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

与传统x线摄影相比，三维CT具有三维分析面部骨骼复杂解剖结构的优势。在CRT上可以使用切割功能观察和测量任何方向的三维图像和颌面骨的内部结构。由CT图像重建的STL模型（塑性实物模型）使面部骨骼的三维分析更加容易。本研究的目的是比较三维CT图像与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区周围解剖结构的影响。对3例临床病例（冠状突增生2例，颞下颌关节强直1例）应用三维CT和塑料模型进行测量，结果表明，塑料模型的测量精度明显优于CRT上的三维图像。测量精度的差异可能是由于在crt上三维图像中测点的确定困难，STL模型的三维分析比普通二维分析（头测分析）更容易，并且可以测量二维头测无法测量的点。塑料材料（索利特SCR 301）的单体比重。日本树胶株式会社)树脂为1.08 Dm, 1.15 Dp。聚合线性收缩的体积收缩率分别为-6.09%和-2.03%。在临床病例中，塑料模型可以近距离观察复杂的解剖关系，这在轴向CT图像甚至三维CT图像上很容易被忽视。该塑料模型复制了颧骨内表面面向拉长突凹的外植骨，提示患者牙锁的直接功能原因。在TMJ强直病例中，冠突被拉长的事实表明，延长可能是由存在的邻近骨畸形引起的咬合导致肌肉紧张。据认为，即使在不太极端的冠突增生病例中，冠突也可能与颧骨接触，从而在颅面畸形存在时引起咬合。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