PubMed · 3293174
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T Bormes. 1988. Magnets--myth and magic.. https://pubmed.ncbi.nlm.nih.gov/3293174/
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Reconstruction of segmental mandibular defects resulting from trauma, infection, or tumor resection still remains difficult. Although cosmetic improvement was seen in patients who had immediate reconstruction of the mandibular continuity, normal mastication and deglutition could not be achieved by conventional removable dentures. Since 1988, the treatment protocol has been modified to use endosseous root-form implants to support dental prostheses instead of the conventional removable prostheses in these patients. There are 2 types of prostheses that can be constructed over dental implants: (1) a removable implant overdenture and (2) a fixed detachable prosthesis. Although the latter better meets in patients' psychological needs, it may present problems such as phonetic discrepancies, food impaction, difficult home care, and poor esthetics if the patient has a high lip line. In addition, it is not easy to fabricate accurately in the laboratory. To overcome these problems, a case is presented to illustrate the use of another fixed-type prosthesis, a double-coping technique, for fabricating dentures so that any discrepancy between the inner and outer copings can be filled by cement. The technique not only improves the shortcomings of fixed detachable prostheses but also satisfactorily meets patients' desire for normal mastication and deglutition. Follow-up after 4 years showed no significant changes around the implants by clinical and radiographic examinations.
The use of CT-based intraoperative navigation has greatly improved controlled surgery in many specialties. In this study the precision of the SMN system (Zeiss, Oberkochen, Germany) for navigated drilling and following implantation in the maxilla is evaluated. This study should prove the suitability of navigation systems for computer-assisted implantation in the maxilla to avoid perforation to the maxillary sinus. Therefore 60 target drills were carried out on 10 standardized polyurethane milling models after CT-scanning. The models were produced with cranial open maxillary sinuses. The CT-scans were performed with a slice distance of 1 mm. Then the CT-data were transferred to the workstation of the SMN system (Zeiss, Oberkochen, Germany) and a referenciation of the fiducials for superposition of the native and CT model were done. Referenciation of the model was performed with the aid of a drilling tool. This drilling tool was used for later navigation-assisted drilling into the upper jaw. The target of drilling was the maxillary sinus floor. The aim was to come as near as possible without perforation. The distance of the bottom of the drilling holes to the maxillary sinus floor were measured after section of the model. An average drilling depth of 6.97 mm (s=0.4) and a mean distance to sinus floor of 0.11 mm (s=0.2) was found. In 13 cases the lower board of sinus was perforated.In conclusion a high precision of CT-based navigation for controlled preimplantological drilling was seen.
Development of complex software applications in image guided therapy (IGT) is often complicated by the fact that providing basic functionality for image processing and user interaction from a graphical user interfaces (GUI) requires considerable manpower for software development. We present a programming environment that combines the high-level image processing library AVW, in-house developed patient-to-image registration procedures, and an interface to position measurement hardware. A specific application can be developed by using Tcl/Tk, a simple platform-independent scripting language, for GUI development. This environment was applied to developing VISIT, a navigation system for computer-aided implant dentistry. VISIT is presented as a result of this paper. Parts of the development environment were made accessible to the public. Future work includes the implementation of video input for connecting ultrasound or fluoroscopy units. We conclude that our approach is well suited to accelerate the development of exploratory new applications of IGT.