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KJO Korean Journal of Orthodontics

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pISSN 2234-7518
eISSN 2005-372X
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Korean J Orthod

Published online January 21, 2021

Copyright © The Korean Association of Orthodontists.

Mandibular skeletal posterior anatomic limit for molar distalization in patients with Class III malocclusion with different vertical facial patterns

Sung ho Kima Kyung suk Chab Jin woo Leec Sang min Leed

Department of Orthodontics, Dankook University, Cheonan, Korea.

Correspondence to:Kyung suk Cha, Department of Orthodontics, Dankook University Dental Hospital, 119, Dandae ro, Dongnam gu, Cheonan, Chungnam, 330 714, Korea; Email kscha-1234@daum.net Tel : 82 10 2221 8514 , Fax : 82 41 550 2233

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective: The aim of this study was to compare the differences of the mandibular posterior anatomic limit (MPAL) distances stratified by vertical patterns in skeletal Class III malocclusions using cone-beam computed tomography (CBCT).
Methods: CBCT images of 48 skeletal Class III patients (mean age, 22.8 ± 3.1 years), stratified by the vertical pattern (hypodivergent, normodivergent, and hyperdivergent) groups of 16 were analyzed. While parallel to posterior occlusal line, the shortest linear distances from the distal root of mandibular second molar to the inner cortex of mandibular body were measured at depths of 4, 6, 8 mm (D4,6,8mm) from cementoenamel junction. The MPAL distances were compared between the hypodivergent, normodivergent, and hyperdivergent pattern groups and their correlations were analyzed.
Results: There was no significant difference between the mean ages, gender distribution, asymmetry, or crowding of three groups. MPAL distance was significantly longer in males (3.8 ± 2.6 mm) than females (1.8 ± 1.2 mm) at the 8-mm root level. At all root levels, the MPAL distance was significantly different in the hypodivergent and hyperdivergent (p<0.001), as well as between the normodivergent and hyperdivergent group (p<0.01). The MPAL distances were the shortest in the hyperdivergent group. SN-GoGn angle is highly correlated with the MPAL distance at all root levels (p<0.01).
Conclusions: The MPAL distances were shortest in patients with hyperdivergent patterns and had a decreasing tendency as the SN-GoGn angle increased. The MPAL distances were significantly shorter at the 8-mm root level, the most critical root level, which was about 3.16 mm.

Keywords: Class III treatment, CT, Distalization, Alveolar bone housing

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Korean J Orthod

Published online January 21, 2021

Copyright © The Korean Association of Orthodontists.

Mandibular skeletal posterior anatomic limit for molar distalization in patients with Class III malocclusion with different vertical facial patterns

Sung ho Kima Kyung suk Chab Jin woo Leec Sang min Leed

Department of Orthodontics, Dankook University, Cheonan, Korea.

Correspondence to:Kyung suk Cha, Department of Orthodontics, Dankook University Dental Hospital, 119, Dandae ro, Dongnam gu, Cheonan, Chungnam, 330 714, Korea; Email kscha-1234@daum.net Tel : 82 10 2221 8514 , Fax : 82 41 550 2233

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective: The aim of this study was to compare the differences of the mandibular posterior anatomic limit (MPAL) distances stratified by vertical patterns in skeletal Class III malocclusions using cone-beam computed tomography (CBCT).
Methods: CBCT images of 48 skeletal Class III patients (mean age, 22.8 ± 3.1 years), stratified by the vertical pattern (hypodivergent, normodivergent, and hyperdivergent) groups of 16 were analyzed. While parallel to posterior occlusal line, the shortest linear distances from the distal root of mandibular second molar to the inner cortex of mandibular body were measured at depths of 4, 6, 8 mm (D4,6,8mm) from cementoenamel junction. The MPAL distances were compared between the hypodivergent, normodivergent, and hyperdivergent pattern groups and their correlations were analyzed.
Results: There was no significant difference between the mean ages, gender distribution, asymmetry, or crowding of three groups. MPAL distance was significantly longer in males (3.8 ± 2.6 mm) than females (1.8 ± 1.2 mm) at the 8-mm root level. At all root levels, the MPAL distance was significantly different in the hypodivergent and hyperdivergent (p<0.001), as well as between the normodivergent and hyperdivergent group (p<0.01). The MPAL distances were the shortest in the hyperdivergent group. SN-GoGn angle is highly correlated with the MPAL distance at all root levels (p<0.01).
Conclusions: The MPAL distances were shortest in patients with hyperdivergent patterns and had a decreasing tendency as the SN-GoGn angle increased. The MPAL distances were significantly shorter at the 8-mm root level, the most critical root level, which was about 3.16 mm.

Keywords: Class III treatment, CT, Distalization, Alveolar bone housing