Sønju Clasen 1995.

Methods	Trial design: 2‐armed, single‐blind (assessors), head‐to‐head, cluster‐randomised (participant‐analysed) RCT Location: Germany Number of centres: 10 kindergartens (5 in each cluster), Salzgitter, Germany Recruitment period: study began August 1991
Participants	Inclusion criteria: not reported Exclusion criteria: fluoride supplement (fluoride tablet) consumption Baseline caries: 2.2 dmfs (Gp A: 2.0 dmfs (SD 5.5); Gp B: 2.4 dmfs (SD 6.6)) (evaluated participants only). Baseline characteristics (proportion caries free, dmft) comparable Age at baseline (years): range 2 to 5 years, mean 4 years (Gp A: median 4.1 years; Gp B: median 4.2 years) (evaluated participants only). Baseline characteristic (age) comparable Sex: 77 F:95 M (Gp A: 39 F:44 M; Gp B: 38 F:51 M) (evaluated participants only). Baseline characteristic (sex) comparable Any other details of important prognostic factors: background exposure to fluoride: none reported Number randomised: 319 participants in 10 clusters (Gp A: 164; Gp B: 155) Number evaluated: 172 at 22 months (available at final examination) (Gp A: 89; Gp B: 83) Attrition: 46% dropout after 22 months (study duration 22 months). Reasons for attrition: change in residence or moving to new kindergarten in the area; no differential group losses
Interventions	Comparison: FT versus FT Gp A (n = 164): NaF 1450 ppm F; abrasive system: silica; school use/supervised daily brushing Gp B (n = 155): NaF 250 ppm F; abrasive system: silica; school use/supervised daily brushing
Outcomes	Primary: 2‐year dmfs increment ‐ cl; dmft increment; ds; dt; fs; ft; proportion remaining caries free (at 2 years) Secondary: none assessed Assessments irrelevant to this review's scope: n/a Follow‐up duration: 22 months
Notes	Adverse effects: not reported Funding source: not reported Declarations/conflicts of interest: institutional affiliations reported only Data handling by review authors: sample size adjusted by design effect (ICC 0.05) to account for cluster randomisation Other information of note: cluster‐randomised trial reported as individual randomised. Clinical (VT) caries assessments by 1 examiner. Clinical data only. Intra‐examiner reliability on 30 children. Scott's pi for dmfs 0.89
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: " .... Salzgitter was divided into five geographical areas from which two kindergartens were randomly assigned"
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient information
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Quotes: "Neither the kindergarten children nor the kindergarten staff were aware of the purpose of the study, nor were they told that a toothpaste containing different amount of fluoride was given to other kindergartens" and "At the time of the examinations the examiner was not aware if the child belonged to the study group or not" Comment: clinical assessors blinded, but unclear whether participants and kindergarten staff blinded. Participants very young children so knowledge of intervention unlikely to influence outcome
Incomplete outcome data (attrition bias) All outcomes	High risk	83/155 available for examination in low fluoride group; 89/164 available in the high fluoride group. Total dropout rate of 46% Quote: "The majority of children who failed to complete the study either went to new kindergartens in the area or to a lesser extent change residence" Comment: high dropout rate, mainly due to change of kindergarten or change of residence. Although reasons for dropouts unlikely to be due to intervention, high rates could influence results
Selective reporting (reporting bias)	Low risk	Comment: routine caries diagnosis. No radiographs taken; clinical examination only. All possible caries indices are reported: ds, fs, dmfs, dt ft, dmft, caries free. Data on different surfaces also presented
Baseline characteristics balanced?	Unclear risk	Comment: baseline data only available for those assessed at 22 months. As a cluster‐randomised trial more information about the individual clusters is required to evaluate this
Free of contamination/co‐intervention?	Low risk	Comment: unlikely as cluster randomised. All children used 250 ppm F toothpaste at home but undertook supervised daily brushing with study toothpastes in kindergarten. Children using fluoride supplements were excluded from the study