Peterson 1979.

Methods	Trial design: 3‐armed, double‐blind, placebo‐controlled, stratified RCT Location: USA Number of centres: not reported. Parochial schools in Bismarck and Fargo, North Dakota Recruitment period: study began 1971
Participants	Inclusion criteria: not reported Exclusion criteria: not reported Baseline caries: 2.9 DFS (Gp A: 3.04 (SD 3.50); Gp B: 2.85 (SD 2.92); Gp C: 2.69 (SD 2.66)). Baseline characteristics (DFS, MD‐DFS, DFT, SAR, TAR) "balanced" (evaluated participants only) Age at baseline (years): range 8 to 12 years, mean 10 years (Gp A: 123.88 months (SD 13.01); Gp B: 124.84 months (SD 11.94); Gp C: 124.64 months (SD 12.11)) (evaluated participants only) Sex: not reported Any other details of important prognostic factors: background exposure to fluoride: community water supply fluoridated 1.2 ppm F Number randomised: 950 (group distribution not reported) Number evaluated: 712 at 2.5 years (present for all examinations) (Gp A: 237; Gp B: 230; Gp C: 245) Attrition: 25% dropout after 2.5 years (study duration = 2.5 years). Natural losses; exclusions based on presence in all follow‐up examinations; any differential group losses not assessable
Interventions	Comparison: FT (2 groups) versus PL Gp A (n = evaluated 237): SMFP 1000 ppm F; abrasive system: Ca carbonate; school use/supervised, daily (appropriate toothpastes also provided for home use) Gp B (n = evaluated 230): SMFP 1000 ppm F; abrasive system: IMP; school use/supervised, daily (appropriate toothpastes also provided for home use) Gp C (n = evaluated 245): placebo; abrasive system: Ca carbonate; school use/supervised, daily (appropriate toothpastes also provided for home use)
Outcomes	Primary: 2.5‐year DFS increment ‐ cl + xr; DMFT; MD‐DFS (at 2.5 years) Secondary: none assessed Assessments irrelevant to this review's scope: n/a Follow‐up duration: 2.5 years
Notes	Adverse effects: not reported Funding source: grant from manufacturer, Beecham Inc Declarations/conflicts of interest: not reported Data handling by review authors: groups A + B combined versus C in analysis Other information of note: clinical (VT) caries assessment (FOTI used) by 1 examiner, diagnostic threshold = CA; state of tooth eruption included not reported; radiographic assessment (postBW) by 1 examiner, diagnostic threshold = ER. Diagnostic errors not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "The children were then stratified by age and sex and assigned at random to 1 of 3 dentifrice groups" 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: "Except for the absence of NaMFP, this placebo formulation was identical to that of experimental dentifrice" and "The double blind technique was used, neither the examiner nor the subjects knowing to which dentifrice group they had been assigned" Comment: blinding outcome assessment and use of placebo described
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Overall dropout for length of follow‐up: 25.1% 238/950 in 2.5 years (all groups). Dropout by group: not reported. Reasons for losses: mainly due to moving from the area, and exclusion based on presence at all examinations Comment: numbers lost are not unduly high for length of follow‐up. It is unclear if there were any differential losses, and if reasons for missing outcome data are acceptable and balanced. Caries data used in the analysis pertain to participants present for all examinations
Selective reporting (reporting bias)	Low risk	Outcomes reported: DFS increment ‐ cl + xr, reported at 2.5 years follow‐up DMFT MD‐DFS 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: 3.04 (3.50) FT 1; 2.85 (2.92) FT 2; 2.69 (2.66) PL age (months): 123.88 (13.01) FT 1; 124 (11.94) FT 2; 124.64 (12.11) PL TAR: 14.49 (5.10) FT 1; 15.16 (5.35) FT 2; 14.84 (5.24) PL DFT: 2.23 (2.16) FT 1; 2.06 (1.71) FT 2; 2.05 (1.70) PL SAR: 79.73 (26.22) FT 1; 83.78 (27.28) FT 2; 81.53 (26.37) PL Comment: initial caries appears balanced
Free of contamination/co‐intervention?	Low risk	Quote: "All subjects periodically received toothbrushes and dentifrices individually labelled for school and home use" Comment: there is sufficient indication overall of prevention of contamination/co‐intervention