Shern 1976.

Study characteristics
Methods	Study design: 5‐arm RCT (all arms are relevant); placebo controlled Study duration: 2 years (but only 1 year results used)
Participants	562 children analysed at 1* year (available at 1st examination) Participants randomised (N = 614) Age range 6‐13 years Surfaces affected: 2.7 DMFS (data from original sample only) Exposure to other fluoride: none assumed Year study began: in/before 1973 Location: Venezuela Setting of recruitment and treatment: school
Interventions	FG (3 groups) + ptc vs PL (2 groups) + ptc (APF group 1 = 12,300 ppm F, AmF group 2 = 12,500 ppm F, AmF group 3 = 12,500 ppm F) Operator applied, with tray, 5 consecutive applications (every day/week) in 1st year, 3 mg (about 14 drops) applied for 5 min Prior to application = tooth cleaning performed with rotating rubber‐cup with non‐F abrasive paste Postop instruction = refrain from rinsing and eating for 30 min
Outcomes	1‐year* net DMFS increment Reported at 1 and 2 year follow‐ups O‐DMFS MD‐BL‐DMFS Side effects Dropout
Declaration of interest	No information provided.
Source of funding	The study was supported by GABA AG, Basel.
Notes	Clinical (VT) caries assessment by 1 examiner; diagnostic threshold NR; state of tooth eruption included NR; diagnostic errors NR *Intervention applied during 1st year of study only (final 2 years results not considered).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: “...were assigned from classroom rosters at random to one of five groups.” 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: “To assure a double‐blind study, the examiner was not informed about the group assignment of any child or the results of the child’s previous examinations, and the gels were similar in physical characteristics.” Comment: Blind outcome assessment and use of placebo described.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: “To assure a double‐blind study, the examiner was not informed about the group assignment of any child or the results of the child’s previous examinations, and the gels were similar in physical characteristics.” 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: 8.47% in 1 year. Dropout by group: 14/144 FG1, 12/143 FG2, 10/138 FG3, 4/90 PL1, 12/99 PL2. "losses distributed evenly among groups". Reasons for losses: NR Comment: Numbers lost not unduly high for length of follow‐up with almost no differential losses between groups (9.72% FG1, 8.39% FG2, 7.25% FG3, 4.44% PL1, 12.12% PL2). It is unclear if reasons for dropout are acceptable and balanced. Caries data used in analysis pertain to participants present at all examinations.
Selective reporting (reporting bias)	Low risk	Outcomes reported: DMFS increment, reported at 1 and 2 year follow‐ups O‐DMFS, MD‐BL‐DMFS, Side effects. 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 (sample at baseline only): DMFS: 2.80(6.63) FG1, 2.85(4.54) FG2, 2.51(3.41) FG3, 2.46(3.23) PL1, 2.99(4.68) PL2 Comment: Initial caries appears balanced between groups.
Free of contamination/co‐intervention?	Unclear risk	No information provided.