Promoting regular parental supervised toothbrushing: An additive intervention design adopting the Health Action Process Approach.

The study aimed to test the efficacy of the core elements of the Health Action Process Approach (HAPA) in an intervention among parents to promote regular supervised toothbrushing of preschool-aged children. The pre-registered study (https://osf.io/fyzh3/) tested the effects of an intervention employing information provision, behavioural instruction, implementation intention and mental imagery techniques, adopting a randomised controlled design in a sample of Australian parents of preschoolers (N = 254). The intervention used an additive design with four conditions-education, self-efficacy, planning and action control-progressively layered to show the cumulative impact of incorporating self-efficacy, planning and action control strategies with a foundational education component. The intervention was delivered online, and participants completed self-report measures of parental supervised toothbrushing and HAPA-based social cognition constructs pre-intervention and 4 weeks post-intervention. Although no significant intervention effects on behaviour were observed, mixed-model analyses of variance (ANOVAs) revealed an increase in intention and task self-efficacy within the action control condition and an increase in action planning in both the action control and planning conditions from pre-intervention to follow-up. Despite no anticipated changes in behaviour, these findings endorse the use of theory- and evidence-based behaviour change strategies to inspire change in HAPA-based determinants of parental supervised toothbrushing: intention, action planning and task self-efficacy.