Mainwaring 1978.

Study characteristics
Methods	Study design: 5‐arm parallel‐group RCT (only 2 relevant arms used), placebo controlled Study duration: 3 years
Participants	631 children analysed at 3 years (available at final examination) Participants randomised (numbers, for 2 relevant groups, NR) Age range 11‐12 years Surfaces affected: 7.9 DFS Exposure to other fluoride: no Year study began: in/before 1974 Location: UK Setting of recruitment and treatment: school and clinic
Interventions	FG + ptc versus PL + ptc (APF group = 12,300 ppm F) Operator applied, with tray, twice a year, applied for 4 min Prior to application = tooth cleaning of stained plaque (with disclosing tablets) performed with toothbrush with a non‐F paste Postop instruction = no information provided
Outcomes	3‐year Net/Crude DFS increment ‐ (CA)(E)CL + (ER)XR Reported at 3 years follow‐up PF‐DFS CL postMD‐DFS XR DFS (U) CL + XR CIR
Declaration of interest	No information provided.
Source of funding	The study was supported by a grant from Beecham Group Ltd (SmithKline Beecham merged with Glaxo Wellcome to become GlaxoSmithKline).
Notes	Clinical (VT) caries assessment by 1 examiner; diagnostic threshold = CA; state of tooth eruption included = E. Radiographic assessment (2 postBW) by 1 examiner; diagnostic threshold = ER. Intra‐examiner reproducibility checks for DFS in 10% sample (ICC for VT/XR over 0.95); error variance less than 5% of total variance; reversal rate less than 4% of observed DFS increment in all groups.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: “Participants were stratified according to age, sex and then randomly assigned to one of the treatment groups; children from the same family were assigned to the same group.” Comment: Not enough information provided.
Allocation concealment (selection bias)	Unclear risk	No information provided.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: “The study was of double‐blind design, neither examiner nor participants knowing the identity of the treatment group to which the subjects had been allocated” “... control group had applications of fluoride free gel.” Comment: Use of placebo described.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: “The study was of double‐blind design, neither examiner nor participants knowing the identity of the treatment group to which the subjects had been allocated” “... control group had applications of fluoride free gel.” 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% in 3 years (for all 5 groups combined). Dropout by group: NR. Reasons for losses: NR Comment: Numbers lost were not unduly high given length of follow‐up, but any differential loss between groups was not assessable. It is unclear if reasons for dropout are acceptable and balanced. Caries data used in the analysis pertain to participants who completed the study.
Selective reporting (reporting bias)	Low risk	Outcomes reported: DFS increment ‐ (E)(CA)CL + (ER)XR, reported at 3 years follow‐up PF‐DFS postMD‐DFS Caries incidence rate 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: 8.19(6.01) FG, 7.59(5.56) PL Comment: Initial caries appears balanced between groups. Age and SAR also reported, and balanced.
Free of contamination/co‐intervention?	Unclear risk	No information provided.