A computed tomographic(CT) image study on the thickness of the infrazygomatic crest of the maxilla and its clinical implications for miniscrew insertion
INTRODUCTION: The purpose of this study was to measure the thickness of the infrazygomatic (IZ) crest above the maxillary first molar at different angles and positions to the maxillary occlusal plane.(解剖位置在上顎第一大臼齒附近)
These measurements were then used to derive clinical implications and guidance for inserting miniscrews in the IZ crest
without injuring the mesiobuccal root of the maxillary first molar. (要注意勿傷及第一大臼齒的近心頰側牙根)
METHODS: Computed tomographic images of 16 adults were used. For each subject, on the coronal slice of the computed tomographic image containing the IZ crest and mesiobuccal root of the maxillary first molar, the IZ crest thickness and the miniscrew insertion position were measured by postulating that the miniscrew would be inserted at each 5 degrees increment from 40 degrees to 75 degrees to the maxillary occlusal plane.(他以每次5度的角度去做電腦斷層造影,,從40~75度間去做)
RESULTS: The IZ crest thickness above the maxillary first molar ranged from 5.2 +/- 1.1 mm to 8.8 +/- 2.3 mm(得到IZC的臨床厚度), measured at 40 degrees to 75 degrees to the maxillary occlusal plane and 13 to 17 mm above the maxillary occlusal plane.
CONCLUSIONS: By adopting 6 mm as the minimal IZ crest thickness for sustaining a miniscrew well throughout treatment and avoiding injury to the mesiobuccal root of the maxillary first molar, the clinical implication for miniscrew placement in the IZ crest of an adult is to insert it 14 to 16 mm above the maxillary occlusal plane and the maxillary first molar at an angle of 55 degrees to 70 degrees to the maxillary occlusal plane. (植入IZC的臨床建議)
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