Zacherl 1970.
| Methods | Trial design: 2‐armed, double‐blind, placebo‐controlled, stratified RCT Location: USA Number of centres: not reported. Edmonton, Alberta, Canada Recruitment period: study began in/before 1963 | |
| Participants | Inclusion criteria: not reported Exclusion criteria: mental disability Baseline caries: 4.71 DMFS (Gp A: 4.88 (SE 0.24); Gp B: 4.53 (SE 0.23)). Baseline characteristics (DMFS, DMFT, oral hygiene) "balanced" Age at baseline (years): range 6 to 9 years (dental age Gp A: 6.99 (SE 0.17); Gp B: 6.78 (SE 0.17)). Baseline characteristic (dental age) "balanced" Sex: 417 F:485 M (Gp A: 204 F:257 M; Gp B: 213 F:228 M). Baseline characteristic (sex) "balanced" Any other details of important prognostic factors: background exposure to fluoride: none reported. Community water supply naturally fluoridated < 0.1 ppm F Number randomised: 902 (Gp A: 461; Gp B: 441) Number evaluated: 512 at 2.5 years (available at final examination) (Gp A: 251; Gp B: 261) Attrition: 43% dropout after 2.5 years (study duration = 2.5 years). Reasons for attrition not reported; no differential group losses | |
| Interventions | Comparison: FT versus PL Gp A (n = 461): SnF2 1000 ppm F; abrasive system: Ca pyrophosphate; home use/unsupervised, daily frequency assumed Gp B (n = 441): placebo; abrasive system: Ca pyrophosphate; home use/unsupervised, daily frequency assumed | |
| Outcomes | Primary: 2.5‐year DMFS increment ‐ cl + xr; DMFT (at 10 months, 1.5 years, 2.5 years) Secondary: none assessed Assessments irrelevant to this review's scope: n/a Follow‐up duration: 2.5 years (30 months) | |
| Notes | Adverse effects: not reported Funding source: not reported Declarations/conflicts of interest: institutional affiliations reported only Data handling by review authors: study reports 2 age groups separately, see Zacherl 1970a for older age group Other information of note: clinical (VT) caries assessment by 1 examiner, diagnostic threshold not reported. Radiographic assessment (5 to 10 BW) by 1 examiner, diagnostic threshold not reported. State of tooth eruption included not reported. Diagnostic errors not reported | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Quotes: "Only grades 1 and 2, and grade 7 were selected. Each of these 2 age groups were divided into 2 similar subgroups according to age, sex and caries history... Adjacent subjects within arrays were assigned by coin toss to one of two groups simply indicated D or H" |
| Allocation concealment (selection bias) | Unclear risk | Insufficient information |
| Blinding (performance bias and detection bias) All outcomes | Low risk | Quotes: "The investigator did not know which was the control and which was the experimental group" and "The study was double blind" and "The control dentifrice lacked the tin compounds but was otherwise identical" 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: 43% in 2.5 years. Dropout by group: 210/461 FT, 180/441 PL. Reasons for losses: not reported Comment: numbers lost were somewhat high for the length of follow‐up. No differential losses between groups. 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 10 months, 1.5 and 2.5 years follow‐ups
DMFT 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: 5.06 FT, 4.69 PL DMFT: 2.69 FT, 2.51 PL dental age: 6.99 FT, 6.78 PL gender: 257 M, 204 F FT; 228 M, 213 F PL oral hygiene: 1.58 FT, 1.63 PL Comment: initial caries appears balanced |
| Free of contamination/co‐intervention? | Low risk | Quote: "To minimize the possible effect of non‐study dentifrice, enough dentifrice was provided monthly to each individual to supply the household for the test period" Comment: there is sufficient indication overall of prevention of contamination/co‐intervention |