Table 6 Summary of intervention refinements for a definitive RCT with rationale based on feasibility study (phase 2)

Screening and recruitment strategies

1. The following exclusion criteria question was changed to:

Has the participant received natural tooth replacement (removable dentures or fixed prosthodontics) for partial tooth loss within the previous 5 years?

2. The screening questionnaire was modified to incorporate additional patient information including GP details, type of natural tooth replacement, current oral health issues, method of recruitment, and note sections. A protocol giving a step by step guide for the researcher was also included within the questionnaire.

3. Addition of a poster advert to recruitment strategies.

4. Incorporation of offering home visits for study appointments.

1. Tooth replacement criteria were widened to increase the pool of eligible patients in order to meet the proposed RCT sample size.

2. The screening questionnaire was modified to allow for a more robust and systematic screening process and to incorporate added requirements from the RCT. A step by step guide was integrated to ensure adherence to the research protocol and to facilitate a standardised screening process between researchers.

3. Poster adverts were put up around the Centre for Dentistry as a means of expanding recruitment.

4. Conducting study appointments at participant’s homes were offered in order to maximise engagement by overcoming accessibility barriers to the Centre for Dentistry.

Data collection procedures

Additional questionnaires, anthropometric measurements and health outcomes from phase 2 were suggested for an RCT including:

Questionnaires

1. An oral health section using the NDNS ‘Oral Health module’ [33].

2. International Physical Activity Questionnaire (IPAQ) [32].

3. Oral Health-related Quality of Life using the Oral Health Impact Profile (OHIP-14) [34].

4. General Nutrition Knowledge Questionnaire [35].

5. EuroQol Five Dimensions–5 level Questionnaire (EQ-5D-5L) [36].

Anthropometric measurements

1. Waist and hip circumference

2. Body composition measurements

Health outcomes

1. Muscle strength

2. Blood pressure

3. Blood and saliva samples

Phase 2 was primarily to test the feasibility of the intervention itself. However, in order to capture a wider overview of overall health outcomes, data collection measures were incorporated into a definitive RCT.

Intervention delivery

1. Collapsing the 6-week intervention session with the 2-month follow-up assessment.

2. The delivery protocol was amended to incorporate additional study measures and RCT follow up time points.

1. It was apparent that a two month follow-up assessment was not required as study measures could be collected at the 6-week intervention session. A reduction in the number of study visits also reduced the burden of participant involvement in the study.

2. Amendment of the delivery protocol facilitated a better flow to study appointments and ensured adherence to the research protocol and appropriate documentation of participant data.

Study materials

1. Minor changes to the dietary intervention booklet.

2. Further development of a study equipment list, participant information sheet, invitation letter and letter of acceptance.

1. Minor changes to the intervention booklet to amend noticed spelling mistakes/grammatical errors and to incorporate wholegrain serving suggestions [26].

2. Further development of the study equipment list, participant information sheet, invitation letter and letter of acceptance allowed incorporation of RCT requirements.