Orthodontic treatment is expected to improve both objective occlusal relationships and patient-centered perceptions of oral function, appearance, and psychosocial well-being. This study applied longitudinal statistical modeling to evaluate how clinical orthodontic outcomes and oral health-related quality of life changed from pre-treatment through active treatment and two retention intervals. The central purpose was to determine whether early improvements in occlusion and aesthetics predicted durable quality-of-life benefits after appliance removal. A prospective cohort of patients receiving comprehensive fixed-appliance therapy was assessed at four time points: pre-treatment, debond, 12-month retention, and 24-month retention. Occlusal outcomes were measured using the Peer Assessment Rating index and the American Board of Orthodontics objective grading system. Patient-reported outcomes were captured using the Oral Health Impact Profile-14 and the Psychosocial Impact of Dental Aesthetics Questionnaire. Linear mixed-effects models were used to estimate average changes over time while accounting for repeated measurements within patients. Latent class growth analysis was applied to identify heterogeneous patterns of psychosocial response across treatment and retention. Models adjusted for baseline malocclusion severity, age, sex, treatment duration, extraction status, and baseline quality-of-life burden. The cohort showed marked improvement in occlusal scores and patient-reported quality of life at debond, with most gains maintained through 24-month retention. Mild post-retention relapse was observed in a subset of patients and was associated with small deterioration in psychosocial domains rather than large changes in functional limitation. Three quality-of-life trajectories were identified: high-improvers, moderate-improvers, and minimal-responders. The study was limited by its single-center design, 24-month retention window, and incomplete follow-up among a minority of participants. Its originality lies in simultaneously modeling objective orthodontic correction and subjective quality-of-life change across both active treatment and retention. The findings support routine integration of patient-reported outcomes into long-term orthodontic success evaluation.
