Koch 1967c.

Methods	Stratified random allocation***; double‐blind (A); placebo‐controlled; 19% drop out after 3 years (study duration = 3 years). Natural losses; no differential group losses.
Participants	255 children analysed at 3 years (present for entire trial period). Age range at start: 7‐10 years. Surfaces affected at start: 7.9 DFS. Background exposure to fluoride: none reported. Year study began: 1962. Location: Sweden.
Interventions	FT versus PL (NaF group = 1000 ppm F). School clinic/supervised, 3 times a year, 1g applied for 2 min (no provision of any toothpaste reported for home use). Abrasive system: methacrylate polymer (acrylic).
Outcomes	3yDFS increment ‐ cl(CA)(E). Reported at 1 and 3 years follow ups. DFT. Annual CAR. Secondary caries.
Notes	Participants randomised (N = 316). Baseline characteristics (FS, FT, SAR, TAR) 'balanced'. Clinical (VT) caries assessment by one examiner; diagnostic threshold = CA; radiographic assessment (2 postBW) used as an aid but not reported; state of tooth eruption included = E. Diagnostic errors NR. *** Allocation concealment considered adequate by consensus.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Low risk	A ‐ Adequate