Background
Poor oral health is common among older adults residing in care homes impacting their diet, quality of life, self-esteem, general health and well-being. The care home setting is complex and many factors may affect the successful implementation of oral care interventions. Exploring these factors and their embedded context is key to understanding how and why interventions may or may not be successfully implemented within their intended setting.

Objectives
This methodology paper describes the approach to a theoretically informed process evaluation alongside a pragmatic randomised controlled trial, so as to understand contextual factors, how the intervention was implemented and important elements that may influence the pathways to impact.

Materials and methods
SENIOR is a pragmatic randomised controlled trial designed to improve the oral health of care home residents in the United Kingdom. The trial uses a complex intervention to promote and provide oral care for residents, including education and training for staff.

Results
An embedded, theoretically informed process evaluation, drawing on the PAHRIS framework and utilising a qualitative approach, will help to understand the important contextual factors within the care home that influence both the trial processes and the implementation of the intervention.

Conclusion
Utilising an implementation framework as the basis for a theoretically informed process evaluation provides an approach that specifically focuses on the contextual factors that may influence and shape the pathways to impact a given complex intervention a priori, while also providing an understanding of how and why an intervention may be effective. This contrasts with the more common post hoc approach that only focuses on implementation after the empirical results have emerged.