Slack 1971.
| Methods | Trial design: 5‐armed, double‐blind, placebo‐controlled RCT Location: UK Number of centres: 21 secondary schools across Hounslow borough, London Recruitment period: study began 1965 | |
| Participants | Inclusion criteria: not reported Exclusion criteria: not reported Baseline caries: 11.6 DMFS (Gp A: 12.20 DMFS; Gp B: 10.87 DMFS; Gp C: 11.59 DMFS; Gp D: 11.81 DMFS) (evaluated participants only). Baseline characteristic (DMFS) "balanced" Age at baseline (years): range 11 to 12 years (Gp A: 12 years 1 month; Gp B: 12 years 1 month; Gp C: 12 years 1 month; Gp D: 12 years 0 month). Baseline characteristic (age) "balanced" Sex: not reported overall (Gp A: 47.1% F:52.9% M; Gp B: 47.0% F:53.0% M; Gp C: 47.4% F:52.6% M; Gp D: 47.4% F:52.6% M). Baseline characteristic (sex) "balanced" Any other details of important prognostic factors: background exposure to fluoride: none reported. Baseline characteristic (previous F toothpaste use) "balanced" Number randomised: 2063 (groups relevant to review: 1665; Gp A: 423; Gp B: 412; Gp C: 422; Gp D: 408) Number evaluated: 1415 at 3 years (available at final examination) (groups relevant to review: 1110; Gp A: 260; Gp B: 282; Gp C: 279; Gp D: 289) Attrition: 33% dropout rate after 3 years (study duration = 3 years). Main reasons for dropout: moved away, left school, away on examination day, disliked toothpaste taste, brown staining of teeth; no differential group losses | |
| Interventions |
Comparison: FT (3 groups) versus 'PL'
Gp A (n = 423): SnF2 1000 ppm F; abrasive system: IMP; home use/unsupervised, daily frequency assumed
Gp B (n = 412): SnF2 1000 ppm F; abrasive system: dicalcium pyrophosphate; home use/unsupervised, daily frequency assumed Gp C (n = 422): APF 1000 ppm F; abrasive system: IMP; home use/unsupervised, daily frequency assumed Gp D (n = 408): placebo; abrasive system: not reported; home use/unsupervised, daily frequency assumed |
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| Outcomes | Primary: 3‐year crude DMFS increment ‐ (CA) cl + (ER) xr (at 3 years) Secondary: none assessed Assessments irrelevant to this review's scope: n/a Follow‐up duration: 3 years | |
| Notes | Adverse effects: not reported Funding source: Dr W Elvers and Bristol‐Myers Company, New York Declarations/conflicts of interest: institutional affiliations only Data handling by review authors: 5th study arm ineligible for inclusion in review due to no intervention ("unsupervised"). Gps A + B + C versus D in analyses Other information of note: clinical (VT) caries assessment by 1 examiner, diagnostic threshold = CA; state of tooth eruption included not reported. Radiographic assessment (2 postBW) by 1 examiner, diagnostic threshold = ER. Consistency of clinical diagnosis revealed by 10% sample checks at each examination | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | Quote: "The children were randomly allocated to groups, apart from brothers, sisters and others living in the same household who were allocated to the same group" Comment: not enough information provided |
| Allocation concealment (selection bias) | Unclear risk | No information provided |
| Blinding (performance bias and detection bias) All outcomes | Low risk | Quotes: "Dentifrices were made up in large white tubes marked only with a double letter codes... 3 fluoride and 1 non‐fluoride" and "At the time of examination, the examiner had no knowledge of the group to which any child belonged" 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: 33% in 3 years. Dropout by group: 163/423 FT 1, 153/422 FT 2, 130/412 FT 3, 119/408 PL. Reasons for losses: staining of teeth: 3 FT, 4 PL; unpleasant taste (mainly fluoride groups); moved away, changed school, away on examination day Comment: numbers lost were not unduly high given length of follow‐up with differential losses between groups (FT 1 39%, FT 2 34%, FT 3 32%, PL 29%). It is unclear if reasons for the missing outcome data are acceptable and balanced. Caries data used in the analysis pertain to participants present at final examination. Group losses unlikely to be related to intervention |
| Selective reporting (reporting bias) | Low risk | Outcomes reported: DMFS increment ‐ (CA) cl + (ER) xr, reported at 3 years follow‐up 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: 12.20 FT 1, 11.59 FT 2, 10.87 FT 3, 11.81 PL mean age: 12 years (all groups) gender (M/F percentage): 52.9%/47.8% FT 1, 52.6%/47.4% FT 2, 53%/47% FT 3, 52.6%/47.4% PL F users (percentage): 10.4% FT 1, 11% FT 2, 10.8% FT 3, 10.1% PL Comment: initial caries appears balanced |
| Free of contamination/co‐intervention? | Low risk | Quote: "... children joining the trial were randomly allocated to 5 groups, apart from brothers, sisters and others living in the same household who were allocated to the same group" Comment: there is sufficient indication overall of prevention of contamination/co‐intervention |