Hodge 1980.

Methods	Trial design: 4‐armed, double‐blind, placebo/active‐controlled and stratified RCT Location: UK Number of centres: 6 schools in North‐West England, UK Recruitment period: study commenced in/before 1976
Participants	Inclusion criteria: not reported Exclusion criteria: not reported Baseline caries: 7.3 DMFS (Gp A: DMFS 6.97 (SD 4.91)/DMFT 4.40 (SD 2.84); Gp B: DMFS 7.81 (SD 5.76)/DMFT 4.82 (SD 3.02); Gp C: DMFS 7.63 (SD 6.23)/DMFT 4.62 (SD 3.12); Gp D: DMFS 6.93 (SD 4.59)/DMFT 4.37 (SD 2.62)). Baseline characteristics (DMFS, DMFT) "balanced" Age at baseline (years): range 11 to 12 years Sex: 391 F:408 M (Gp A: 94 F:100 M; Gp B: 100 F:100 M; Gp C: 96 F:107 M; Gp D: 101 F:101 M) Any other details of important prognostic factors: no background exposure to fluoride reported. Natural fluoride level of community water supply 0.8 ppm F Number randomised: 979 (group numbers not reported) Number evaluated: 799 at 3 years (present at final assessment. Gp A: 194; Gp B: 200; Gp C: 203; Gp D: 202) Attrition: 18% dropout after 3 years (study duration = 3 years). Reasons for attrition described with respective total numbers: 158 left school, 14 withdrawn by own choice, 8 lack of co‐operation; any differential group losses not assessable
Interventions	Comparison: FT (3 groups) versus PL Gp A (n = 194 evaluated): SMFP 1000 ppm F; alumina abrasive system; school use/supervised, daily, for 1 min (appropriate toothpastes also provided for home use) Gp B (n = 200 evaluated): SMFP‐NaF 1450 ppm F; alumina abrasive system; school use/supervised, daily, for 1 min (appropriate toothpastes also provided for home use) Gp C (n = 203 evaluated): SMFP‐NaF 1450 ppm F; dicalcium phosphate abrasive system; school use/supervised, daily, for 1 min (appropriate toothpastes also provided for home use) Gp D (n = 202 evaluated): placebo; abrasive system: alumina abrasive system; school use/supervised, daily, for 1 min (appropriate toothpastes also provided for home use)
Outcomes	Primary: 3‐year net DFS increment ‐ (E) (CA) cl + (DR) xr; DMFT (at 3 years) Secondary: not assessed Assessments irrelevant to this review's scope: compliance Follow‐up duration: 3 years
Notes	Adverse effects: not reported Funding source: supported by grant from manufacturer, Colgate Palmolive Ltd Declarations/conflicts of interest: not reported Data handling by review authors: Gps B and C (1450 ppm F groups) pooled in analyses 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 = DR. Reproducibility checks done in 10% sample clinically and radiographically (ICC of incremental data between 0.92 and 0.97)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Following the initial baseline examination, subjects were stratified according to school and sex, and randomly assigned to 1 of 4 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	Quote: "The trial was double‐blind, neither the subjects nor the examiner knew who was receiving test or control products. The test and control dentifrices were indistinguishable in taste and appearance" 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: 18.4% (180/979) in 3 years. Dropout by group: not reported. Reasons for losses: changing school (184), moving away, withdrawal from study (14), exclusion due to lack of co‐operation (7) Comment: numbers lost were not unduly high for the 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 analysis pertain to participants present at final examination
Selective reporting (reporting bias)	Low risk	Outcomes reported: DFS increment ‐ (E) (CA) cl + (DR) xr, reported at 3 years follow‐up DMFT 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: DMFT: 4.82 (3.02) FT 1, 4.62 (3.12) FT 2, 4.40 (2.84) FT 3, 4.37 (2.62) PL DMFS: 7.81 (5.76) FT 1, 7.63 (6.23) FT 2, 6.97 (4.91) FT 3, 6.93 (4.59) PL SAR: 90.61 (20.13) FT 1, 88.05 (22.00) FT 2, 90.00 (22.95) FT 3, 87.09 (22.36) PL Comment: initial caries appears balanced
Free of contamination/co‐intervention?	Low risk	Quote: "Dentifrices were used daily in school, either immediately following morning or afternoon registration, the children being under the care of brushing supervisors" Comment: there is sufficient indication overall of prevention of contamination/co‐intervention