Bayirli, BurcuQuinn, Neal MacKendrick2026-04-202026-04-202026-04-202026Quinn_washington_0250O_29302.pdfhttps://hdl.handle.net/1773/55478Thesis (Master's)--University of Washington, 2026Introduction: Clear aligner therapy is rapidly gaining market share and offers aesthetic and hygienic benefits; however, their efficacy in Class II correction with elastics remains under-researched compared to traditional fixed appliances. Specific Aims: This study compares anteroposterior and vertical dentoalveolar, facial, and skeletal changes between clear aligners and fixed appliances. Differences in treatment efficiency and outcome variations between growing versus non-growing patients were evaluated based on technique. Research Design and Methods: This is a retrospective cohort study involving 132 subjects (64 clear aligner, 68 fixed appliance) categorized into growing and non-growing cohorts based on age. Data collection included lateral cephalometric tracings, 3D digital model analysis, and additional treatment factors such as IPR. Linear regression was used to compare post-treatment variance by adjusting for pre-treatment values. Effect of appliance type on each parameter is represented by the coefficient ß. Results: The analysis revealed no significant difference in treatment time between aligners and fixed appliances (~23–25 months). However, fixed appliances showed significantly more buccal crown torque added to incisors, 9.47º (7.10, 11.8) in adolescents and 8.68° (2.02, 15.3) in adults compared to aligners. Clear aligners demonstrated less vertical change, showing significantly less overbite reduction. Conclusions: Each appliance type offers distinct clinical advantages: clear aligners provide better control of lower incisor torque and vertical dimensions, while fixed appliances may be more effective for deep overbite correction. Skeletal and facial changes were largely similar across both modalities, suggesting outcomes are primarily driven by initial dental and biological factors rather than the appliance type.application/pdfen-USCC BY-NDClass IIElasticsInvisalignLateral CephalometricDentistryDentistryThesis