Koch 1967b.

Methods	Stratified random allocation***; double‐blind (A); placebo‐controlled; 19% drop out after 2 years (study duration = 2 years). Natural losses; any differential group losses not assessable.
Participants	70 children analysed at 2 years (present for entire trial period). Age range at start: 13‐14 years. Surfaces affected at start: 30.1 DFS. Background exposure to fluoride: none reported. Year study began: 1963. Location: Sweden.
Interventions	FT versus PL (NaF group = 1000 ppm F). Home use/unsupervised, twice a day instructed frequency but daily frequency assumed, for 2 min. Abrasive system: methacrylate polymer (acrylic).
Outcomes	2yDFS increment ‐ cl(CA)(E). Reported at 2 years follow up. DFT. O‐DFS. MD‐DFS. BL‐DFS. Annual CAR. Secondary caries.
Notes	Participants randomised (N = 86); numbers by group NR. 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