Held 1968b.

Methods	Stratified random allocation; double‐blind (A); placebo‐controlled; 62% drop out after 2 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	32 children analysed at 2* years (available at final examination). Average age at start: 15 years. Surfaces affected at start: 10.2 DMFS. Background exposure to fluoride: data not available for fluoridation status of site. Year study began: 1961. Location: France.
Interventions	FT versus PL (NaF group = 500 ppm F). Institution use/supervised, twice a day. Abrasive system: not clearly specified (silica used).
Outcomes	2y*DMFS increment ‐ (E) cl. Reported at 2 and 3 years follow ups. DMFT. Annual CAR.
Notes	Participants randomised (N = 85). 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. *Results for 3 years follow up not considered due to very high drop out rate.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear