探索正畸牙齿移动中出现骨开窗、骨开裂及根吸收的风险因素

The increasing use of Cone Beam Computer Tomography (CBCT) in orthodontics enables clinicians to view, from both the buccal and lingual, the relationship between tooth and alveolar bone. Accordingly, it should be possible to use the CBCT to assess the bony impact of various forms of orthodontic treatment. For example, given this imaging technique, it would be possible to avoid moving a tooth's root/roots out of alveolar bone, especially when absolute (implant) anchorage is employed in "extraction" treatments. Conversely, the claim that non-extraction orthodontic expansion causes alveolar dehiscences and fenestration can be examined in detail. Further, if treatment can cause bony defects, what are the risk factors? The literature has no convincing way of answering these and other biologically important clinical questions. The purpose of this project, therefore, is to establish and apply CBCT diagnostic protocols to the study of such orthodontic sequelae as root resorption and alveolar dehiscence and fenestration. First, we will use 14 cadaver specimens to assess naturally-occurring osseous defects, with actual dissections serving as the gold standard against which the tomographic images will be compared and calibrated. Once the imaging parameters have been optimized, we will use them to explore the influence of orthodontic tooth movement on the underlying bone. To do so, we must measure change, and to measure change, we must employ some form of regional superimposition (the act of aligning one image relative to another to detect change). To this end, we have gathered a unique serial CBCT sample of 15 subjects, each with at least 4 implants in the upper jaw, and will increase to 30 subjects for this project. Given these multiple stable implants, we will be able to identify naturally-occurring bony structures that are stable over time. Based on these data we will be able to develop a three-dimensional CBCT superimposition technique that can be used in un-implanted patients. With this new technique, we will conduct a 3D evaluation of the impact of orthodontic treatment in a third sample, in this case, 30 bicuspid-extraction patients. In addition to the patient's age, sex, and craniofacial morphology, the pattern and amount of orthodontic tooth movement, anchorage type, rate of tooth movement, etc. will be analyzed to explore their relationship to alveolar dehiscence, fenestration and root resorption. This study will be the first to study alveolar dehiscence and fenestration in CBCT diagnosis and, in the process, the first to establish a 3D structural superimposition method based on CBCT images. It will explore the physiologic limit of orthodontic teeth movement and thus serve the health goal of orthodontic treatment.

锥体束CT在口腔正畸学的广泛应用使正畸医师可以从唇颊舌面观察每颗牙齿的牙根与牙槽骨之间的关系，于是不难看到正畸治疗后部分牙根被移至牙槽骨外的影像，尤其是在拔牙病例使用种植钉作为绝对支抗内收前牙及严重拥挤的扩弓等现代正畸技术中。但这是否意味着发生了骨开窗或骨开裂？与正畸牙齿移动之间是什么关系？却未见科学的研究证据。本课题以14例人类湿颅标本为研究对象，通过CBCT检查与解剖直视对比建立牙槽骨开窗、骨开裂的影像学诊断标准；为研究正畸牙齿移动对骨开窗骨开裂的影响，本课题设计了用需要种植钉支抗的病例去寻找CBCT影像上可以用作稳定重叠结构的另一样本，预计30例，去建立三维颅面影像时代的重叠方法，并设计用重叠方法测量三维牙齿移动的软件。该研究将首次建立CBCT诊断骨开窗骨开裂的方法，并创立三维稳定结构重叠的方法及三维牙齿移动评价体系，此两项研究成果将为探索正畸牙齿移动的生理性边界奠定基础。

锥体束CT在口腔正畸学的广泛应用使正畸医师可以从三维层面观察每颗牙齿的牙根与牙槽骨之间的关系，大量的临床信息中可以发现个别正畸治疗后牙根可疑移出牙槽骨界限的情况，牙根的吸收、牙槽骨的可疑缺损更是较多发生在大量内收前牙或扩展牙弓宽度等现代正畸技术中，但影像中的牙槽骨缺损与解剖实际的关系、牙根吸收与牙齿移动的关系却未见科学的研究证据。本课题以14例人类湿颅标本为研究对象，通过CBCT检查与解剖直视对比建立了牙槽骨开窗、骨开裂的影像学诊断标准；为研究正畸牙齿移动对骨开窗骨开裂的影响，本课题收集了具有种植钉标记的治疗前后CBCT资料样本成人20例、青少年15例，通过这些资料建立了三维颅面影像的重叠方法，并设计了用重叠方法测量牙槽骨变化、诊断牙槽骨缺损以及测量三维牙齿移动的方法。该研究首次建立了CBCT诊断骨开窗骨开裂的方法，并创立三维稳定结构重叠的方法及三维牙齿移动评价体系，此两项研究成果将为探索正畸牙齿移动的生理性边界奠定基础。

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