Proof of concept trial for a new theory-based intervention to promote child and adult behavior change.

Interventions to change children's behavior typically target adults or children, but rarely both. The aims were to: (a) evaluate acceptability and feasibility of an innovative theory-based intervention designed to change both child and adult behavior, and (b) generate effect sizes for a definitive randomized controlled trial. The oral health of sixty children aged 5-9 years with a repaired cleft lip and/or palate was assessed before randomization to one of three conditions: (a) control group, (b) intervention group in which children and adults were asked to form implementation intentions, or (c) intervention plus booster group in which adults were additionally sent a reminder about the implementation intentions they and their children formed. Oral health assessments were repeated at 6-month follow-up alongside exit interviews. The procedures proved popular and participants exposed to the intervention additionally reported believing that forming implementation intentions was effective. Descriptive statistics generally showed oral health improvements across all conditions, although the effects were more marked in the intervention plus booster condition, where plaque improved by 44.53%, gingivitis improved by 20.00% and free sugar consumption improved by 8.92% (vs. 6.43% improvement, 15.00% deterioration and 15.58% improvement in the control group, respectively). Data collection procedures were acceptable and the intervention feasible. The effect sizes suggest that the intervention plus booster condition has sufficient promise to proceed to a fully-powered randomized controlled trial. The intervention has the potential to be adapted to tackle other child health behaviors and to be deployed at scale.