The aim of this study was to present a new approach to acquire a three-dimensional virtual skull model appropriate for orthognathic surgery planning without the use of plaster dental models and without deformation of the facial soft-tissue mask. A "triple" cone-beam computed tomography (CBCT) scan procedure with triple voxel-based rigid registration was evaluated and validated on 10 orthognathic patients. First, the patient was scanned vertically with a wax bite wafer in place (CBCT scan No1). Second, a limited dose scan of the patient with a Triple Tray AlgiNot impression in place was carried out (CBCT scan No2). Finally, a high-resolution scan of the Triple Tray AlgiNot impression was done (CBCT scan No3). Sequential and semiautomatic triple voxel-based rigid registration (RNo1-RNo3) was performed to augment the patient's skull model with accurate occlusal and intercuspidation data (Maxilim, version 2.1.1., Medicim NV, Mechelen, Belgium). All registrations were based on the Maximisation of Mutual Information registration algorithm. Because the accuracy and stability of the voxel-based registration (RNo1) between the Triple Tray AlgiNot impression scan and the limited low-dose patient scan were not known, this particular registration step needed to be validated. The accuracy of registration was measured on a synthetic skull and showed to be highly accurate. A volume overlap of 98.1% was found for registered impression scan No1. The mean distance between registered impression scan No1 and registered impression scan No2 was 0.08 +/- 0.03 mm (range, 0.04-0.11 mm). As far as the stability of registration was concerned, successful registration with a stable optimal position was obtained with a maximum variability of less than 0.1 mm. The results of this study showed that semiautomatic sequential triple voxel-based rigid registration of the triple CBCT scans augmented the 3-D virtual skull model with detailed occlusal and intercuspidation data in a highly accurate and robust way. The method is therefore appropriate and valid for 3-D virtual orthognathic surgery planning in the clinical routine.

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The aim of this study was to clinically and radiographically evaluate peri-implant bone level changes after rehabilitation of a fully edentulous maxilla by placement of six implants in either fresh extraction sites or healed edentulous ridges up till 18 months after implant placement. Twenty patients with a terminal dentition in the maxillae (11 men, 9 women) received a total of 120 OsseoSpeed® implants; 118 implants could be loaded immediately of which 59 were placed in extraction sockets and 59 were placed in healed sites. Within 24 h after surgery, all patients received a chairside-assembled, fibrereinforced temporary fixed prosthetic reconstruction in occlusion. Six months post-surgery, final screw-retained CoCr (15) or Ti (5) computer numerical control-milled and acrylic-veneered frameworks were placed directly at implant level without interposing abutments. Intraoral radiographs were taken 6 and 18 months after implant placement. Implant survival rate was 100%. Mean marginal bone level was located on average −0.35 mm below the reference point (standard deviation 0.29, range −1.20 to +0.02 mm) 18 months after loading. Whether implants were placed in healed bone sites or fresh extraction sockets did not significantly affect the bone level changes. Furthermore, the use of either CoCr or Ti at the implant level did not significantly affect marginal bone loss. Within the limits of this prospective clinical trial, results seem to indicate that immediate placement and occlusal loading of five to six implants in the edentulous maxilla can be carried out successfully. Whether or not those implants are placed in fresh extraction sockets does not seem to alter the outcome. The present data show a successful 1-year outcome of a treatment protocol involving tooth extraction immediately combined with implant placement and loading.

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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 < or =0.16 mm (25% percentile), < or =0.31 mm (50% percentile), and < or =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.

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