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Radiographic evaluations of molar intrusion and changes with or without retention in rats

 Yoon Jeong Choi  ;  Kyung-Ho Kim  ;  Kee-Joon Lee  ;  Chooryung J. Chung  ;  Young-Chel Park 
 ANGLE ORTHODONTIST, Vol.81(3) : 389-396, 2011 
Journal Title
Issue Date
Alveolar Process/diagnostic imaging ; Alveolar Process/physiopathology ; Animals ; Male ; Maxilla ; Molar*/diagnostic imaging ; Molar*/physiopathology ; Open Bite/therapy* ; Orthodontic Retainers ; Radiography ; Rats ; Rats, Sprague-Dawley ; Root Resorption/diagnostic imaging ; Root Resorption/etiology* ; Secondary Prevention ; Tooth Movement Techniques/adverse effects ; Tooth Movement Techniques/instrumentation ; Tooth Movement Techniques/methods* ; Tooth Root/diagnostic imaging
Molar intrusion ; Retention ; Miniscrew ; Openbite
OBJECTIVE: To describe radiographic changes caused by molar intrusion with or without retention methods in rats.

MATERIALS AND METHODS: Thirty 12-week-old male rats were assigned to six groups (n  =  5 each). Molar intrusion was achieved with an intrusion spring to two maxillary molars for 2 weeks. The control group underwent the same experimental conditions, but without the intrusion spring. The intrusion and control groups were then euthanized. In four groups, the intrusion spring was disengaged after intrusion and the new molar positions were either retained or not with an occlusal bite-block for 1 or 2 weeks. Radiographic changes were measured in the cusp tip, root apices, and alveolar crests.

RESULTS: After 2 weeks of intrusion, the cusp tip and root apices had moved apically compared with the control group. However, the alveolar crests were similar in the intrusion and control groups. With retention bite-block, the new position of the intruded cusp tip was maintained, but the root apices had moved occlusally, and the alveolar crest between the two intruded molars had moved apically. Without retention, the cusp tip and root apices had moved occlusally, and the alveolar crest between the intruded molar and unintruded molars had moved occlusally compared with the intrusion group.

CONCLUSION: Rat molars were successfully intruded and maintained at the altered position with retention bite-block. However, the apical root resorption was observed as an instant response. The alveolar crest adjacent to the intruded molars was repositioned apically, but that was a delayed response compared to root resorption.
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2. College of Dentistry (치과대학) > Dept. of Orthodontics (교정과학교실) > 1. Journal Papers
Yonsei Authors
Kim, Kyung Ho(김경호) ORCID logo https://orcid.org/0000-0002-8154-2041
Park, Young Chel(박영철)
Lee, Kee Joon(이기준) ORCID logo https://orcid.org/0000-0002-0782-3128
Chung, Chooryung J.(정주령) ORCID logo https://orcid.org/0000-0001-9399-7193
Choi, Yoon Jeong(최윤정) ORCID logo https://orcid.org/0000-0003-0781-8836
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