Jackson 1967.

Methods	Quasi‐random allocation; double‐blind (A); placebo‐controlled; 12% drop‐out rate after 3 years (study duration = 3 years). Natural losses; no differential group losses.
Participants	871 children analysed at 3 years (available at final examination). Age range at start: 11‐12 years. Surfaces affected at start: 8.7 DMFS. Background exposure to fluoride: none reported. Year study began: 1962. Location: UK.
Interventions	FT versus PL (SnF2 group = 1000 ppm F). Home use/unsupervised, daily frequency assumed. Abrasive system: dicalcium pyrophosphate.
Outcomes	3yDMFS increment ‐ (E+U)(CA)cl. Reported at 3 years follow up. DMFT. Proportion of caries‐free teeth/surfaces (by tooth type/ surface type) which developed caries. Proportion of children who complained of tooth staining.
Notes	Participants randomised (N = 986). Baseline characteristics (age, DMFS, DMFT, TAR, level of treatment, staining) 'balanced'. Clinical (VT) caries assessment by one examiner; diagnostic threshold = CA; state of tooth eruption included = E/U. Consistency of clinical diagnosis maintained by re‐examination of 10% sample and calibration checks made against reserve examiner.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	High risk	C ‐ Inadequate