CDEN0110

I 45 meetings _ 9th Ceramics Symposium I cosmeticdentistry 1_2010 (ZrO2) have an opaque structure and require ve- neering. Owing to its partial translucency, Al2O3 is especiallysuitableforcrownandFDPframeworks in the anterior and premolar regions. ZrO2 is indi- cated for use not only in the posterior dentition, but also as a framework with wings for adhesive FDPs. Prof Reich discussed the veneering frac- turesonZrO2 frameworks,whichhavebeenunder discussion in the professional community for sometime.Theunderlyingproblemisthatupuntil a few years ago, thin-walled crown copings were covered with thick veneer layers, and the bridges lacked anatomically designed frameworks with cusp support. _Substance conservation as the goal Prof Karl-Heinz Kunzelmann (Ludwig Maxi- milian University of Munich, Germany) lectured on Ceramic inlays and partial crowns: New preparation concepts, pointing out that current preparation criteria are still heavily influenced by—the limitations of early ceramic materials and CAD/CAM systems. Today, given the good fitting accuracy of ceramic restorations, the enlarged divergence angles of the gold era are no longer necessary (Figs. 1a–f). Thus, classical divergence angles of 6 to 10° are to be avoided, owing to the risk of the cavity margin ending in the area of the cusp tips or contact points. Occlusal surface ve- neers of pressable ceramic, suitable for the treat- ment of occlusal defects and vertically increasing occlusion, do not require a chamfer and con- serve considerable substance. In partial crowns with cusp reconstruction, a substance-conserv- ing supporting area in the enamel-dentine region is preferable to a supporting shoulder. An overlay isindicatedwhencuspsareverythin(<2mmcusp thickness). According to Prof Kunzelmann, the reimbursement for overlaying cusps should be adjusted because the statutory health insurance criteria for the partial-crown indication require that all cusps be sacrificed. However, this contra- dicts the principle of substance conservation. Dr Andreas Kurbad (Germany) covered the range from Classical crown to minimally invasive. In the preparation of a fully anatomical ceram- ic crown with a circular chamfer, up to 64 % of the hard dental tissue can be conserved.1 In contrast, metal-supported full crowns consume atleast70%inpreparingthenecessaryretention surfaces.2 A sure positioning of the crown is facilitated byclearmargins.Itshouldbetactilelyperceptible when the ceramic body has reached its correct position. Further, the advantage of adhesive Fig. 2_Fracture of a veneered ZrO2 bridge. The framework was ground in palatinally (pointed droplet shape) and did not support the veneer adequately. The over-dimensioned veneering layer became subject to tensile forces. (Photograph courtesy of Prof Ulrich Lohbauer, Germany) Fig. 3_Cusp-supporting coping form prevents veneering fractures. (Photograph courtesy of Prof Joachim Tinschert, Germany) Fig. 4_Embedding the CAD/CAM-milled wax-up in order to obtain a pressed veneer. (Photograph courtesy of Volker Brosch, Germany) Fig. 5_Pressed veneers (IPS e.max Press) with final firing on ZrO2 framework. (Photograph courtesy of Volker Brosch, Germany) Fig. 2 Fig. 3 Fig. 4 Fig. 5