Process evaluation of a secondary school‐based digital behaviour change intervention to improve toothbrushing: the BRIGHT randomised controlled trial

Objectives The aim was to conduct a process evaluation of a multicomponent behaviour change intervention to reduce dental caries in secondary school children in the UK. The intervention was evaluated in the BRIGHT randomised controlled trial which investigated clinical and cost-effectiveness. The trial involved 4680 participants from 42 schools with a follow-up period of 2.5 years. Schools with an above-average proportion of free school meal (FSM) eligibility, an indicator of low household income, were recruited. The intervention, an oral health classroom-based session (CBS) delivered by school staff and twice-daily text messages aimed to improve toothbrushing frequency with fluoride toothpaste.

Methods Key components of process evaluations were examined: Implementation (fidelity, dose delivered, adaptations and reach), mechanisms of impact (acceptability and dose received) and influential contextual factors. Data collection ran alongside that of the outcome evaluation. Mixed-methods data collection comprised pupil self-reported questionnaires, staff feedback questionnaires, CBS and text message delivery logs and semi-structured interviews/focus groups with school staff and pupils. Quantitative data were summarised descriptively, while framework analysis was applied to the qualitative data.

Results The intervention was generally implemented as intended, albeit with some schools not confirming CBS delivery and a technical problem resulting in text messages being stopped prematurely. Some adaptations to the CBS were made by school staff. In terms of reach, 21.9% (n = 1025) of participants were FSM-eligible. At baseline, 77.6% (n = 3631) of randomised participants reported brushing at least twice daily with no difference over time in the social cognitive determinants of toothbrushing behaviour. The intervention was generally found to be acceptable with varying levels of participant responsiveness reported. The actual dose received was unclear; some schools did not provide a CBS attendance register, and some participants reported blocking or muting the text messages.

Conclusions This evaluation raises the question of whether the intervention dose and quality of delivery were sufficient to support the required behaviour change mechanisms. Moreover, a high proportion of participants brushed twice daily at baseline; this also calls into question the intervention's ability to bring about significant change. The trial findings did not favour the implementation of the two-component intervention (CBS and text messages) within a school setting. However, with oral health as part of the general health school curriculum, the BRIGHT CBS could be adopted within the UK curriculum as it was co-developed with young people and was found acceptable to pupils and teachers.