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Background: There is a growing public health need to identify key strategies that will improve the health of our older adult population. An older person’s diet is a major determinant for successful ageing which is influenced by a wide range of age-related factors. With regards to oral health related factors, research shows that replacing missing teeth alone is not enough to engender dietary behaviour change among older people, highlighting the need for dietary intervention. One approach proven to change food behaviours in the long-term and is novel to this population is that of habit-formation. Aim: The aim of this research is to develop and test a habit-based tailored dietary intervention, in conjunction with oral rehabilitation, and to examine its impact on positive dietary habit-formation amongst partially dentate older adults. Method: This PhD involved (a) a systematic review to identify existing intervention studies where oral rehabilitation was coupled with a purposeful dietary intervention amongst adults (n=9); (b) the development of a habits-based dietary intervention (DENHAB) using desk-based research and a qualitative study (n=21); (c) a feasibility study (n=9) of the DENHAB intervention (face-to-face) amongst older people delivered at fortnightly intervals (6 week follow-up); (d) a randomised control trial (n=57) to evaluate the DENHAB intervention (face-to-face) in combination with oral rehabilitation amongst older people (8 month follow-up); (e) qualitative Patient Public Involvement (PPI) work (n=5) among health professionals to advise on implementation of the DENHAB intervention into clinical care. Results: Findings of the systematic review (Chapter 2) identified improvements in at least one aspect of participants' oral health alongside at least one positive diet/nutrition outcome post-intervention for all studies. Fruit and vegetable results were pooled for three studies using meta-analysis techniques resulting in a standardized mean difference of 0.29 [CI -0.54, 1.12], p = 0.49, but with marked heterogeneity. Few interventions were theory-based and intervention components were poorly described. Overall, the systematic review indicated support for dietary intervention coupled with oral rehabilitation on diet. Meta-analysis was only possible with three studies highlighting limitations and the need for large-scale, appropriately described trial methodologies. This work identified the need for further studies to develop and test dietary interventions combined with oral rehabilitation which lay out a basis for the remaining chapters of this PhD. The DENHAB intervention was designed and developed (Chapter 3) in accordance with the Medical Research Council framework for developing complex interventions (Craig et al., 2013). It was informed by an initial habit-based dietary intervention for parents and adapted to an older adult population using desk-based research (McGowan et al., 2013). Qualitative research (n=21) was then conducted with the target audience to further develop the DENHAB intervention. This evaluation demonstrated that the DENHAB resources were overall well received by participants but informed on changes required before the next phase of the study which were mainly based around formatting, clarity and updates to the habit examples. Following these iterative changes, a feasibility study (n=9) (Chapter 4) was conducted which demonstrated that the intervention was both acceptable and feasible. It also identified the need for further refinement to screening and recruitment strategies, study measures, intervention delivery and study materials. A randomised control trial (Chapter 5) on 57 participants (n=8 dropouts) was then conducted which demonstrated significant differences in the primary outcome measure of habit-forming automaticity for healthy food choices. Whilst a mixture of statistical significance was observed across secondary outcomes, the study illustrated the need for larger trial research in order to investigate key research gaps identified during the course of the study. Qualitative work on health professionals (n=5) advising on implementation of the DENHAB intervention identified the need for future exploratory work to investigate its feasibility particularly regarding best primary care environment and personnel for delivery. Conclusion: The research presented in this thesis has provided a key contribution for the evidence base of a dietary intervention grounded in habit theory, eating behaviour maintenance for older people and the use of a dental setting to provide dietary advice.