Bijella 1981.

Study characteristics
Methods	Study design: 4‐arm parallel‐group quasi RCT (only 2 relevant arms used); non‐placebo controlled Study duration: 1.5 years
Participants	320 children analysed at 1.5 years (after exclusions, available at final examination) Participants randomised (N = 401) Age range 7‐10 years Surfaces affected: 6.6 DMFS Exposure to other fluoride: none assumed Year study began: 1979 Location: Brazil Setting of recruitment and treatment: school and school clinic, respectively
Interventions	FG + ptc* versus NT (APF group = 12,300 ppm F) Operator applied, with cotton‐paint tip, 2 ml applied for 4 min, once a year Prior to application = tooth cleaning performed with rotating rubber cup + floss with a non‐F prophy paste Postop instruction = refrain from rinsing, eating, and drinking for 30 min
Outcomes	1.5‐year DMFS increment ‐ (CA)(E) Reported at 1.5 years follow‐up O‐DMFS BL‐DMFS MD‐DMFS DMFT(CA)(E)
Declaration of interest	No information provided.
Source of funding	[PhD Dissertation]. No information provided.
Notes	Clinical (VT) caries assessment by 4 examiners; diagnostic threshold = CA; state of tooth eruption included = E; reversal rate = 2.2% and 0.7% of observed DMFS increment in FG and control groups, respectively. *Prior prophylaxis with non‐F paste carried out in FG group only.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: “Children were initially ordered by the number of permanent teeth present, then by level of DMF, and then, they were, each 4, distributed 'at random', to form each one of the 4 groups designated I, II, III and IV. Each group formed in this way were assigned 'at random' to the treatments (3 groups) and control (1 NT group).” Comment: Method unclear, quasi method likely.
Allocation concealment (selection bias)	High risk	Quote: “Children were initially ordered by the number of permanent teeth present, then by level of DMF, and then, they were grouped, each 4, distributed 'at random', to form each one of the 4 groups designated I, II, III and IV. Each group formed in this way were assigned 'at random' to the treatments (3 groups) and control (1 NT group).” Comment: No concealment of allocation indicated/likely.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: “Group I received no treatment and served as the control group" Comment: No placebo described.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: "The examiners had no knowledge of the children's group assignment, neither was this information available in their records, which were brought for examination at random, without consideration of group assignment .... Each child was re‐examined by the same dentist of previous examination. Author was involved in providing topical applications" “Group I received no treatment and served as the control group" Comment: Blind caries assessment described, but indication that examiner may have been involved in providing treatment AND no placebo used.
Incomplete outcome data (attrition bias) All outcomes	High risk	Overall dropout for length of follow‐up: 81/401 (20.2%) in 1.5 years. Dropout by group: 41/201 (20.4%) FG, 40/200 (20%) NT. Reasons for losses: Exclusions based on 'statistical reasons' (made at random to keep groups of equal size, after 11% 'natural loss'). Comment: Numbers lost were not high for the length of follow‐up, but it is unclear if there were differential losses between groups (since the numbers above were produced after 'statistical' exclusions). It is unclear if all reasons for dropout are acceptable and balanced. Caries data used in analysis pertain to participants present at final examinations, after exclusions were made at random to keep groups balanced in size (not all participants available at follow‐up were actually analysed).
Selective reporting (reporting bias)	Low risk	Outcomes reported: DMFS and DMFT increment ‐ (CA)CL, reported at 1.5 years follow up. ODMFS, MDDMFS, BLDMFS Comment: Trial protocol (thesis) 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 (for sample randomised and final/analysed at 1.5 years): DMFS: 6.7 FG, 6.6 NT DMFT: 4.1 FG, 4 NT Comment: Initial caries appears balanced between groups. Dental age and gender are other characteristics reported and balanced.
Free of contamination/co‐intervention?	Unclear risk	No information provided on inadvertent application of the intervention to people in the control group (contamination), or on possibility of additional treatment given to one of the groups differentially (co‐intervention).