Patient Adherence to Splint Therapy and Counselling Programmes in Temporomandibular Disorders: Development and Validation of a New Questionnaire

Background Adherence to conservative treatments is essential for optimal outcomes in temporomandibular disorder (TMD) patients, yet validated tools for measuring adherence are lacking. Purpose This study aimed to develop and validate a bilingual (Arabic–English) questionnaire to comprehensively assess adherence among TMD patients. Study Design, Setting, Sample A cross‐sectional, observational, five‐phase design was conducted at the Oral and Maxillofacial Surgery Department, Faculty of Dentistry, Mansoura University (Egypt). The study included a pilot sample of 60 TMD patients and a psychometric evaluation sample of 300 patients. Exposure The exposure was adherence behaviour, measured by a newly developed 50‐item, 11‐domain adherence questionnaire. Main Outcome Variable(s) The primary outcomes were psychometric properties of the questionnaire, including content validity, internal consistency, test–retest reliability and construct validity. Covariates Patient language version (Arabic or English) was considered to examine potential influences on questionnaire performance. Analyses Content validity was assessed using Item‐Content Validity Index (I‐CVI) and Content Validity Ratio (CVR). Reliability was evaluated with Cronbach's α and intra‐class correlation coefficient (ICC). Construct validity was examined with exploratory factor analysis (EFA). Results The final 50‐item, 11‐domain questionnaire demonstrated strong content validity. Internal consistency was acceptable for both Arabic (Cronbach's α = 0.70) and English ( α = 0.68) versions. Test–retest reliability was good (ICC = 0.762–0.898; p < 0.001). EFA confirmed 11 domains, accounting for 61.5% of variance in Arabic and 64.73% in English. Conclusions and Relevance The Badawy and Haggag Adherence Questionnaire for TMD demonstrated strong validity and reliability across Arabic and English versions. It provides a robust clinical and research tool for assessing adherence to conservative TMD management, enabling clinicians to identify non‐adherence and design tailored interventions to improve outcomes. Trial Registration ClinicalTrials.gov ID NCT07045441. The trial was first posted on 22 June 2025, and the most recent update was posted on 30 June 2025. Retrospectively registered