Zacherl 1972.

Methods	Stratified random allocation; double‐blind (A); placebo‐controlled; 34% drop out after 2 years (study duration = 2 years). Reasons for attrition NR; no differential group losses.
Participants	447 children analysed at 2 years (available at final examination). Age range at start: 6‐15 years (average = 10). Surfaces affected at start: 11.7 DMFS. Background exposure to fluoride: none reported. Year study began: in/before 1969. Location: Canada.
Interventions	FT versus PL (SnF2 group = 1000 ppm F). Home use/unsupervised, daily frequency assumed. Abrasive system: Ca pyrophosphate in SnF2 toothpaste, placebo toothpaste abrasive NR.
Outcomes	2yDMFS increment ‐ cl+xr. Reported at 1 and 2 years follow ups. DMFT.
Notes	Participants randomised (N = 677). Baseline characteristics (age, gender, DMFS, DMFT) 'balanced'. Clinical (VT) caries assessment by one examiner, diagnostic threshold = NR. Radiographic assessment (5‐10 BW) by one examiner; diagnostic threshold = NR. State of tooth eruption included = NR. Diagnostic errors NR.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear