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Simulation of miniscrew-root distance available for molar distalization depending on the miniscrew insertion angle and vertical facial type

 Ju-Hyun Yoon  ;  Jung-Yul Cha  ;  Yoon Jeong Choi  ;  Won-Se Park  ;  Sang-Sun Han  ;  Kee-Joon Lee 
 PLOS ONE, Vol.15(9) : e0239759, 2020-09 
Journal Title
Issue Date
Adult ; Bone Screws* ; Computer Simulation* ; Cone-Beam Computed Tomography / methods* ; Female ; Humans ; Male ; Molar / diagnostic imaging* ; Orthodontic Anchorage Procedures / instrumentation ; Orthodontic Anchorage Procedures / methods* ; Tooth Movement Techniques / instrumentation ; Tooth Movement Techniques / methods* ; Tooth Root / diagnostic imaging*
Objective: The purpose of this study was to evaluate the effects of miniscrew insertion angle and vertical facial type on the interradicular miniscrew-root distance available for molar distalization. Materials and methods: Cone-beam computed tomography images of 60 adults with skeletal Class I occlusion exhibiting hyperdivergent (n = 20), normodivergent (n = 20), and hypodivergent (n = 20) facial types were used. Placement of a 6-mm long, 1.5-mm diameter, tapered miniscrew was simulated at a site 4 mm apical to the cementoenamel junction, with insertion angles of 0°, 30°, 45°, and 60° relative to the transverse occlusal plane. The shortest linear distance between the miniscrew and anterior root at four interradicular sites was measured: maxillary second premolar and first molar (Mx 5-6), maxillary first and second molars (Mx 6-7), mandibular second premolar and first molar (Mn 5-6), and mandibular first and second molars (Mn 6-7). Results: Miniscrew-root distance significantly increased as the insertion angle increased from 0° to 60°. In the mandible, the distances significantly differed among vertical facial types, increasing in the following order: hyperdivergent, normodivergent, and hypodivergent. The minimum mean distance was found in the Mx 6-7 (30°; 0.86±0.35 mm), and the maximum mean distance was found in the Mn 5-6 (60°; 2.64±0.56 mm). The rates of miniscrews located buccally outside the root distalization path were up to 70% and 55% when the miniscrews were placed at 60° insertion angles in the Mx 5-6 and Mn 5-6 regions, respectively. Conclusions: Miniscrew-root distance increased significantly with the increased insertion angle, and the amount of increase was affected by the miniscrew placement site and vertical facial type. To ensure adequate distalization of the posterior segment, the miniscrew should be inserted at an angle in the interradicular area between the second premolar and first molar.
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2. College of Dentistry (치과대학) > Dept. of Orthodontics (교정과학교실) > 1. Journal Papers
2. College of Dentistry (치과대학) > Dept. of Oral and Maxillofacial Radiology (영상치의학교실) > 1. Journal Papers
Yonsei Authors
Lee, Kee Joon(이기준) ORCID logo https://orcid.org/0000-0002-0782-3128
Cha, Jung Yul(차정열)
Choi, Yoon Jeong(최윤정) ORCID logo https://orcid.org/0000-0003-0781-8836
Han, Sang Sun(한상선) ORCID logo https://orcid.org/0000-0003-1775-7862
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