Clear aligner orthodontic therapy of rotated mandibular round-shaped teeth: A finite element study

Abstract

Objective: To evaluate, using the finite element method, the orthodontic rotational movement of a lower second premolar obtained with clear aligners, analyzing different staging and attachment configurations. Materials and Methods: A CAD model including a complete lower dental arch (with element 4.5 mesially rotated 308) and the corresponding periodontal ligaments, attachments, and aligner was designed and imported to finite element software. Starting from the CAD model, six projects were created to simulate the following therapeutic combinations for correcting element 4.5 position: (1) without attachments, (2) single attachment placed on the buccal surface of element 4.5, (3) three attachments placed on the buccal surfaces of teeth 4.4 to 4.6. For each project, both 1.28 and 38 of aligner activation were considered. Results: All the analyzed configurations revealed a clockwise rotation movement of element 4.5 on the horizontal plane. Models with attachments showed a greater tooth displacement pattern than models without attachments. Simulations with attachments and 38 of aligner activation exhibited the best performance concerning tooth movement but registered high stresses in the periodontal ligaments, far from the ideal stress levels able to produce tooth rotational movement. Conclusions: The model with a single attachment and 1.28 of aligner activation was the most efficient, followed by the three attachment model with the same degree of activation. Aligner activation should not exceed 1.28 to achieve better control of movement and reasonable stress in periodontal structures. (Angle Orthod. 2020;90:247-254.)

Clear aligners for maxillary anterior en masse retraction: a 3D finite element study

“…Several experimental approaches have been carried out on the biomechanics of possible tooth movement with clear aligners. Compared to displacement measurements and strain gauge measurements, 3D FE analysis has the advantage of taking periodontal tissues into consideration and can calculate the stress, strain and displacement of any part of the tooth and aligner 11,[22][23][24][25][26][27] . However, most FE studies on clear aligners were limited to a single tooth or a segment of teeth 11,[22][23][24]26 .…”

“…Auxiliaries such as attachments were mandatory in clear aligner therapy to achieve desired results 25,26,32 . While some reports pointed out that customized attachments could facilitate complex movements, others failed to find significant differences in the shape and position of attachments on tooth movement 16,20,22,26 .…”

Quantitative evaluation of implemented interproximal enamel reduction during aligner therapy:

“…With the increased popularity of aligner therapy and its improving effectiveness in contemporary orthodontics, 1,2 interest in enamel interproximal reduction (IPR) has grown, as it is being considered as one of the major space-gaining orthodontic procedures. The cortical bone represents the limit for orthodontic tooth movement, which should be considered especially during treatment of crowding with proclination and expansion.…”

Three-Dimensional Finite Element Analysis on En-Mass Retraction of Maxillary Anterior Teeth With the Clear Aligner Technique

“…Fortunately, in the last few years, with the leaping forward of CA technology and in-depth research on biomechanical mechanisms, the performance of the diaphragm material has been improved, which has enabled the CA to be gradually used in the orthodontic treatment of complex extraction cases [16,17]. In clinical, a series of small tooth movements are completed by wearing a range of aligners mentioned above, and nally, the teeth are positioned [10,18]. Therefore, to reveal the system biomechanical principles, the biomechanical principles of CA without assistive devices to close the extraction space of the premolars should be initially studied, and the clinical and later series of studies should be underpinned theoretically.…”

“…Therefore, to reveal the system biomechanical principles, the biomechanical principles of CA without assistive devices to close the extraction space of the premolars should be initially studied, and the clinical and later series of studies should be underpinned theoretically. Considering the complexity of orthodontic biomechanics and the principles of medical ethics, biomechanics in related elds cannot be effectively studied in vivo [10]. Therefore, the use of the nite element method in vitro simulation research makes up for a defect of the current research,and provides a better research direction for orthodontic biomechanics research.…”