Using realist methods for intervention development to fill a methodological gap: A case study showing the development of an oral hygiene intervention for people with intellectual developmental disabilities.

It is demonstrated how realist methods could be integrated with substantive theory when developing an intervention. RTs enhanced the contextualization of the intervention that was developed but were insufficient in their own right to guide the development process from conception to intervention. This was overcome by augmenting with substantive theory, in this case, using the BCW and BCT behaviour change systems, to select and specify the behaviours that needed to change. In essence, the BCTs guided which techniques to select, while the RTs guided how to develop and intervene. Robust intervention development in the field of oral health promotion is also presented in this study.