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ePaper created 2016-11-03, 14:26:44 | version 1.38.0
Only a few years ago, the idea of using CAD/CAM to fabricate remov- able dentures seemed scarcely real- istic even though such technologies had already become an indispen- sable component of the workflow for fixed superstructures on natural teeth and implants. Recently, digital tools that help to provide rapid and predictable treatment of edentu- lous patients have become avail- able. This report describes a digital system (Digital Denture System, Wieland Dental) that allows com- plete dentures to be produced in only three appointments. A 70-year-old female patient wearing a complete maxillary den- ture had suffered an avulsion of the anterior mandibular teeth four weeks prior to her first visit. Lack of support in the posterior mandibu- lar region and continued pressure in the anterior maxillary region had led to severe atrophy. The clin- ical situation was therefore akin to the dental condition described as combination syndrome (Figs. 1a–d & 2a–b). Since the patient wanted a rapid and cost-effective rehabi- litation with removable dentures, we opted for the Digital Denture System protocol. First appointment For the preliminary impres- sion, a prefabricated impression tray was coated with a tray adhe- sive (Virtual Tray Adhesive, Ivoclar Vivadent) and the impression ma- terial was mixed with the catalyst (Virtual Putty Regular Set, Ivoclar Vivadent). After the primary im- pression had been taken, the areas where excessive compression was present were slightly reduced with the help of a micromotor hand- piece. Next, the secondary impres- sion was taken with a low-viscosity silicone (Virtual Light Body Regular Set, Ivoclar Vivadent; Fig. 3). In order to determine the preliminary maxillomandibular relation and occlusal plane, two reference points, one on the chin and one on the nose, were marked and the distance between the two points was measured. The vertical dimension of occlusion was de- termined by subtracting approxi- mately 2 to 3 mm from the soft interocclusal rest position, which corresponds to the freeway space. ACentricTray(IvoclarVivadent) was used to record the maxillo- mandibular relation. Consisting of an acrylic arch with a retention rail, this device was loaded with impression material (Virtual Putty Regular Set). We asked the patient to slowly close the jaws to the pre- liminary vertical height. After the impression material had set com- pletely, a UTS CAD device (Wieland Dental) was attached to the handle to establish the occlusal plane. This registration device measures the angle of the occlusal plane in relation to Camper’s plane (CP) and the bipupillary plane (BP). Once measured, the angles were transferred to the CAD soft- ware to reproduce the virtual posi- tion of the occlusal plane for the design of the 3-D bite plate (Digital Denture Professional add-on soft- ware module, Wieland Dental) and the denture. The Centric Tray was attached to the adapter of the UTS CAD and then the lateral braces of the bow were aligned to CP (Fig. 4). Next, the front part of the basic bow was aligned to the BP and the BP screw was fastened to secure the registration joint. The angle values of the patient were recorded on the order form, and then the form, impression and Centric Tray record were forwarded to the laboratory. In the laboratory, the impres- sions and the Centric Tray record (preliminary bite registration) were scanned using the Digital Denture Professional add-on—based on the Denture Digital Design software (3Shape)—and the ScanIt Impres- sion (3Shape) add-on. CP and BP angle modifications can be imple- mented with the latter add-on. The programme brings the two scans together and produces two virtual models of the edentulous jaws, which are aligned according to the clinical situation (Figs. 5a & b). The dental technician created a 3-D bite plate for the functional impression and the needlepoint tracing record. The models were aligned to each other on the basis of the preliminary impression. Next, the dimension of the bite rims had to be established (Fig. 6). The 3-D bite plate design allows for insertion of both the bite rim supportsforfunctionalimpression- taking and the registration plates of the Gnathometer CAD device (Wieland Dental) for needlepoint tracing. The CAD datasets of the 3-D bite plates were sent to a Zenotec select ion milling unit (Wieland Dental) for machining (Fig. 7). Second appointment Before taking of the functional impression, the bite rim supports were inserted into the 3-D bite plates. For the registration, they were simply replaced with the reg- istration plates. A polyvinyl silox- ane material (Virtual Monophase, Ivoclar Vivadent) was used for 14 Dental Tribune Asia Pacific Edition | 10/2016 TRENDS & APPLICATIONS Digital complete dentures First clinical and technical experiences with the Digital Denture System By Dr Piero Venezia and Pasquale Lacasella, Italy Figs. 2a & b: Intra-oral view: resorbed alveolar ridges and a clinical situation similar to combination syndrome.—Fig. 3: Double-mix impression of the maxilla and mandible.—Fig. 4: The UTS CAD device used to determine the occlusal plane.—Figs. 5a & b: Base for the next design steps: anatomical impression of the jaws and digitised preliminary registration.—Fig. 6: Design of the 3-D bite plate taking the needlepoint tracing appliance (Gnathometer CAD) into account.— Fig. 7: CAD/CAM-milled 3-D bite plates ready to be connected to the needlepoint tracing appliance.—Fig. 8: Functional impression with Virtual Light Body.— Fig. 9: Needlepoint tracing: centric position verified by the patient.—Fig. 10: The exactly aligned impressions (immobilised records) were digitised using a laboratory scanner.—Fig. 11: CAD tooth set-up: an extensive software library of denture teeth was used in the process. 6 7 9 10 8 11 2a 2b 4 5a 3 5b Figs. 1a–c: An edentulous patient requiring prompt and cost-effective rehabilitation of her maxilla and mandible. 1a 1b 1c 67 910