Muhler 1957.
| Methods | Trial design: 2‐armed, double‐blind, placebo‐controlled, stratified RCT Location: USA Number of centres: 1. 1953 freshman class at Indiana University Recruitment period: study began 1953 | |
| Participants | Inclusion criteria: not reported Exclusion criteria: not reported Baseline caries: DMFS 27.3 for those completing at 12 months (24‐month data not reported). (Gp A: 26.9 DMFS; Gp B: 27.7 DMFS) Age at baseline (years): range 17 to 36 years Sex: not reported Any other details of important prognostic factors: background exposure to fluoride not reported Number randomised: 425 (group distribution not reported) Number evaluated: 247 at 2 years (available at final examination) (Gp A: 131; Gp B: 116) Attrition: 42% dropout after 2 years (study duration = 2 years). Reasons for dropout not described: change of residence, absenteeism, non‐adherence to study protocol; differential group losses unclear as number randomised to groups at baseline not stated | |
| Interventions | Comparison: FT versus PL Gp A (n = evaluated 131): SnF2 1000 ppm F; abrasive system: Ca pyrophosphate; home use/unsupervised, daily frequency assumed Gp B (n = evaluated 116): placebo; abrasive system: Ca pyrophosphate; home use/unsupervised, daily frequency assumed | |
| Outcomes | Primary: 2‐year DMFS increment ‐ cl + xr; DMFS‐P; DMFS‐O; DMFS‐BL; DMFT (at 6 months, 1 year and 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: partial funding from Procter & Gamble. Other source of funding not reported Declarations/conflicts of interest: 1 author (A Radike) employed by toothpaste manufacturer (Procter & Gamble). Remaining author reports institutional affiliation Data handling by review authors: standard deviations imputed from reported P value Other information of note: clinical (VT) caries assessment by 1 examiner, diagnostic threshold not reported. Radiographic assessment by 1 examiner, diagnostic threshold not reported. Criteria for caries diagnosis reported to have been carefully standardized, diagnostic errors not reported. Study report states that methods used in this study were identical to those used in their previous study (Muhler 1955) | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | Quote: "The subjects were then divided into two groups at random after stratification according to caries experience" Comment: not enough information provided |
| Allocation concealment (selection bias) | Unclear risk | No information provided |
| Blinding (performance bias and detection bias) All outcomes | Unclear risk | Quote: ".... were provided with dentifrices the composition of which were identical except that one contained 4 mg of SnF2" Comment: participants blinded. No information provided for blinding of outcome assessment |
| Incomplete outcome data (attrition bias) All outcomes | High risk | Overall dropout for length of follow‐up: 42% in 2 years. Dropout by group not stated. Reasons for losses not stated Comment: numbers lost were high for the length of follow‐up. Cannot establish whether differential loss between groups as number randomised at baseline not reported. It is unclear if reasons for missing outcome data are acceptable and balanced. Caries data used in analysis pertain to participants present at final examination |
| Selective reporting (reporting bias) | Low risk | Outcomes reported: DMFS increment ‐ cl + xr, reported at 6‐, 12‐ and 24‐month follow‐ups DMFT DMFS DMFS‐P DMFS‐O DMFS‐BL Comment: trial protocol not available. All expected outcomes were reported. No standard deviations provided for caries increment outcomes so cannot be entered into meta‐analysis |
| Baseline characteristics balanced? | Low risk | Prognostic factors reported: age, caries Comment: appears balanced |
| Free of contamination/co‐intervention? | Unclear risk | No information provided |