Long-Term Impact of Orthodontic Treatment on Oral Behaviours, Temporomandibular Disorder-Related Pain, and Anxiety: An 18-Month Prospective Study

Objective: Orthodontic treatment is a common approach for correcting malocclusion but is often associated with discomfort. The aim of this study was to assess the longitudinal changes in oral behaviours, temporomandibular disorder (TMD)-related pain and anxiety among university students undergoing orthodontic treatment compared to untreated controls. Materials and Methods: A prospective cohort study was conducted at the University of Trieste, Italy. Participants were grouped based on the presence or absence of active orthodontic treatment and asked to complete an electronic survey comprising the Oral behaviour checklist-21 (OBC-21), TMD pain screener and generalised anxiety disorder-7 (GAD-7) at baseline (T0), after 6 months (T1), 12 months (T2) and 18 months (T3). Repeated measures ANOVA analysed within-group changes over time, while mixed ANOVA assessed group–time interactions. Results: A total of 114 participants completed all follow-ups, with 57 in each group and comparable sex distribution. In the orthodontic group, no significant changes were observed across the three measures (p > 0.05). The non-orthodontic group showed a slight increase in OBC-21 scores after 12 months (p = 0.034) and a decrease in GAD-7 scores after 18 months (p = 0.048). Mixed ANOVA confirmed the absence of significant changes in the pattern of scores between the orthodontic and non-orthodontic groups over time (p > 0.05). Conclusion: Orthodontic treatment does not significantly influence oral behaviours, TMD-related pain or anxiety over time. Routine screening for these factors in orthodontic patients is not required as a standard practice for all orthodontic patients; instead, individualised assessment should be based on clinical indications.