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Background
Orthognathic surgery is a powerful tool for directly reshaping the bony architecture of the facial skeleton, and indirectly affecting the soft tissue envelope of the neck and face. Traditional presurgical planning is complex and requires bite molds, wax bites, and the prefabrication of an occlusal splint. These techniques may be less familiar to the plastic surgeon without a background in dentistry. Operative reimbursement infrequently covers the prolonged labor and measurement costs incurred in the surgical planning. As a response to this, we report our use of the computer-assisted surgical simulation (CASS) modeling system in preoperative planning and splint fabrication, and the significant reduction in our overall preoperative time.
Methods
Bite registration with a bite jig and fast curing bisacryl bite registration material was used to record detailed occlusal anatomy. Upper, followed by lower bite registrations were sequentially created on a single bite jig, which was then mounted to a fiducial-based facebow for facial skeleton indexing. Indexing was done with standard Euler angles (pitch, yaw, and roll) based on accelerometer readings for the head in a normal resting position. The data was submitted and CAD/CAM occlusal splints were fashioned and returned to the senior surgeon.
Results
Between September 2010 and January of 2011, a total of 10 consecutive patients were enrolled in the study. Indications for surgery included 6 LeFort I advancements, and 4 combined LeFort I/BSSO cases. Average time for bite registration was 10min16s ± 1min33s, with an additional 8min6s ± 4min45s needed for CASS modeling and virtual splint confirmation. 6 patients required cephalometric tracings, for an additional 12min50s ± 1min10s. Average total session time for all patients was 26min4s ± 9min13s.
Conclusion
Orthognathic modeling requires intricate preoperative planning in order to create accurate surgical splints. Computer-assisted surgical simulation (CASS) modeling has significantly decreased the time devoted to preoperative splint fabrication and has facilitated splint fabrication in orthognathic surgery. The use of CASS has markedly decreased preoperative office splint planning and fabrication time, and thus, has had a positive impact on reimbursement for orthognathic surgery.
Figure 1. Left, Application of the bisacryl bite registration material to the bite jig. Right,
Upper and lower occlusal registrations.
Figure 2. Left, Once occlusal registrations were completed, the bite jig was mounted to the fiducial-based facebow for facial skeleton indexing. Right, Standard Euler angles created with the facebow.