Virtual Surgical Planning for Orthognathic Surgery Using Digital Data Transfer and an Intraoral Fiducial Marker: The Charlotte Method

Abstract

We describe an alternative workup protocol for virtual surgical planning of orthognathic surgery using an intraoral fiducial marker, clinical photography, and the digital transfer of occlusal data. Wealso discuss our initial experience using this protocol in a series of patients. A retrospective cohort study was performed of consecutive patients who had undergone combined maxillary and mandibular osteotomies for the correction of dentofacial deformities at 1 center. These patients underwent treatment planning using the modified virtual surgical planning protocol described in the present report. The primary outcome evaluated was the accuracy of the method, which was determined through superimposition of the surgical plan to the postoperative cone-beam computed tomography (CBCT) scan. The secondary outcomes included the accuracy of the natural head position readings and the adequacy of the CBCT scanned stone models for the fabrication of occlusal splints. The population included 25 patients. The root mean standard deviation (RMSD) from the preoperative plan to the postoperative scan at the maxillary cephalometric points was 1.2, 1.4, and 2.1mm in the axial, sagittal, and coronal planes, respectively. The RMSD of the superimposed plan to the postoperative scan at the 3 mandibular cephalometric points was 1.2, 0.8, and 0.7mm in the axial, sagittal, and coronal planes, respectively. The average variance from the axial, sagittal, and coronal planes for the natural head position was 0.05, 2.22, and 0.69 mm, respectively. All splints fabricated from the CBCT occlusal data fit the stone models and were used intraoperatively. In the subset of patients whose models were both digitally transferred and laser scanned, the superimposition of the laser scan data to the CBCT scanned data was found to have a maximum variation of 0.2mm at the occlusal level. The use of an intraoral fiducial marker changed the workflow for the data collection needed for virtual surgical planning of the correction of dentofacial deformities, while still obtaining accurate results. Because the device does not cause lip distortion, the possibility of virtually predicting a more expectant postoperative lip position exists without the need for additional scans. Furthermore, this work flow allows the transfer of data to be isolated to digital media.