Korean J Orthod.  2013 Feb;43(1):42-52. 10.4041/kjod.2013.43.1.42.

New bimaxillary orthognathic surgery planning and model surgery based on the concept of six degrees of freedom

• Jeon J
• Kim Y
• Kim J
• Kang H
• Ji H
• Son W

• KMID: 2273468
• DOI: http://doi.org/10.4041/kjod.2013.43.1.42

Abstract

The aim of this paper was to propose a new method of bimaxillary orthognathic surgery planning and model surgery based on the concept of 6 degrees of freedom (DOF). A 22-year-old man with Class III malocclusion was referred to our clinic with complaints of facial deformity and chewing difficulty. To correct a prognathic mandible, facial asymmetry, flat occlusal plane angle, labioversion of the maxillary central incisors, and concavity of the facial profile, bimaxillary orthognathic surgery was planned. After preoperative orthodontic treatment, surgical planning based on the concept of 6 DOF was performed on a surgical treatment objective drawing, and a Jeon's model surgery chart (JMSC) was prepared. Model surgery was performed with Jeon's orthognathic surgery simulator (JOSS) using the JMSC, and an interim wafer was fabricated. Le Fort I osteotomy, bilateral sagittal split ramus osteotomy, and malar augmentation were performed. The patient received lateral cephalometric and posteroanterior cephalometric analysis in postretention for 1 year. The follow-up results were determined to be satisfactory, and skeletal relapse did not occur after 1.5 years of surgery. When maxillary and mandibular models are considered as rigid bodies, and their state of motion is described in a quantitative manner based on 6 DOF, sharing of exact information on locational movement in 3-dimensional space is possible. The use of JMSC and JOSS will actualize accurate communication and performance of model surgery among clinicians based on objective measurements.

Keyword

Wafer; Diagnosis and treatment planning; Surgery

MeSH Terms

Congenital Abnormalities
Dental Occlusion
Facial Asymmetry
Follow-Up Studies
Freedom
Humans
Incisor
Malocclusion
Mandible
Mastication
Orthognathic Surgery
Osteotomy
Osteotomy, Sagittal Split Ramus
Recurrence

Figure

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  Figure 1 Jeon's orthognathic surgery simulator (JOSS). In order to reposition maxillary and mandibular models in accordance with 6 degrees of freedom, precision stage are layered on each upper and lower part of the simulator and attached to the main frame. A, View of a facebow connected to a bite fork. Joints allow compatibility with various kinds of facebows. B, View of mounting completed.

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  Figure 2 Example of 6 degrees of freedom. Movement of a rigid body in 3-dimensional space is divided into translation parallelto 3 coordinate axes and rotation on 3 axes.

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  Figure 3 Initial records.

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  Figure 4 Presurgical records.

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  Figure 5 Surgery planning. 0-degree of yaw, 7-degree of pitch, 4-degree of roll, 0 mm of lateral translation, 2 mm of backward translation and 1 mm of upward translation of maxilla were planned. A, Surgical treatment objective (STO) on lateral cephalogram; B, STO on posteroanterior cephalogram; C, STO on computed tomography.

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  Figure 6 Construction of Jeon's model surgery chart. Amount of movement with each 6 degrees of freedom were recorded. PA, Posteroanterior.

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  Figure 7 Model surgery using Jeon's orthognathic surgery simulator. A, Mounting was completed; B, maxillary model was vertically moved 10 mm upward; C, yaw, roll and pitch correction was done. Rotational correction caused unwanted displacement of MPIE; D, MPIE was moved back to pre-operational position; E, three types of translation was done; F, before model surgery; G, after model surgery.

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  Figure 8 Postsurgical records.

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  Figure 9 Superimposition of surgical treatment objective (STO) and results of real surgery.

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  Figure 10 Retention results after 1 year.

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