THE JOURNAL OF THE TOKYO DENTAL COLLEGE SOCIETY

Vol. 109 No. 1      February 2009

ISSN: 0037-3710      UBIC: 342-J

ABSTRACT

The number of clinical cases in which zirconia copings are used for implant superstructures has recently increased. The progress of CAD/CAM technology has enabled the milling of lot only single crowns and 3-unit-bridges, but also long-span bridges. However, since the number of implants and pontics increases in these long-span bridge cases, there is the possibility that the poor fitting of superstructures will occur. Therefore, in this study, we produced one-piece bridges using zirconia for full mouth reconstruction, and evaluated their fit. A master model was produced by fixing the labo-analogue of 7 Straumann implants. This master model was laser-scanned into the CAD/CAM (ZENO Tec system, WIELAND). A one-piece bridge with 7 implant copings and 7 pontics was designed on a computer. Eight one-piece bridges were cut from 8 zirconia blocks. To measure the marginal discrepancy in each implant, after injecting a vinyl polysiloxane impression material onto the internal surface of the copings, the bridge was set in the metal model, and load of 4.9N was evenly applied to the framework. The thickness of the impression material in the margin area on the medial, distal, buccal, and lingual sides of each implant was measured using a stereoscope. Marginal discrepancy in each implant ranged from 9µ.tm to 121µm. No significant differences were noted among implants, however. These results showed that the fitting accuracy of zirconia copings of long-span bridges ranged widely. Therefore, some technical measures to reduce this discrepancy should be considered in clinical practice. (The Shikwa Gakuho, 109 : 44-49, 2009) Key words: CAD/CAM, Zirconia, Implant, Fitting accuracy, ZENO Tec system

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