Development and Validation of a Patient-Reported Outcome Questionnaire for Children Undergoing Removable Orthodontic Treatment

Background/Objectives: Patient-reported outcome measures (PROMs) complement clinical indicators in orthodontics, yet validated instruments for children undergoing removable orthodontic treatment remain limited. This study aimed to develop and validate a questionnaire assessing compliance and physical discomfort, psychosocial impact, and perceived support. Methods: A cross-sectional validation study included 250 children and adolescents (<14 years) treated with removable orthodontic appliances, regardless of treatment duration. The 14-item questionnaire was evaluated for internal consistency (Cronbach’s alpha), reliability (intraclass correlation coefficient, ICC), item discrimination (ANOVA), and construct validity using exploratory factor analysis with Varimax rotation. Sampling adequacy was assessed using the Kaiser–Meyer–Olkin (KMO) measure and Bartlett’s test of sphericity. Results: Internal consistency was satisfactory (Cronbach’s alpha: 0.747–0.823), with corrected item–total correlations above 0.30. ICC values indicated moderate reliability for single measures and good reliability for average measures. The KMO value was 0.713, and Bartlett’s test was significant (p < 0.001). Three factors explained 58.69% of the total variance, representing psychosocial impact, compliance/discomfort, and perceived support. Conclusions: The questionnaire demonstrated satisfactory reliability and construct validity for assessing patient-reported outcomes in children undergoing removable orthodontic treatment. It provides a practical instrument for evaluating compliance and physical discomfort, psychosocial impact, and perceived support in both clinical practice and research.