Abrams 1980.

Methods	Stratified random allocation; double‐blind (A); placebo‐controlled; 48% drop out after 3 years (study duration = 3 years). Reasons for high drop out described: change of residence, absenteeism, non‐adherence to study protocol; no differential group losses.
Participants	1141 children analysed at 3 years (available at final examination). Age range at start: 5‐12 years. Surfaces affected at start: 3.2 DFS. Background exposure to fluoride: none reported. Year study began: in/before 1976. Location: USA.
Interventions	FT (2 groups) versus PL (both SnF2 groups = 1000 ppm F). Home use/unsupervised, daily frequency assumed. Abrasive system: silica gel in one SnF2 and placebo toothpaste, Ca pyrophosphate in the other SnF2 toothpaste.
Outcomes	3yNetDFS increment ‐ (E+U) (CA)cl+(ER)xr. Reported at 1, 2 and 3 years follow ups. DMFT. DMFS. DFT. MD‐DFS. DFT rate. DFS rate.
Notes	Participants randomised (N = 2210). Baseline characteristics (DFS) 'balanced' . Clinical (VT) caries assessment by two examiners, diagnostic threshold = CA. Radiographic assessment (postBW) by two examiners; diagnostic threshold = ER. State of tooth eruption included = E/U. Intra‐ and inter‐examiner reproducibility of clinical caries diagnosis (DFS) assessed annually by duplicate examination of 10% random sample (% of times diagnosis replicated in all 3 examinations ranged 42‐97% and 77‐ 92% for both examiners and for each respectively).
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear