Department of Orthodontics, School of Dentistry, University of North Carolina, Chapel Hill, NC 27599-7450, USA.
Am J Orthod Dentofacial Orthop. 2011 Sep;140(3):433-43. doi: 10.1016/j.ajodo.2011.01.020.
To understand orthodontic tooth movement, a method of quantification of tooth position discrepancies in 3 dimensions is needed. Brackets and wires now can be fabricated by CAD/CAM technology on a setup made at the beginning of treatment, so that treatment should produce a reasonably precise duplicate of the setup. The extent of discrepancies between the planned and actual tooth movements can be quantified by registration of the setup and final models. The goal of this study was to evaluate the accuracy of a CAD/CAM lingual orthodontic technique.
Dental casts of 94 consecutive patients from 1 practice, representing a broad range of orthodontic problems, were scanned to create digital models, and then the setup and final models for each patient were registered individually for the maxillary and mandibular dental arches. Individual tooth discrepancies between the setup and actual outcome were computed and expressed in terms of a six-degrees-of-freedom rectangular coordinate system.
Discrepancies in position and rotation between the setup and outcome were small for all teeth (generally less than 1 mm and 4°) except for the second molars, where some larger discrepancies were observed. Faciolingual expansion in the posterior teeth was greater in the setup than in the final models, especially at the second molars. Linear mixed models showed that age, type of tooth, jaw, initial crowding, time in slot-filling wire, use of elastics, days in treatment, interproximal reduction, and rebonding, were all influences on the final differences, but, for most of these factors, the influence was small, explaining only a small amount of the discrepancy between the planned and the actual outcomes.
These fully customized lingual orthodontic appliances were accurate in achieving the goals planned at the initial setup, except for the full amount of planned expansion and the inclination at the second molars. This methodology is the first step toward understanding and measuring tooth movement in 3 dimensions.
为了理解正畸牙齿移动，需要有一种方法来量化三维空间中的牙齿位置差异。现在，通过 CAD/CAM 技术可以在治疗开始时制作的设置中制造支架和弓丝，因此治疗应该产生与设置相当精确的副本。通过注册设置和最终模型，可以量化计划和实际牙齿移动之间的差异程度。本研究的目的是评估 CAD/CAM 舌侧正畸技术的准确性。
从一个实践中连续扫描了 94 名患者的牙模，以创建数字模型，然后为每个患者的上颌和下颌牙弓单独注册设置和最终模型。计算了设置和实际结果之间的各个牙齿差异，并以六自由度矩形坐标系表示。
除了第二磨牙，所有牙齿的位置和旋转差异都很小（通常小于 1 毫米和 4°），但观察到一些较大的差异。在设置中，后牙的颊舌扩张大于最终模型，尤其是在第二磨牙。线性混合模型表明，年龄、牙齿类型、颌骨、初始拥挤、槽满丝时间、橡皮圈使用、治疗天数、邻面减径、重粘，这些因素都对最终差异有影响，但对于大多数这些因素，影响很小，只解释了计划和实际结果之间差异的一小部分。
这些完全定制的舌侧正畸矫治器在实现初始设置时的目标方面非常准确，除了计划的完全扩张量和第二磨牙的倾斜度。这种方法是理解和测量三维牙齿运动的第一步。
