Designing complex interventions: A description of the development of an intervention to reduce inequalities in planned dental visiting

There are multifaceted reasons for a social gradient in planned dental visiting involving various psycho-social variables that interact with each other and the environment. Interventions in this area are therefore inevitably complex interventions. While guidance recommends undertaking theory and modelling work before experimental work is done, there is a shortage of descriptions of how this is done, especially in the field of oral health.To describe theory, qualitative and public engagement work, and identification of behaviour change techniques (BCTs) to define features of an opportunistic dental visiting intervention for adult users of urgent dental care services.A systematic review and synthesis of theory, qualitative and quantitative work, along with expert input, generated a list of psycho-social determinants linked to planned dental visiting intentions. Modelling involved ethnographic work in urgent dental care settings and work with members of the community from the targeted demographic. This enabled verification, in the context of their idiosyncratic expression for the target population in question, of behavioural determinants (BDs) identified in the theory phase. It also facilitated generating intervention material which was infused with the identity of the end user. BDs identified were then mapped to BCTs using an accepted BCT taxonomy and an intervention prototype developed. The prototype then underwent iterative testing with target users before it was ready for a feasibility trial.Theory and modelling identified five key intervention focuses: affordable resources (time/ cost), the importance of oral health, trust in dentists, embarrassment of having poor oral health and dental anxiety. Short videos were developed to incorporate role modelling which were well received. Prototype testing resulted in shifting from 'if-then' plans to action planning.Complex intervention development involves an iterative rather than sequential process of combining theory, empirical work and user involvement, of which the article provides an example.