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Biomechanical reevaluation of orthodontic asymmetric headgear

Chi, Lu and Cheng, Mulin and Hershey, H. Garland and Nguyen, Tung and Ko, Ching-Chang (2012) Biomechanical reevaluation of orthodontic asymmetric headgear. Angle Orthodontist, 82 (4). pp. 682-690. ISSN 0003-3219. doi:10.2319/052911-357.1.

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Objective: To investigate the distribution of distal and lateral forces produced by orthodontic asymmetric headgear (AHG) using mathematical models to assess periodontal ligament (PDL) influence and to attempt to resolve apparent inconsistencies in the literature. Materials and Methods: Mechanical models for AHG were constructed to calculate AHG force magnitudes and direction using the theory of elasticity. The PDL was simulated by elastic springs attached to the inner-bow terminals of the AHG. The total storage energy (Et) of the AHG and the supporting springs was integrated to evaluate the distal and lateral forces produced by minimizing Et (Castigliano’s theorem). All analytical solutions were derived symbolically. Results: The spring-supported headgear model (SSHG) predicted the magnitude and distribution of distal forces consistent with our data and the published data of others. The SSHG model revealed that the lateral forces delivered to the inner-bow terminals were not equal, and the spring constant (stiffness of the PDL) affected the magnitude and direction of the resultant lateral forces. Changing the stiffness of the PDL produced a greater biomechanical effect than did altering the face-bow design. The PDL spring model appeared to help resolve inconsistencies in the literature between laboratory in vitro experiments and clinical in vivo studies. Conclusion: Force magnitude and direction of AHG were predicted precisely using the present model and may be applied to improve the design of AHG to minimize unwanted lateral tooth movement. (Angle Orthod. 2012;82:682–690.)

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Additional Information:© 2012 by The EH Angle Education and Research Foundation, Inc. Received: June 2011; Accepted: October 2011 ;Published Online: December 8, 2011. This study was supported by the American Association of Orthodontists Foundation, National Institutes of Health #K08DE018695, and University of North Carolina Research Council.
Funding AgencyGrant Number
American Association of Orthodontists FoundationUNSPECIFIED
University of North Carolina Research CouncilUNSPECIFIED
Subject Keywords:Orthodontics; Headgear; Biomechanics; Elasticity; Dental
Issue or Number:4
Record Number:CaltechAUTHORS:20120813-110404306
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Official Citation:Lu Chi, Mulin Cheng, H. Garland Hershey, Tung Nguyen, and Ching-Chang Ko (2012) Biomechanical reevaluation of orthodontic asymmetric headgear. The Angle Orthodontist: July 2012, Vol. 82, No. 4, pp. 682-690. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:33125
Deposited By: Aucoeur Ngo
Deposited On:13 Aug 2012 18:22
Last Modified:09 Nov 2021 21:32

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