Torell 1965b.

Methods	Trial design: 2‐armed, double‐blind, placebo‐controlled RCT Location: Sweden Number of centres: not reported. Södertälje, Stockholm, Sweden Recruitment period: study began 1962
Participants	Inclusion criteria: not reported Exclusion criteria: mental disability; recipients of previous fluoride treatment; inhabitants of water supply area containing > 0.5 ppm F Baseline caries: 15 DMFS (from sample randomised) (Gp A: 14.52 DMFS (SE 0.63); Gp B: 15.41 DMFS (SE 0.72)). Baseline characteristics (DMFS, MD‐DMFS) "balanced" Age at baseline (years): mean 11 years (group distribution not reported) Sex: distribution not reported numerically; "equal number of girls and boys" Any other details of important prognostic factors: background exposure to fluoride: none reported. Community water supply naturally fluoridated < 0.3 ppm F Number randomised: 432 (Gp A: 215; Gp B: 217) Number evaluated: 368 at 2 years (available at final examination) (Gp A: 188; Gp B: 180) Attrition: 15% dropout rate after 2 years (study duration = 2 years). Reasons for attrition natural losses mainly; no differential group losses
Interventions	Comparison: FT versus PL Gp A (n = 215): SMFP 1000 ppm F; abrasive system: Ca carbonate; home use/unsupervised, twice a day instructed but daily frequency assumed, post‐brushing water rinse instructed Gp B (n = 217): placebo; abrasive system: Ca carbonate; home use/unsupervised, twice a day instructed but daily frequency assumed, post‐brushing water rinse instructed
Outcomes	Primary: 2‐year DMFS increment ‐ (CA) cl; MD‐DMFS; FS (at 2 years) Secondary: none assessed Assessments irrelevant to this review's scope: n/a Follow‐up duration: 2 years
Notes	Adverse effects: not reported Funding source: Swedish Medical Research Council; County of Stockholm; [Swedish] National Board of Health. Toothpastes provided by Swedish Association of Manufacturers of Fluoride Toothpastes and Procter & Gamble Declarations/conflicts of interest: institutional affiliations reported only Data handling by review authors: study reports 2 age groups separately, see Torell 1965a for younger age group. SDs imputed from SEs in analyses using standard Cochrane methods Other information of note: clinical (VT) caries assessment by 1 examiner, diagnostic threshold = CA; radiographic assessment (BW) by 2 examiners, diagnostic threshold = DR. State of tooth eruption included not reported. Intra‐examiner reproducibility check done for clinical caries in a sample; duplicate examination of x‐rays records done and any discrepancies discussed before final diagnosis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The groups were randomly constituted and randomly assigned to the test different test methods, according to a system worked out with the assistance of statisticians..."
Allocation concealment (selection bias)	Unclear risk	No information provided
Blinding (performance bias and detection bias) All outcomes	Low risk	Quotes: "The control dentifrice had the same composition with the exception of the fluoride" and "On the registration charts the different groups were referred to by their code numbers. The examiners did not have access to the code during the course of the investigation" and "The study was a blind test as the examination charts did not refer to the treatment or to the code number of the groups"                      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: 15% in 2 years. Dropout by group: 27/215 FT, 37/217 PL. Reasons for losses: changing school, moving away, appearance of new caries, unpleasant taste (not reported by group) Comment: numbers lost were not unduly high for the length of follow‐up with no differential losses between groups (12.6% FT, 17.1% PL). It is unclear if reasons for missing outcome data are acceptable and balanced. Caries data used in analysis pertain to participants present at final examinations
Selective reporting (reporting bias)	Low risk	Outcomes reported: DMFS increment ‐ (CA) cl, reported at 2 years follow‐up MD‐DMFS FS 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 (xr): 3.76 FT, 4.13 PL DMFS (cl): 14.52 FT, 15.41 PL mean age: 11 years (both groups) Comment: initial caries appears balanced between groups
Free of contamination/co‐intervention?	Unclear risk	Comment: no information provided