Zacherl 1981.

Methods	Stratified random allocation; double‐blind (A); placebo‐controlled; 43% drop out after 3 years (study duration = 3 years). Reasons for attrition described: change of residence, absent on examination day, poor quality of x‐rays; no differential group losses.
Participants	1754 children analysed at 3 years (available at final examination). Age range at start: 6‐13 years (average = 9). Surfaces affected at start: 5.8 DMFS. Background exposure to fluoride: none reported. Year study began: in/before 1977. Location: USA.
Interventions	FT (2 groups) versus PL (SnF2 group = 1000 ppm F, NaF group = 1100 ppm F). Home use/unsupervised, daily frequency assumed. Abrasive system: Ca pyrophosphate in SnF2 and placebo toothpastes, silica in NaF toothpaste.
Outcomes	3yDMFS increment ‐ (CA)cl+(ER)xr. Reported at 1, 2 and 3 years follow ups. DMFT.
Notes	Participants randomised (N = 3093). Baseline characteristics (DMFS, DMFT) 'balanced'. Clinical (VT) caries assessment (FOTI used) by one examiner, diagnostic threshold = CA. Radiographic assessment (postBW) by one examiner; diagnostic threshold = ER. State of tooth eruption included = NR. Intra‐examiner reproducibility checks for incremental clinical and radiographic caries data in 10% sample (icc score 0.9). Reversal rate very low and similar among groups.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear

Drop‐out rate based only on groups relevant to review, on relevant follow ups, unless otherwise stated. Baseline caries experience averaged among relevant study arms, and based on the study sample analysed at the end of study period (final sample), unless otherwise stated. Age range (average age when reported) at the time the study started based on all study participants (or on groups relevant to the review when data were available).
 1stm = first permanent molar; 'A' = classified as double‐blind but participants may not be blind (as a 'PL' was used); Al = aluminium; Alumina = Al oxide trihydrate (Al2O3); AmF = amine fluoride; APF = acidulated phosphate fluoride; Ca = calcium; Ca carbonate = CaCO3; CA = lesions showing loss of enamel continuity that can be recorded clinically (undermined enamel, softened floor/walls) or showing frank cavitation; CAR = caries attack rate; CIR = caries incidence rate; Chlor = chlorhexidine diguclonate; cl = clinical examination; d(e)ft/s = decayed, (extracted) and filled deciduous teeth or surface; dmft/s = decayed, missing (or extracted) and filled deciduous teeth or surface; D(M)FS/T = decayed, (missing ) and filled permanent surfaces or teeth; DR = radiolucency into dentin; E = teeth erupted at baseline; ECSI = Extrapolated Caries Surface Index (assesses caries progression into enamel/dentin/pulp); ER = any radiolucency in enamel/enamel‐dentin junction; F = fluoride; FR = fluoride mouthrinse; FT = fluoride toothpaste; icc = intra‐class correlation coefficient (for inter‐rater reliability); IMP = insoluble Na metaphosphate; M = missing permanent teeth; MD = mesio and distal surfaces; N = numbers; Na = sodium; NaF = sodium fluoride; Na bicarbonate = NaHCO3; NCA = non‐cavitated enamel lesions visible as white spots or discoloured fissures; NR = not reported; NS = not significant; O = occlusal surfaces; PF = pit and fissure surfaces; PL = placebo toothpaste; 'PL' = fluoride‐free toothpaste but not a true placebo (e.g. different in taste or colour from test toothpaste(s)); post BW = posterior bite‐wing x‐ray assessment; ppm F = parts per million of fluoride; ptc = prior tooth‐cleaning performed with or without a non‐fluoride paste; Silica = silicon dioxide (SiO2; SMFP = sodium monofluorophosphate; SnF2 = stannous fluoride; U = teeth unerupted at baseline; VT = visual‐tactile assessment; xr = radiographic examination.