Andlaw 1975.

Methods	Trial design: 2‐armed, double‐blind, placebo‐controlled and stratified RCT Location: UK Number of centres: 3 comprehensive schools (Henbury, Brislington, Withywood) in Bristol, UK Recruitment period: study commenced in 1970
Participants	Inclusion criteria: first‐year intakes at each school Exclusion criteria: not reported Baseline caries: 6.9 DFS (Gp A: 6.85 DFS (SD 4.38); Gp B: 6.97 DFS (SD 4.72)). Baseline characteristics (TAR, DFS, DMFS, DFT, DMFT, ECSI) "balanced" Age at baseline (years): 11 to 12 years (Gp A: 11.72 (SD 0.35); Gp B: 11.70 (SD 0.34)). Baseline characteristic (age) "balanced" Sex: overall: 343 F:397 M (Gp A: 171 F:193 M; Gp B: 172 F:204 M). Evaluated participants reported only Any other details of important prognostic factors: no background exposure to fluoride reported; natural fluoride level of community water supply ranged from 0.07 to 0.14 ppm F Number randomised: 846 (Gp A: 418; Gp B: 428) Number evaluated: 740 at 3 years (present at final assessment. Gp A: 364; Gp B: 376) Attrition: 13% dropout after 3 years. Main reasons for attrition described: moved away, absent at final examination; no differential group losses
Interventions	Comparison: FT versus PL Gp A (n = 418): SMFP 1000 ppm F; Al oxide trihydrate abrasive system; home use/unsupervised, daily frequency assumed Gp B (n = 428): placebo; Al oxide trihydrate abrasive system; home use/unsupervised, daily frequency assumed
Outcomes	Primary: 3‐year net DFS increment ‐ (E + U) (CA) cl + (ER) xr; DMFS; DFT; DMFT; PF‐DMFS; MD‐BL‐DMFS; MD‐DMFS; O‐DMFS; ECSI (at 3 years follow‐up) Secondary: none assessed Assessments irrelevant to this review's scope: oral debris index; gingival index Follow‐up duration: 3 years
Notes	Adverse effects: not reported Funding source: "supported by Gibbs Dental Research" Declarations/conflicts of interest: not reported Data handling by review authors: none Other information of note: clinical (VT) caries assessment by 2 examiners, diagnostic threshold = CA. Radiographic assessment (2 postBW) by 2 examiners, diagnostic threshold = ER. State of tooth eruption included = E/U. Reproducibility ratio was less than 0.22 for intra‐examiner reproducibility of clinical and radiographic caries diagnosis; "significant differences between examiners could not have affected caries increment figures since each examined same children annually"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Following baseline examinations, the children were grouped on the basis of age, sex, previous caries experience and the number of erupted second permanent molars; they were then randomly assigned to either the test or control 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: "Radiographs were examined ...... without reference to the clinical examination data..." "The test dentifrice contained MFP.... The toothpastes were packed in similar but distinguishable tubes. The investigators did not know which of the tubes contained the test paste nor which of the pastes any child was using" Comment: blind outcome assessment and use of placebo described
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Overall dropout for length of follow‐up: 13% in 3 years. Dropout by group: 54/418 FT, 52/428 PL. Reasons for losses: did not like taste of paste (1 from control group), changed school or moved away (63), exclusion due to absence at last examination Comment: numbers lost were not unduly high for the length of follow‐up, with no differential loss between groups. It is unclear if reasons for missing outcome data are acceptable and balanced. Caries data used in analysis pertain to participants present at final examination
Selective reporting (reporting bias)	Low risk	Outcomes reported: DFS increment ‐ (E + U) (CA) cl + (ER) xr, reported at 3 years follow‐up DMFS DFT DMFT PF‐DMFS MD‐BL‐DMFS MD‐DMFS O‐DMFS ECSI 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: 6.30 (4.04) FT, 6.43 (4.31) PL age (years): 11.73 (0.33) FT, 11.69 (0.32) PL TAR: 17.25 (4.35) FT, 17.35 (4.40) PL dental age: 21.75 (4.51) FT, 21.77 (4.47) PL DFT: 4.52 (2.56) FT, 4.42 (2.66) PL DMFT: 5.04 (2.68) FT, 4.96 (2.99) PL DMFS: 8.80 (6.55) FT, 9.10 (7.25) PL ECSI: 12.03 (8.34) FT, 12.41 (8.66) PL Comment: initial caries appears balanced
Free of contamination/co‐intervention?	Low risk	Quote: "The distribution of toothpastes and toothbrushes was the responsibility of two ladies called 'home visitors', whose duties were to visit each home every 5 weeks to supply enough of the appropriate toothpaste for the needs of the whole family.... and maintaining the interest and co‐operation of participants throughout the trial" Comment: there is sufficient indication overall of prevention of contamination/co‐intervention