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ePaper created 2018-02-16, 11:17:41 | version 1.38.0
| case report restoration of the edentulous maxilla Screw-retained implant-supported restoration in the edentulous maxilla A working document for the production of a milled zirconium dioxide framework Authors: Dr Octavian Fagaras & Milos Miladinov, Romania When veneering zirconium dioxide frameworks, manual dexterity and a profound knowledge of the materials is required. The correct use of the materials is decisive for success. A screw-retained and there- fore conditionally removable restoration is a proven concept for the implant prosthetic treatment of an edentulous maxilla. Zirconium dioxide is a frame- work material that can support a long-lasting result. A state-of-the-art zirconium dioxide material such as Zenostar T (Wieland Dental) and innovative ce- ramic veneering systems (such as IPS e.max Ceram, Ivoclar Vivadent) enable natural-looking prosthetic restorations to be achieved in an efficient manner. In principle, zirconium dioxide is a sophisticated mate- rial that requires correct and skilled application. Introduction to a patient case An implant-supported, screw- retained bridge was planned for the edentulous maxilla. Based on defined backward planning, six implants were inserted into the patient’s jaw. After the healing phase, the im- plants in the visible region were provided with trans- versal screw-retained abutments. In the molar region, the final bridge restoration would be occlusally screw-retained. Important parameter for framework production A set-up of the planned restoration was used as a basis for the CAD/CAM-supported production (Zenotec, Wieland Dental) of the zirconium dioxide framework. After digitisation in the design soft- ware, the framework shape was reduced according to the cut-back technique. This method created suf- ficient space for the veneer. The digital structure was first milled in wax so that the fit and precision could be checked (Fig. 1). Subsequently, the framework was milled from a Zenostar T disc. During framework construction, it was necessary to include sintering drops as an occlusal support for the restoration so that distortion would be prevented during sintering in the Zenotec sintering furnace. In doing so, the restoration was not to be separated from the occlu- sal tongue (Fig. 2). Sintering distortion was avoided with this method. The sintering process was carried out in the compact, high-temperature Zenotec Fire P1 sintering furnace, which is supplied with pre-in- stalled programmes. This sintering furnace can also be freely programmed so that other sintering pro- grammes can be used. We selected the “long pro- gramme”. The heating-up and cooling-down phases Fig. 1: The structure milled in wax to check the fit. Fig. 2: The framework was fabricated using zirconium dioxide (Zenostar). Fig. 1 Fig. 2 20 CAD/CAM 4 2017