Background: The developmental absence of 1-2 upper front teeth is a common condition, affecting 1 in 50 people worldwide, and affects smile aesthetics and quality-of-life. Treatment is often undertaken in teenagers, but the outcomes have lifelong consequences. Treatment options involve either creating space for a false tooth, or closing space and disguising the adjacent tooth as the missing tooth; both options have their own advantages, disadvantages and long-term considerations, and treatment often requires input from multiple dental specialties. Advances in orthodontic techniques mean more patients can be treated with either approach, therefore, the ideal treatment plan becomes more subjective and based upon the patient's preferences.

Aim: To develop a Patient Decision Aid (PDA), a decision-making support tool to help young people (and parents/guardians) with developmentally missing upper front teeth choose the best treatment option for them.

Approach: First, the investigators will gather information from stakeholders involved in the decision-making process to understand their needs. Interviews will be conducted with young people with developmentally missing upper front teeth and their parents/guardians about their experiences, expectations, and preferences regarding treatment decision-making. Information will also be sought from clinicians involved in this process about their experiences of the decision-making process, via focus groups. These will be carried out across two NHS hospitals with special clinics for missing teeth. Then, the information obtained from both patient and clinician stakeholder groups will help the investigators to develop a PDA, following international guidelines. PDA development will occur alongside ongoing input and feedback from a Development Panel (which will include patients and clinician representatives) to optimise content, acceptability, and accessibility. The final approved PDA will then be trialled in a later pilot study.

Patient Participant Inclusion Criteria:

• Young people with Maxillary Lateral Incisor Agenesis (MLIA) affecting one or both maxillary lateral incisors
• Young people aged 11-18 years old (attending with an adult with parental responsibility if <16 years old)
• In active orthodontic (space-closure or space-opening) or restorative treatment for MLIA, or completed active dental treatment less than one year ago
• Attended a multidisciplinary Hypodontia Clinic for treatment planning where both space-closure and space-opening options were offered

Patient Participant Exclusion Criteria:

• Craniofacial anomalies including cleft lip and/or palate
• Unable to communicate in English where no professional translation service is available

Clinician Participant Inclusion Criteria:

• Specialists or consultants in orthodontics, restorative dentistry, paediatric dentistry, and oral surgery who provide care as part of the Hypodontia pathway and work within the multidisciplinary hypodontia clinics

Clinician Participant Exclusion Criteria:

• Any clinician not providing care as part of the Hypodontia pathway and working within the multidisciplinary hypodontia clinics

Patient Participants: patients attending the dental department for routine appointments Clinician Participants: clinicians working within the dental department