Horowitz 1966.

Methods	Quasi‐random allocation; double‐blind (A); placebo‐controlled; 40% drop‐out rate after 3 years (study duration = 3 years). Natural losses; no differential group losses.
Participants	638 children analysed at 3 years (available at final examination). Age range at start: 6‐10 years. Surfaces affected at start: 2.08 DMFS. Background exposure to fluoride: none reported. Year study began: 1961. Location: USA.
Interventions	FT versus PL ** (SnF2 group = 1000 ppm F). Home use/unsupervised, daily frequency assumed. Abrasive system: Ca pyrophosphate.
Outcomes	3yNetDMFS increment ‐ (E+U) (CA)cl. Reported at 1, 2, and 3 years follow ups. DMFT.
Notes	Participants randomised (N = 1059). Baseline characteristics (DMFS, DMFT, TAR) 'balanced'. Clinical (VT) caries assessment by three examiners; diagnostic threshold = CA; state of tooth eruption included = E/U. Reversals were small in both groups (about 3% of DMFS increments) and equally common (NS different). ** Only relevant comparison (others were not randomised/quasi‐randomized)
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	High risk	C ‐ Inadequate