A behaviour change intervention (lesson and text messages) to prevent dental caries in secondary school pupils: the BRIGHT RCT, process and economic evaluation

Background: Dental caries impacts on children’s daily lives, particularly among those living in deprived areas. There are successful interventions across the UK for young children based on toothbrushing with fluoride toothpaste. However, evidence is lacking for oral health improvement programmes in secondary-school pupils to reduce dental caries and its sequelae.
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\nObjectives: To determine the clinical and cost-effectiveness of a behaviour change intervention promoting toothbrushing for preventing dental caries in secondary-school pupils.
\nDesign: A multi-centre, school-based, assessor-blinded, two-arm cluster randomised controlled trial with an internal pilot and embedded health economic and process evaluations. 
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\nSetting: Secondary schools in Scotland, England and Wales with above average proportion of pupils eligible for free school meals. Randomisation occurred within schools (year group level), using block randomisation stratified by school.
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\nParticipants: Pupils aged 11-13 years at recruitment, who have their own mobile telephone.
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\nInterventions: Two-component intervention based on behaviour change theory: (i) 50-minute lesson delivered by teachers, and (ii) twice-daily text messages to pupil’s mobile phones about toothbrushing, compared with routine education. 
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\nMain outcome measures: Primary outcome: presence of at least one treated or untreated carious lesion using DICDAS4-6MFT (Decayed, Missing and Filled Teeth) in any permanent tooth, measured at pupil level at 2.5 years. Secondary outcomes included: number of DICDAS4-6MFT; presence and number of DICDAS1-6MFT; plaque; bleeding; twice-daily toothbrushing; health-related quality of life (Child Health Utility 9D); and oral health-related quality of life (CARIES-QC).
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\nResults: 4680 pupils (Intervention, n=2262; Control, n=2418) from 42 schools were randomised. The primary analysis on 2383 pupils (50.9%; Intervention 1153, 51.0%; Control 1230, 50.9%) with valid data at baseline and 2.5 years, found 44.6% in the intervention group and 43.0% in control had obvious decay experience in at least one permanent tooth. There was no evidence of a difference (odds ratio 1.04, 95% confidence interval [CI] 0.85 to 1.26, p=0.72) and no statistically significant differences in secondary outcomes except for twice-daily toothbrushing at 6 months (odds ratio 1.30, 95% CI 1.03 to 1.63, p=0.03) and gingival bleeding score (borderline) at 2.5 years (geometric mean difference 0.92, 95% CI 0.85 to 1.00, p=0.05). 
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\nThe intervention had higher incremental mean costs (£1.02, 95% CI -1.29 to 3.23) and lower incremental mean quality-adjusted life-years (-0.003, 95% CI -0.009 to 0.002). The probability of the intervention being cost-effective was 7% at 2.5 years. However, in two subgroups, pilot trial schools and schools with higher proportions of pupils eligible for free school meals, there was an 84% and 60% chance of cost-effectiveness, respectively, although their incremental costs and quality-adjusted life-years remained small and not statistically significant. The process evaluation revealed that the intervention was generally acceptable although the implementation of text messages proved challenging.
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\nLimitations: The COVID-19 pandemic hampered data collection. High rates of missing economic data mean findings should be interpreted with caution.
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\nConclusions: Engagement with the intervention and evidence of 6-month change in toothbrushing behaviour was positive but did not translate into a reduction of caries.
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\nFuture work: Work with secondary schools pupils to develop an understanding of the determinants of oral health behaviours including toothbrushing and sugar consumption, particularly according to free school meal eligibility. 
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\nTrial registration: ISRCTN12139369.
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\nFunding: This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. X, No. X. See the NIHR Journals Library website for further project information.