Held 1968a.

Methods	Stratified random allocation; double‐blind (A); placebo‐controlled; 64% drop out after 3 years (study duration = 3 years). Reasons for high drop out due to age range at which many leave the institutions; no differential group losses.
Participants	36 children analysed at 3 years (available at final examination). Age range at start: 15‐16 years. Surfaces affected at start: 9.6 DMFS. Background exposure to fluoride: data not available for fluoridation status of site. Year study began: 1961. Location: France.
Interventions	FT versus PL (NaF‐SnF2 group = 1000 ppm F). Institution use/supervised, twice a day. Abrasive system: not clearly specified (silica used).
Outcomes	3yDMFS increment ‐ (E) cl. Reported at 3 years follow up. DMFT. Annual CAR.
Notes	Participants randomised (N = 101). Baseline characteristics (DMFS, DMFT) not balanced. Clinical (VT) caries assessment by one examiner; diagnostic threshold NR; state of tooth eruption included = E. Intra‐examiner reproducibility checks done.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear