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Published on: October 20, 2023
Maxillary arch expansion in different dentition stages using clear aligners: a three-dimensional finite element
Runzhi Guo1, Yuanyuan Zheng2, Zining Chen1
1Department of Orthodontics, National Center of Stomatology, National Clinical Research Center for Oral Diseases, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health, Peking University School and Hospital of Stomatology, 22 Zhongguancun Avenue South, Haidian District, Beijing 10008, China.
Objectives:
To analyze the maxillary arch expansion efficiency and biomechanical mechanisms of clear aligners (CAs) in different dentition developmental stages.
Methods:
Four 3D finite element models of maxillary arch expansion with CA were established to represent distinct dentition stages: (A) early mixed dentition (1, 2, C, D, E, 6); (B) late mixed dentition (1, 2, C, 4, E, 6); (C) early permanent dentition (1, 2, 3, 4, 5, 6); and (D) permanent dentition (1, 2, 3, 4, 5, 6, 7). A 0.2 mm buccal expansion in one CA was simulated for the maxillary posterior teeth. 3D displacement of maxillary teeth and von Mises stress distribution in roots were analyzed.
Results:
The late mixed dentition showed the greatest mid-arch expansion (0.102 mm) with notable buccal tipping, while the early mixed dentition had the least (0.065 mm). Early permanent dentition demonstrated better torque control, with less buccal tipping of first premolars. Posterior-arch expansion was less pronounced than mid-arch expansion: permanent dentition showed smaller first molar displacement (Group C: 0.016 mm, Group D: 0.027 mm), while mixed dentition exhibited palatal molar displacement (Group A: -0.014 mm, Group B: -0.011 mm). Maxillary incisors displayed labial proclination in mixed dentition but lingual inclination in permanent dentition. The highest von Mises root stress was found in the first primary molar of early mixed dentition (0.134 MPa).
Limitations:
The study only analyzes dental expansion and does not take into consideration the sutural maturation status.
Conclusions:
The efficacy and biomechanics of CA maxillary expansion differ by different dentition stages in adolescent patients. In mixed dentition, expansion mainly occurs at the mid-arch, with palatal molar displacement and labial incisor tipping. Permanent dentition achieves more effective posterior arch expansion with better torque control compares to mixed dentition. The clinical applicability of these findings requires cautious interpretation.
