Slack 1964.
| Methods | Trial design: 2‐armed, double‐blind, placebo‐controlled, stratified RCT Location: UK Number of centres: 4 secondary schools, Kent, UK Recruitment period: study began 1962 | |
| Participants | Inclusion criteria: not reported Exclusion criteria: not reported Baseline caries: not reported. Baseline characteristics "balanced" Age at baseline (years): range 11 to 13 years (group distribution not reported). Baseline characteristics "balanced" Sex: 459 F:600 M (Gp A: 231 F:303 M; Gp B: 228 F:297 M). Baseline characteristics "balanced" Any other details of important prognostic factors: background exposure to fluoride: none reported. Community water supplies 0.07 ppm F Number randomised: 1059 (Gp A: 534; Gp B: 525) Number evaluated: 719 at 2 years (present for all examinations) (Gp A: 365; Gp B: 354) Attrition: 32% dropout rate after 2 years (study duration = 2 years). Reasons for attrition: natural losses and other reasons; exclusions based on presence in all follow‐up examinations; no differential group losses | |
| Interventions | Comparison: FT versus PL Gp A (n = 534): SnF2 1000 ppm F; abrasive system: IMP; home use/unsupervised, 3 times/day instructed but daily frequency assumed Gp B (n = 525): placebo; abrasive system: dicalcium phosphate (dihydrate); home use/unsupervised, 3 times/day instructed but daily frequency assumed | |
| Outcomes | Primary: proportion of carious teeth/surfaces (by tooth type); proportion of caries‐free teeth/surfaces (by tooth type) developing caries annually (at 1, 2 years) (caries increment data not reported nor obtainable) Secondary: proportion of children with tooth staining (at 1, 2 years) Assessments irrelevant to this review's scope: gum condition, dental cleanliness Follow‐up duration: 2 years | |
| Notes | Adverse effects: stains "In all, 178 black/brown [stains at 1 year examinations] were recorded and it was found subsequently that these fell into both the study and control groups. A similar result was obtained in the 1964 examinations [2 years]. On both occasions, however, there were significantly more black/brown stains in the study groups [Gp A]" Funding source: funded by Unilever Declarations/conflicts of interest: institutional affiliations only Data handling by review authors: n/a Other information of note: clinical (VT) caries assessment by 1 examiner, diagnostic threshold = CA; 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) | Unclear risk | Quote: "The children, whose parents had accepted the invitation, were then allocated at random to the study and control groups" Comment: not enough information provided |
| Allocation concealment (selection bias) | Unclear risk | Comment: no information provided |
| Blinding (performance bias and detection bias) All outcomes | Low risk | Quotes: "The trial was conducted double‐blind; the examiner, scribe and the subjects did not know who was receiving the stannous fluoride dentifrice. Furthermore, the identity of the test group was not disclosed until the analysis of the 2 year results had been completed" and "Control dentifrice issued to control group" 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: 32% in 2 years. Dropout by group: 169/534 FT, 171/525 PL. Reasons for losses: attrition: "three children (boys) who withdrew from the trial. In two cases no reason was given, but in the third case, it was stated that 'the toothpaste was staining the teeth'. This family was receiving the control paste", exclusions based on presence at all examinations Comment: numbers lost were not unduly high given length of follow‐up with no differential losses between groups. It is unclear if reasons for the missing outcome data are acceptable and balanced between groups. Caries data used in the analysis pertain to participants present for all examinations |
| Selective reporting (reporting bias) | Low risk | Outcomes reported:
caries increment (data not obtainable)
proportion of carious teeth/surfaces (by tooth type) reported at 1 and 2 years follow‐ups
proportion of caries‐free teeth/surfaces (by tooth type) which developed caries after each year
proportion of children with tooth staining Comment: trial protocol not available. All pre‐specified outcomes (in Methods) were reported and were reported in the pre‐specified way |
| Baseline characteristics balanced? | Unclear risk | Prognostic factors reported:
percentage DMFT: incisors: 8.6 FT, 8.8 PL; canines: 0.8 FT, 0.7 PL; premolar: 16.2 FT, 17.8 PL percentage DMFS: incisors: 3.3 FT, 3.6 PL; canines: 0.2 FT, 0.2 PL; premolar: 4.8 FT, 4.7 PL Comment: initial caries appears balanced |
| Free of contamination/co‐intervention? | Low risk | Quote: "The aim was to maintain a constant and adequate supply of dentifrice and brushes for the whole family" Comment: there is sufficient indication overall of prevention of contamination/co‐intervention |