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Laser 반사측정법을 이용한 전치부 후방 견인시 치조골 높이와 치근길이 감소에 따른 저항중심의 위치변화에 관한 연구

Other Titles
 A study about the change of locations of the center of resistance according to the decrease of alveolar bone heights and root lengths during anterior teeth retraction using the laser reflection technique 
Authors
 민영규  ;  황충주 
Citation
 Korean Journal of Orthodontics (대한치과교정학회지), Vol.29(2) : 165-181, 1999 
Journal Title
 Korean Journal of Orthodontics (대한치과교정학회지) 
ISSN
 2234-7518 
Issue Date
1999
Keywords
Photodetector ; laser reflection technique ; center of resistance ; alveolar bone height ; root length ; crown-to-root ratio ; lever and pulley
Abstract
Treatment mechanics should be individualized to be suitable for each patient`s personal teeth and anatomic environment to get a best treatment result with the least harmful effects to teeth and surrounding tissues. Especially, the change of biomechanical reaction associated with that of the centers of resistance of teeth should be considered when crown-to-root ratio changed due to problematic root resorption and/or periodontal disease during adult orthodontic treatment. At the present study in order to investigate patterns of initial displacements of anterior teeth under certain orthodontic force when crown-to-root ratio changed in not only normal periodontal condition but also abnormal periodontal and/or teeth condition, the changes of the centers of resistance for maxillary and mandibular 6 anterior teeth as a segment were studied using the laser reflection technique, the lever&pulley force applicator and the photodetector with these quantified variables reducing alveolar bone 2mm by 2mm for each of maxillary 6 anterior teeth until the total amount of 8mm and root 2mm for each of mandibular 6 anterior ones until the total amount of 6mm. The results were as follows: 1. Under unreduced condition, the center of resistance during initial displacement of maxillary 6 anterior teeth was located at the point of about 42.4% apically from cemento-enamel junction(CEJ) of the averaged tooth of them and kept shifting to about 76.7% with alveolar bone reduction. 2. The distance from the averaged alveolar crest level of maxillary 6 anterior teeth to the center of resistance for the averaged tooth of them kept decreasing with alveolar bone reduction, but the ratio to length of the averaged root embedded in the alveolar bone was stable at around 33% regardless of that. 3. Under unreduced condition, the center of resistance during initial displacement of mandibular 6 anterior teeth was located at the point of about 43% apically from CEJ of the averaged tooth of them and this ratio kept increasing tc about 54% with root reduction. Bur the distance from CEJ to the center of resistance decreased from around 5.3mm to around 3.3mm, that is to say, the center of resistance kept shifting toward CEJ with the shortening of root length. 4. A unit reduction of alveolar bone had greater effects on the change of the centers of resistance than that of root did during initial phase of each reduction. But both of them had similar effects at the middle region of whole length of the averaged root.
Files in This Item:
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Appears in Collections:
2. College of Dentistry (치과대학) > Dept. of Orthodontics (교정과학교실) > 1. Journal Papers
Yonsei Authors
Hwang, Chung Ju(황충주) ORCID logo https://orcid.org/0000-0003-3024-4551
URI
https://ir.ymlib.yonsei.ac.kr/handle/22282913/173872
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