Korean J Orthod.  2011 Jun;41(3):191-199. 10.4041/kjod.2011.41.3.191.

Effects of orthodontic mini-implant position in the dragon helix appliance on tooth displacement and stress distribution: a three-dimensional finite element analysis

• Kim MJ
• Park SH
• Kim HS
• Mo SS
• Sung SJ
• Jang GW
• Chun YS

• KMID: 1975431
• DOI: http://doi.org/10.4041/kjod.2011.41.3.191

Abstract

OBJECTIVE
The purpose of this study was to investigate the stress distribution on the orthodontic mini-implant (OMI) surface and periodontal ligament of the maxillary first and second molars as well as the tooth displacement according to the OMI position in the dragon helix appliance during scissors-bite correction.
METHODS
OMIs were placed at two maxillary positions, between the first and the second premolars (group 1) and between the second premolar and the first molar (group 2). The stress distribution area (SDA) was analyzed by three-dimensional finite element analysis.
RESULTS
The maximal SDA of the OMI did not differ between the groups. It was located at the cervical area and palatal root apex of the maxillary first molar in groups 1 and 2, respectively, indicating less tipping in group 2. The minimal SDA was located at the root and furcation area of the maxillary second molar in groups 1 and 2, respectively, indicating greater palatal crown displacement in group 2.
CONCLUSIONS
Placement of the OMI between the maxillary second premolar and the maxillary first molar to serve as an indirect anchor in the dragon helix appliance minimizes anchorage loss while maximizing the effect on scissors-bite correction.

Keyword

Orthodontic mini-implant; FEM

MeSH Terms

Bicuspid
Crowns
Displacement (Psychology)
Finite Element Analysis
Molar
Periodontal Ligament
Tooth

Figure

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  Fig. 1 Clinical application of the dragon helix appliance for tipping and intruding the maxillary second molar.

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  Fig. 2 The stress distribution on the periodontal ligament of the maxillary first and second molars as well as the orthodontic mini-implant (OMI) according to the OMI position. The color change from blue to red indicates increase in force. 4th & 5th OMI and 5th & 6th OMI indicate OMIs implanted between 1st and 2nd premolars, and between 2nd premolar and 1st molars, respectively.

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  Fig. 3 Displacement of the orthodontic mini-implant according to its position (magnification, × 500). White and blue indicate before and after the force application, respectively. 4th & 5th OMI and 5th & 6th OMI indicate OMIs implanted between 1st and 2nd premolars, and between 2nd premolar and 1st molars, respectively.

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  Fig. 4 Graph representing the displacement of the OMI (from the center of the head to the screw end tip, magnification × 1,000). The larger X, Y, and Z values indicate mesial, buccal, and apical movements, respectively. OMI, Orthodontic mini-implant; 4 - 5, between 1st and 2nd premolars; 5 - 6, between 2nd premolar and 1st molar.

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  Fig. 5 Displacement of the maxillary first molar according to mini-implant's position. White and blue indicate before and after the force application, respectively. 4th & 5th OMI and 5th & 6th OMI indicate OMIs implanted between 1st and 2nd premolars, and between 2nd premolar and 1st molars, respectively.

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  Fig. 6 Graph representing the displacement of the maxillary first molar (from the palatal cusp tip to the palatal root apex, magnification × 50). The larger X, Y, and Z values indicate mesial, buccal, and apical movements, respectively. 4 - 5, between 1st and 2nd premolars; 5 - 6, between 2nd premolar and 1st molar.

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  Fig. 7 Displacement of the maxillary second molar according to mini-implant's position. White and blue indicate before and after force application, respectively. 4th & 5th OMI and 5th & 6th OMI indicate OMIs implanted between 1st and 2nd premolars, and between 2nd premolar and 1st molars, respectively.

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  Fig. 8 Graph representing displacement of the maxillary second molar (from the palatal cusp tip to the palatal root apex, magnification × 50). The larger X, Y, and Z values indicate mesial, buccal, and apical movements, respectively. 4 - 5, between 1st and 2nd premolars; 5 - 6, between 2nd premolar and 1st molar.

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