Slack 1967a.

Methods	Trial design: 2‐armed, double‐blind, placebo‐controlled RCT Location: UK Number of centres: 18 'educationally selective' secondary schools (assuming high socio‐economic status?) across Essex, UK Recruitment period: study began 1962
Participants	Inclusion criteria: not reported Exclusion criteria: not reported Baseline caries: 7 DFS (Gp A: 7.18 DFS (SE 0.208); Gp B: 6.76 DFS (SE 0.190)). Baseline characteristics (DFS, DFT, DMFS, DMFT, TAR) "balanced" Age at baseline (years): range 11 to 12 years, mean 11.7 years (Gp A: 11 years 7.3 months (SE 0.152 months); Gp B: 11 years 8.2 months (SE 0.169 months)). Baseline characteristics (age, dental age) "balanced" Sex: 961 F:0 M Any other details of important prognostic factors: background exposure to fluoride: none reported Number randomised: 961 (Gp A: 479; Gp B: 482) Number evaluated: 757 at 3 years, all female (present for all examinations) (Gp A: 376; Gp B: 381) Attrition: 21% dropout rate after 3 years (study duration = 3 years). Reasons for dropout described with numbers: left school, moved away, staining of teeth, on parents request; exclusions based on presence in all follow‐up examinations; no differential group losses
Interventions	Comparison: FT versus PL Gp A (n = 376): SnF2 1000 ppm F; abrasive system: dicalcium pyrophosphate; home use/unsupervised, daily frequency assumed Gp B (n = 381): placebo; abrasive system: dicalcium pyrophosphate; home use/unsupervised, daily frequency assumed
Outcomes	Primary: 3‐year DFS increment ‐ (E) (CA) cl; posterior MD‐DFS; DFT; DMFS; DMFT (at 1, 2, 3 years) Secondary: proportion of children with tooth staining (at 1, 2, 3 years) Assessments irrelevant to this review's scope: soft tissues; dental cleanliness Follow‐up duration: 3 years
Notes	Adverse effects: stains (all stains at 3 years: percentage of each group. Gp A: 42%; Gp B: 16%). Reasons for losses: staining: Gp A n = 2; Gp B n = 0 Funding source: Procter & Gamble Declarations/conflicts of interest: institutional affiliations only Data handling by review authors: n/a Other information of note: clinical (VT) caries assessment by 1 examiner, diagnostic threshold = CA; state of tooth eruption included = E/U. Radiographic assessment (2 postBW) by 1 examiner, diagnostic threshold = ER. 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
Random sequence generation (selection bias)	Unclear risk	Quote: "These girls were randomly allocated within the 18 schools to either the control or study group" Comment: not enough information provided
Allocation concealment (selection bias)	Unclear risk	No information provided
Blinding (performance bias and detection bias) All outcomes	Low risk	Quotes: "The films from all were read at the end of the trial by one examiner, and charted seperate from the clinical examination data. The examiner did not know to which group the films belonged" and "The dentifrices were wrapped in non‐proprietary wrapping and package identified by the manufacturer's code" Comment: blind outcome assessment and use of placebo described
Incomplete outcome data (attrition bias) All outcomes	Low risk	Overall dropout for length of follow‐up: 21% in 3 years. Dropout by group: 103/479 FT, 101/482 PL. Reasons for losses: staining: 2 FT, 0 PL; moved away: 35 FT, 32 PL; changed school: 2 FT, 3 PL; parents' request: 7 FT, 3 PL; exclusion based on presence at all examinations: 57 FT, 63 PL Comment: numbers lost were not unduly high given length of follow‐up with no differential losses between groups. Reasons for the missing outcome data are acceptable and balanced, except for staining, which although related to the intervention, did not affect outcome (very small loss causing no real imbalance). Caries data used in the analysis pertain to participants present at all examinations
Selective reporting (reporting bias)	Low risk	Outcomes reported: DFS increment ‐ (E) (CA) cl, reported at 1, 2 and 3 years follow‐ups DFT DMFS DMFT posterior MD‐DFS proportion of children with tooth staining Comment: trial protocol not available. All pre‐specified outcomes (in Methods) were reported and were reported in the pre‐specified way
Baseline characteristics balanced?	Low risk	Prognostic factors reported: DFS: 7.18 FT, 6.76 PL DFT: 4.90 FT, 4.75 PL DMFS: 9.23 FT, 9.23 PL DMFT: 5.31 FT, 5.24 PL age: 12 FT, 12 PL dental age: 23.98 FT, 23.62 PL TAR: 19.06 FT, 18.87 PL Comment: initial caries appears balanced
Free of contamination/co‐intervention?	Low risk	Quote: "To aid co‐operation and the opportunity for personal contact, two home visitors were appointed to deliver the products personally. The toothpastes were delivered to the homes of the subjects in quantities sufficient to provide a constant supply for all members of the household" Comment: there is sufficient indication overall of prevention of contamination/co‐intervention