Purpose
To evaluate the accuracy of the maxillary segment positioning method using a splint fabricated by computer-aided design/computer-aided manufacturing (CAD/CAM) and surgical navigation in patients who required two-jaw surgery.
Methods
Subjects were 35 patients requiring two-jaw surgery. A 3-dimensional (3D) skull model was prepared using cone-beam computed tomography (CBCT) data and dentition model scan data. Two-jaw surgery was simulated using this model, and a splint for maxillary positioning was fabricated by CAD/CAM. Using coordinate transformation software, the coordinate axis of surgical simulation data was merged with the navigation system, and data were imported to the navigation system. The maxillary segment was placed using the CAD/CAM splint, and consistency of the maxillary segment position with that planned by simulation was confirmed using the navigation system. CBCT taken at 4 weeks postoperatively and the prediction image fabricated using surgical simulation were superimposed. Predicted movement distances (PMD) at 6 arbitrary measurement points and actual movement distance (AMD) in surgery were measured. Differences of 3D measurements between the surgical simulation and postoperative results were evaluated.
Results
No significant differences were seen between PMD and AMD at most measurement points on the X and Y axes. Although significant differences between PMD and AMD were seen on the Z axis, no difference was evident between linear distance on the estimated image and postoperative CBCT image at most measurement points in 3D space. Mean error at measurement points between the PMD and AMD ranged from 0.57 mm to 0.78 mm on the X axis, 0.64 mm–1.03 mm on the Y axis, and 0.84 mm–0.90 mm in the Z axis.
Conclusion
Position of the maxillary segment moved by the CAD/CAM splint in Le Fort I osteotomy was almost consistent with the position established by simulation using the navigation system, confirming clinical accuracy.
We performed surgical simulation using plaster models prior to actual orthognathic surgery in patients with jaw deformity. In this study, to achieve more accurate positioning of bone segments during surgical simulation, maxillofacial computed tomography(CT)images and three-dimensional(3D)dentition model images were integrated in order to produce maxillofacial models with detailed dentition. Two adult patients with jaw deformity were selected for this study. The methods were as follows : 1)production of ceramic ball-attached reference splints, 2)acquisition of facial skeletal information from X-ray CT, 3)acquisition of dentition model information from X-ray micro-CT, 4)3D image integration of facial skeletal information and dentition model information using reference splints for positioning, 5)production of a facial skeletal model using rapid prototyping, and 6)surgical simulation using the model produced. 3D imaging of jaw morphology and model production in each case was performed for more accurate surgical simulation. A comparison between the models after simulation and postoperative CT images was useful for feedback from oral surgeons. Furthermore, it became possible to give a more precise explanation to patients, and consistency between expected postoperative morphology and patients' esthetic requests was achieved. The results suggest that the production of models reflecting detailed dentition information can be a useful tool in orthognathic surgery.: orthognathic surgery(顎矯正手術) ,surgical simulation(手術シミュレーション) ,rapid prototyping(三次元造形法) [Received Oct. 19, 2012] 顎変形症における顎矯正手術では,従来セファログラム や歯列石膏模型を用いた術前計画や手術シミュレーション が行われてきた。近年では,CT 画像解析ソフトウェアの 普及に伴い,コンピュータ画面上での三次元診断や手術シ ミュレーションが可能となり,その有用性が報告されてい る 1, 2) 。しかし,顎変形症患者の顎顔面骨格の複雑な三次元 形態を二次元ディスプレイで正確に把握することは困難で あり,画像から離断部位を詳細に決定するのは不可能であ る。また,画像上で離断した骨片を 6 自由度で正確に動か すためには,高度な画像処理技術が必要となる。そのため, 顎矯正手術時における骨片の干渉部位やその程度,骨片の 変位量などを画像上で正確に特定することは困難である。 そのような背景から,三次元造型機を用いて作製された 実体モデルを用いたサージェリーシミュレーションが報告 されてきた 3-5) 。以前は光硬化樹脂を使用したモデルが多 く用いられていたが,最近では切削感覚が骨に近く,より 1) 昭和大学歯学部歯科矯正学教室(主任:槇 宏太郎教授) 2) 昭和大学歯学部顎口腔疾患制御外科学教室(主任:新谷 悟教授)
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