Influence of Mandibular Deformity to Cranio-Facial Growth Evaluated by 3-D Cephalometry

与常规X线片相比，三维CT具有对面部复杂解剖结构进行三维分析的优势。在CRT上使用切割功能可以观察和测量颌面部骨骼任何方向和内部结构的三维图像，由CT图像重建的STL模型(塑料实体模型)使面部骨骼的三维分析变得更加容易。本研究的目的是比较三维CT图像和STL模型的测量精度，并将STL模型的测量应用于临床病例，分析下颌畸形对颅面部周围解剖结构的影响。在干燥颅骨上制作了三维CT图像和三维模型，并对测量精度进行了比较，并将三维CT模型和整形模型应用于3例临床病例(冠突增生症2例，关节强直1例)。结果表明，整形模型的测量精度明显优于…模型在CRT上测量精度的差异可能是由于CRT上三维图像中测量点的确定困难所致。STL模型的三维分析比常规的二维分析(头影测量分析)更容易，使测量二维头影测量不可能的点成为可能。弹性材料(DeSolite SCR 301)单体的比重。日本口香糖株式会社)在树脂中为1.08 DM和1.15 DP。聚合物线性收缩的体积收缩为-6.09%，线性收缩为-2.03%。在临床病例中，塑料模型使近距离观察复杂的解剖关系成为可能，这些关系在轴位CT图像上甚至在三维CT图像上很容易被忽视。整形模型复制了颧骨内表面的外生骨瘤，面对延长的突起的凹陷，暗示了患者三叉肌的直接功能原因。在TMJ强直的病例中，冠突已经延长的事实表明，延长可能是由于存在的邻近骨畸形引起的三叉肌导致的肌肉张力。一般认为，即使在不太严重的冠突增生症中，冠突也会与颧骨接触，从而在存在颅面畸形的情况下导致三叉症。较少

3-D CT has the advantage to analyze the complex anatomical structures of the facial bones three-dimensionally compared with conventional radiograph. Observation and the measurement of 3-D image in any directions and inner structures of maxillofacial bones using cutting functions are possible on CRT.STL model (plastic actual model) reconstructed from CT images makes 3-D analysis of the facial bones easier. The aims of this study is to compare 3-D CT images and STL model in measurement accuracy and apply the measurement on STL model in the clinical cases to analyze the influence of mandibular deformity to the surrounding anatomical structure in the cranio-facial region. 3-D CT images and STL models were made in a dry skull and measurement accuracy was compared, Furthermore we applied 3-D CT and plastic models in three clinical cases (Coronoid process hyperplasia 2 cases, TMJ ankylosis 1 case) Our results showed the measurement accuracy on the plastic model was notably superior to that of … More the 3-D images on CRT.The difference in measurement accuracy might be due to the difficulty determining The measurement points in the 3-D images on CRT.3-D analysis on STL model was more easier than the ordinal 2-D analysis (cephalometry analysis) and made it possible to measure the points which is not possible on 2-D cephalometry. The specific gravity of the monomer of the pjastic material (Desolite SCR 301. Japan Gum Co. Ltd.) was 1.08 Dm and 1.15 Dp in resin. Volume shrinking was a -6.09% and -2.03% in linear shrinking by polyimerisation. ln clinical cases, plastic models made it possible to (10 close observation of the complex anatomical relationship which are easily overlooked on axial CT images and even on 3-D CT images. The plastic model duplicated the exostosis of the inner surface of the malar bone facing the concavity of the elongated process suggesting the direct functional cause of the patient's trismus. The fact that the coronoid process has been elongated in the case with TMJ ankylosis suggests that elongation could occur by the existed neighbouring bone deformity causing trismus lead to the muscle tension. It is thought that even in less extreme cases of coronoid process hyperplasia the processes can come into contact with the malar bones, thus causing trismus when the craniofacial deformity has existed. Less