Zacherl 1972a.

Methods	Stratified random allocation; double‐blind (A); placebo‐controlled; 36% drop out after 1.7 years (study duration = 1.7 years). Reasons for high drop out NR; exclusions based on presence in both examinations; no differential group losses.
Participants	894 children analysed at 1.7 years (present for both follow up examinations). Age range at start: 7‐14 years (average = 9). Surfaces affected at start: 7.3 DMFS. Background exposure to fluoride: water. Year study began: in/before 1969. Location: Canada.
Interventions	FT (4 groups) versus PL (SnF2 group, NaF group, SMFP group, APF group = 1000 ppm F each). Home use/unsupervised, daily frequency assumed. Abrasive system: Ca pyrophosphate in all toothpastes.
Outcomes	1.7yDMFS increment ‐ cl+xr. Reported at 1 and 1.7 years follow ups. DMFT.
Notes	Participants randomised (N = 1405). 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