Kinkel 1972.

Methods	Random allocation; double‐blind (A); placebo‐controlled; 25% drop‐out rate after 3 years (study duration = 7 years). Reasons for drop out not described; any differential group losses not assessable.
Participants	699 children analysed at 3 years. Average age at start: 10 years. Surfaces affected at start: 2.2 DMFS. Background exposure to fluoride: data not available. Year study began: in/before 1969. Location: Switzerland.
Interventions	FT versus PL (SMFP group F concentration NR). Home use/unsupervised, daily frequency assumed. Abrasive system: NR.
Outcomes	3yDMFS increment ‐ (CA)cl+(DR)xr. Reported at 1, 2, 3, 4, 5 and 7 years follow ups.
Notes	Participants randomised (N = 927); numbers by group NR. Baseline characteristics (DMFS) 'balanced'. Clinical (V) caries assessment; diagnostic threshold = CA and NCA; state of tooth eruption included NR. Radiographic assessment (2 postBW); diagnostic threshold = DR and ER.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear