Slack 1971.

Methods	Random allocation; double‐blind ('A'); placebo‐controlled; 33% drop‐out rate after 3 years (study duration = 3 years). Main reasons for drop out: moved away, left school, away on examination day, disliked toothpaste taste, brown staining of teeth; no differential group losses.
Participants	1110 children analysed at 3 years (available at final examination). Age range at start: 11‐12 years. Surfaces affected at start: 11.6 DMFS. Background exposure to fluoride: none reported. Year study began: 1965. Location: UK.
Interventions	FT (3 groups) versus 'PL' (Both SnF2 groups = 1000 ppm F, APF group = 1000 ppm F). Home use/unsupervised, daily frequency assumed. Abrasive system: IMP in one SnF2 toothpaste and in APF toothpaste, dicalcium pyrophosphate in another SnF2 toothpaste; control toothpaste abrasive NR.
Outcomes	3yCrudeDMFS increment ‐ (CA)cl+(ER)xr. Reported at 3 years follow up.
Notes	Participants randomised (N = 1665). Baseline characteristics (age, gender, DMFS, previous F toothpaste use) 'balanced'. Clinical (VT) caries assessment by one examiner; diagnostic threshold = CA; state of tooth eruption included = NR. Radiographic assessment (2 postBW) by one examiner; diagnostic threshold = ER. Consistency of clinical diagnosis revealed by 10% sample checks at each examination.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear