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Stress Relaxation In Orthodontic Aligner Plastics; An In Vitro Comparison Study, Kristopher J. Keller
Stress Relaxation In Orthodontic Aligner Plastics; An In Vitro Comparison Study, Kristopher J. Keller
Theses & Dissertations
The purpose of this study was to ascertain if repeated stresses from extension cycling would result in accumulated damage in aligner materials and affect force delivery. A secondary goal was to identify potential differences in mechanical behavior present among orthodontic aligner polymers. Four thermoplastic polymers (Essix ACE, Taglus, Zendura, and Zendura FLX) were thermoformed, cut into strips, and extension cycled to 0.4 millimeters in a 37C water bath. Force decay, maximum and minimum force, and elastic modulus were measured during cycling. Additional samples were subjected to controlled tension until failure, allowing the measurement of yield strength, ultimate strength, and elastic …
Orthodontically Induced External Root Resorption In Extraction Versus Non-Extraction Treatment Modalities – A Retrospective Cone-Beam Computed Tomography (Cbct) Study, Jaykishan Patel
Theses & Dissertations
Purpose of this study was to evaluate orthodontically induced external apical root resorption using cone beam computed tomography in patients receiving orthodontic treatment with or without extractions. Records of 188 consecutively treated patients who received orthodontic treatment with or without extractions were evaluated. Pre-and post-treatment root lengths of maxillary incisors, volumes of maxillary central incisors, and apex displacement of either right or left maxillary central incisors were measured using Invivo 5.4 or ITK-SNAP 3.8.0 software. After adjusting for initial length, treatment duration, tooth, sex, race, bracket type, and malocclusion, maxillary incisor reduction of root length in extraction group was 0.37 …