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The Use of a Wax Bite Wafer and a Double Computed Tomography Scan Procedure to Obtain a Three-Dimensional Augmented Virtual Skull Model

Swennen, Gwen R. J. MD, LDS, DMD, PhD*; Mommaerts, Maurice Y. MD, LDS, DMD, FEBOMFS, PhD*; Abeloos, Johan MD, LDS, DMD, FEBOMFS*; De Clercq, Calix MD, LDS, FEBOMFS*; Lamoral, Philippe MD, LDS*; Neyt, Nathalie MD, LDS*; Casselman, Jan MD, PhD; Schutyser, Filip MSc

Journal of Craniofacial Surgery: May 2007 - Volume 18 - Issue 3 - p 533-539
doi: 10.1097/scs.0b013e31805343df
Original Articles

A detailed visualization of the interocclusal relationship is essential in a three-dimensional virtual planning setup for orthognathic and facial orthomorphic surgery. The purpose of this study was to introduce and evaluate the use of a wax bite wafer in combination with a double computed tomography (CT) scan procedure to augment the three-dimensional virtual model of the skull with a detailed dental surface. A total of 10 orthognathic patients were scanned after a standardized multislice CT scanning protocol with dose reduction with their wax bite wafer in place. Afterward, the impressions of the upper and lower arches and the wax bite wafer were scanned for each patient separately using a high-resolution standardized multislice CT scanning protocol. Accurate fitting of the virtual impressions on the wax bite wafer was done with surface matching using iterative closest points. Consecutively, automatic rigid point-based registration of the wax bite wafer on the patient scan was performed to implement the digital virtual dental arches into the patient's skull model (Maxilim, version 2.0; Medicim NV, St-Niklaas, Belgium). Probability error histograms showed errors of ≤0.16 mm (25% percentile), ≤0.31 mm (50% percentile), and ≤0.92 (90% percentile) for iterative closest point surface matching. The mean registration error for automatic point-based registration was 0.17 ± 0.07 mm (range, 0.12-0.22 mm). The combination of the wax bite wafer with the double CT scan procedure allowed for the setup of an accurate three-dimensional virtual augmented model of the skull with detailed dental surface. However, from a clinical workload, data handling, and computational point of view, this method is too time-consuming to be introduced in the clinical routine.

From the *Division of Maxillo-Facial Surgery, Department of Surgery and the Department of Radiology and Medical Imaging, General Hospital St-Jan Bruges, Ruddershove, Bruges, Belgium; and Medical Image Computing (Radiology-ESAT/PSI), Faculties of Medicine and Engineering, University Hospital, Gasthuisberg, Leuven, Belgium.

Address correspondence and reprint requests to Gwen R. J. Swennen, MD, LDS, DMD, PhD, Division of Maxillo-Facial Surgery, Department of Surgery, General Hospital St-Jan Bruges, Ruddershove 10, 8000 Bruges, Belgium; E-mail:

This work was partially supported by the Flemish government by grant IWT-040310.

© 2007 Mutaz B. Habal, MD