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Updated: Jan 10, 2026
Author Spotlight: 3D Movement Assessment of Maxillary Posterior Teeth in Clear Aligner Treatment
Published on: February 23, 2024
Tridimensional Analysis of Maxillary Teeth Movements in Premolar-Extraction Cases Treated With Clear Aligners
Yanqi Wang1, Zhicai Feng2, Ruyue Qiang3
1State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration & National Clinical Research Center for Oral Diseases & Shaanxi Clinical Research Center for Oral Diseases, Department of Orthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, China.
Objectives:
To investigate movements of maxillary teeth in four-premolar extraction cases treated with clear aligners (CAs), as well as their influencing factors.
Materials And Methods:
Forty-seven patients underwent four first or second premolars extractions having been treated with CAs. CBCT images were collected pre- and post-treatment for superimposition and measurement. A paired t-test was employed to compare designed and achieved tooth movements. A linear mixed-effects model was utilized to study the effects of designed tooth movements, age, different premolar extractions, anchorage methods, space closing patterns and attachment types on the tooth movements.
Results:
In the anteroposterior direction, the movements of the incisor crowns were fully achieved, whereas the roots were only poorly achieved. Both the roots and crowns of the canines showed less distal displacement than expected, especially the roots. The crowns of the posterior teeth exhibited greater forward movement than expected compared with their roots. In the lateral displacement (LD), the incisors failed to move distally, with the U2 root showing the greatest discrepancy (P < .001). In the occlusal-gingival direction, the incisor crowns demonstrated increased extrusion, particularly U1. Adolescents exhibited greater discrepancies in U1 crown movements compared with adults (P < .001). Although the magnitude of U6 root discrepancies in LD was similar between adolescents and adults, the direction of movement differed significantly (P < .001). The factors that significantly influenced treatment outcomes included age, staging strategy, attachment design, and anchorage methods.
Conclusions:
In premolar-extraction with CAs, the root of the incisors and entire canines required more retraction in design, and the crown needed more intrusion. Miniscrews can cause uncontrolled tilting movement of U1. Different space closing patterns and attachment types affected the anterior teeth and the anchorage of posterior teeth. These findings provide references for optimizing a treatment plan design using clear aligner treatment.
