PubMed · 2259811
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G Grinspon, J Learreta. 1990. [Visualized treatment objective: a simplified technique].. https://pubmed.ncbi.nlm.nih.gov/2259811/
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Facial reconstruction using 3-D computer graphics is being used in our institute as a routine procedure in forensic cases as well as for skulls of historical and archaeological interest. Skull and facial data from living subjects is acquired using an optical laser scanning system. For the production of the reconstructed image, we employ facial reconstruction software which is constructed using the TCL/Tk scripting language, the latter making use of the C3D system. The computer image may then be exported to enable the production of a solid model, employing, for example, stereolithography. The image can also be modified within an identikit system which allows the addition of facial features as appropriate.
The introduction of digital X-ray techniques offered a variety of new possibilities for digital image enhancement and exposure reduction. In order to compare the reproducibility of cephalometric landmarks on conventional and digital lateral headfilms 100 digital and 100 conventional lateral headfilms of patients attending our clinic were randomly selected. The digital cephalograms were obtained using storage phosphor plates in standard X-ray cassettes. All X-rays had been taken at 77 kV. For the digital images the mAs settings for conventional images minus 4 mAs were used. Two orthodontists traced each X-ray twice (21 reference points) at an interval of at least 1 week. The tracings were superimposed and the distances between the tracings of identical reference points were registered. The average reproducibility of cephalometric landmarks was significantly higher on the digitally obtained images, despite a reduction of radiation exposure of 23.7% in the digital images.
Computed tomography (CT)-based anatomic three-dimensional (3D) models have become important tools in oral maxillofacial surgery. There are three problems involved in the precise transfer of the experience gained and the results of simulation surgery to the patient: (1) 3D models have no precise reference points; (2) it is difficult to measure translations three-dimensionally; and (3) exact transfer to the patient intraoperatively is impossible. We have introduced a new system which solves these problems. In the first step 3D dental arches are replaced by plaster models, using an occlusal device with three radioopaque hemispheres as reference. A computerised electromagnetic tracker makes 3D measurements possible during simulated surgery, and a newly developed transfer system with a neurosurgical head frame to provide stable anchorage is used for positioning during surgery. We present our experience with this system in 15 orthognathic patients undergoing bimaxillary surgery. With the 3D computerised simulation surgery and model operation transfer system (3D-COSMOS) the dental arches can be replaced with a mean accuracy of 0.03 mm. The 3D translations of jaw segments can be measured precisely (0.11 mm) and simultaneously at the osteotomy line and the teeth. The new jaw position is transferred mechanically with a precision of 0.05 mm. Operation time is prolonged only by 15 min.