The korean journal of orthodontics (대한치과교정학회지)

The Korean Association Of Orthodontists (대한치과교정학회)
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Palatal en-masse retraction of segmented maxillary anterior teeth: A finite element study

  • Park, Jae Hyun (Postgraduate Orthodontic Program, Arizona School of Dentistry & Oral Health, A.T. Still University) ;
  • Kook, Yoon-Ah (Department of Orthodontics, The Catholic University of Korea, Seoul St. Mary's Hospital) ;
  • Kojima, Yukio (Department of Mechanical Engineering, Nagoya Institute of Technology) ;
  • Yun, Sunock (Private Practice) ;
  • Chae, Jong-Moon (Postgraduate Orthodontic Program, Arizona School of Dentistry & Oral Health, A.T. Still University)
  • Received : 2018.07.24
  • Accepted : 2019.03.20
  • Published : 2019.05.25
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Abstract

Objective: The aim of this finite element study was to clarify the mechanics of tooth movement in palatal en-masse retraction of segmented maxillary anterior teeth by using anchor screws and lever arms. Methods: A three-dimensional finite element method was used to simulate overall orthodontic tooth movements. The line of action of the force was varied by changing both the lever arm height and anchor screw position. Results: When the line of action of the force passed through the center of resistance (CR), the anterior teeth showed translation. However, when the line of action was not perpendicular to the long axis of the anterior teeth, the anterior teeth moved bodily with an unexpected intrusion even though the force was transmitted horizontally. To move the anterior teeth bodily without intrusion and extrusion, a downward force passing through the CR was necessary. When the line of action of the force passed apical to the CR, the anterior teeth tipped counterclockwise during retraction, and when the line of action of the force passed coronal to the CR, the anterior teeth tipped clockwise during retraction. Conclusions: The movement pattern of the anterior teeth changed depending on the combination of lever arm height and anchor screw position. However, this pattern may be unpredictable in clinical settings because the movement direction is not always equal to the force direction.

Keywords

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