Peterson 1967.

Methods	Stratified random allocation; double‐blind ('A'); placebo‐controlled; 16% drop out after 2 years (study duration = 3 years). Reasons for attrition not described; any differential group losses not assessable.
Participants	954 children analysed at 2 years (available at this examination). Age range at start: 9‐15 years. Surfaces affected at start: 14.3 DMFS. Background exposure to fluoride: data not available for fluoridation status of site. Year study began: in/before 1964. Location: USA.
Interventions	FT (2 groups) versus 'PL' (SnF2 group = 1000 ppm F, APF group = 1000 ppm F). Home use/unsupervised, daily frequency assumed. Abrasive system: Ca pyrophosphate in SnF2 toothpaste, IMP in APF toothpaste, control toothpaste abrasive NR.
Outcomes	2y*DMFS increment ‐ cl+xr. Reported at 1, 2 and 3 years follow ups. DMFT. O‐DMFS. BL‐DMFS. MD‐DMFS.
Notes	Participants randomised (N = 1136); numbers by group NR. Baseline characteristics (DMFS, DMFT, dental age) 'balanced'. Clinical (VT) caries assessment by one examiner; diagnostic threshold NR; state of tooth eruption included NR; radiographic assessment (3 BW) by one examiner; diagnostic threshold NR. Diagnostic errors NR. *Results for 3 years follow up not considered (not fully reported).
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Low risk	A ‐ Adequate