographic assessment (up to 7 BW) by one examiner; diagnostic threshold NR. Diagnostic errors NR.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear