This clinical trial will evaluate the effectiveness and cost-effectiveness of a link work intervention for supporting people with severe mental health difficulties to attend a routine dental appointment. There are two main outcomes, namely: i) attendance at a routine dental appointment; and ii) oral health quality of life.

The main predictions are that:

1. The link work intervention plus treatment as usual will lead to greater likelihood of attendance at a routine dental appointment, compared with treatment as usual alone.
2. The link work intervention plus treatment as usual will lead to better oral health quality of life, compared with treatment as usual alone.
3. The link work intervention plus treatment as usual will be cost-effective compared with treatment as usual alone.

Aim: To evaluate the effectiveness and cost-effectiveness of a link work intervention to facilitate dental attendance in people with severe mental illness.

Methods: An effectiveness randomised-controlled trial with integrated cost-effectiveness analysis and process evaluation. 480 participants will be recruited from five NHS Trusts and randomised (ratio 1:1) to either treatment as usual or treatment as usual plus the link work intervention. The link work intervention will follow the manual co-developed and used in the feasibility trial. Blind research assistants will support participants to complete assessments at baseline and after nine-months. The investigators will obtain consent to access participant's dental visiting data via the Business Services Authority. The primary outcomes are i) attendance at a routine dental appointment, and ii) oral health related quality of life. Health economics analysis will assess whether the intervention is cost-effective. A qualitative process evaluation will help to understand how it works and might be implemented.

Results/conclusions: This research hopes to produce the first evidenced-based intervention for improving the oral health of people with severe mental illness. It could help to overcome inequities in dental access.

Inclusion Criteria:

• Aged ≥18 years.
• Receipt of care from community mental health or early intervention teams at the point of referral.
• No routine dental appointment (e.g. high street dentist, special care dentist service) in the past three years. This would include any dental examination, diagnosis, advice or treatment (e.g. fillings, root canal, extractions, crowns, dentures, bridges) resulting from a routine (non-emergency) appointment at a dental service. Emergency dental care (e.g. emergency attendance at an Accident & Emergency Appointment or a dental hospital) is not included within this definition, although any follow-up routine and planned appointments with a dentist would exclude the person from taking part.
• Able to provide informed consent as determined by trained researchers in consultation with the clinical team.

Exclusion Criteria:

• Current inpatient status on psychiatric ward. This does not include people in rehabilitation homes or supported accommodation in the community.
• Immediate risk to self or others operationalised as the presence of active intent or planning to harm oneself or others in the near future (e.g. next month). Where individuals are excluded on this basis, with the person's consent, the researcher will aim to re-contact them and/or the referrer in approximately one-months' time to determine if risk has subsided to a point where they are now eligible.
• Enrolled in another dental randomised controlled trial.

Following publication of the trial results, the investigators will make suitable arrangements for anonymised data to be available from the research team, in line with NIHR data sharing guidance. This will be outlined in the Data Access Management Plan (DAMP) developed in the early phases of the project.

Exact plans and timescales will be developed during the early phases of the project and outlined within a Data Access Management Plan (DAMP). The IPD will only be available from the point of the results being published and after 31/07/2029.

Exact specifications around who can apply for access to anonymized data and how will be outlined in the Data Access Management Plan (DAMP). Key considerations will include the confidentiality and privacy of participants; respect to the terms of consent by individuals who are involved in research; consistency with relevant legal, ethical and regulatory frameworks; and guarding against unreasonable costs.

Research assistants undertaking clinical assessments will be blind to the treatment allocation. The investigators will monitor and record all breaking of the blind on a structured form. The co-investigator team, TSC and DMC will review blind breaks to establish and implement learning and reduce further blind breaks. Where possible, when one researcher becomes unblinded, a second unblinded researcher will complete the assessment. Deliberate unblinding of the researchers during the trial is unlikely, but will be considered by the senior management team and could occur in cases of risk or safeguarding. Statisticians will be masked to randomisation outcome until finalisation of the statistical analysis plan to avoid bias.