Marthaler 1970a.

Study characteristics
Methods	Study design: 4‐arm parallel‐group RCT (only 2 relevant arms used), placebo controlled Study duration: 4 years (but only 2 years results used)
Participants	41 children analysed at 2* years (present for all examinations) Participants randomised (numbers for relevant groups NR) Age range 7‐9 years Surfaces affected: 2.5 DFS Exposure to other fluoride: salt Year study began: 1966 Location: Switzerland Setting of recruitment and treatment: school
Interventions	FG vs PL (AmF/NaF group = 12,500 ppm F) Self applied under supervision, with toothbrush, 22 times a year, 1 g applied for 6 min Prior to application = no tooth cleaning performed Postop instruction = no information provided
Outcomes	2‐year* net DFS increment ‐ (NCA/CA)CL + (DR/ER)XR Reported at 2 and 4 year follow‐ups 1stmPF‐DFS (CA) CL 1stmMD‐DFS (DR) XR
Declaration of interest	No information provided.
Source of funding	The study was supported by GABA AG, Basel
Notes	Clinical (V) caries assessment by 2 examiners; diagnostic threshold = CA and NCA; state of tooth eruption included NR. Radiographic assessment (2 postBW) by 2 examiners; diagnostic threshold = DR and ER; partial recording. 'Sufficient agreement of examiners known from earlier work' (quote from the report) *FG replaced by F solution after 2 years (final 4 years results not considered)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “Children were paired according to their sequence in the class lists. The first and second child of each pair was allocated control and fluoride respectively when, in a table of random digits, an even digit was present. In the case of an odd random digit, the first child was allocated fluoride, and the second one control. A few siblings were found ... were taken into the same pair to guarantee that they did not receive the same treatment at school.”
Allocation concealment (selection bias)	Unclear risk	No information provided.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: “The first and second child of each pair was allocated control and fluoride respectively.” “Control group received exactly the same, just without fluoride.” Comment: Use of placebo described.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: “The first and second child of each pair was allocated control and fluoride respectively.” Comment: Use of placebo described. It is unclear if the examiners were blind to treatment allocations, although it is probable that clinical and radiographic exams were done independently.
Incomplete outcome data (attrition bias) All outcomes	High risk	Overall dropout for length of follow‐up: 30% in 2 years. Dropout by group: NR. Reasons for losses: Exclusions based on use of orthodontic bands and presence in all follow‐up examinations. Comment: Numbers lost unduly high for length of follow‐up; any differential losses not assessable. 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: DFS increment (CA)CL + (DR)XR, reported at 1 and 3 year follow‐ups. 1stmPF‐DFS 1stmMD‐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: DMFS: 2.24 (FD), 2.75 (PL) 1stmDMFS: 0.1 FD, 0.1 PL Comment: Initial caries appears balanced between groups. Age also reported, and balanced.
Free of contamination/co‐intervention?	Unclear risk	No information provided.