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CAD0111

Fig. 1_Pre-op situation: The buccal wall of tooth #25 is cracked and features a large damaged composite filling, a clear indication for a crown. Fig. 2_A digital impression is taken of the preparation, as well as the antagonists and the situation in centric occlusion (CEREC Bluecam, Sirona) from the buccal aspect (middle). Fig. 3_Semi-automatic alignment of the upper and lower jaw models with the help of the buccal image. Fig. 4_The biogeneric crown software designs an occlusal surface according to the individual situation. Fig. 5_Bucco-oral cross-section of the restoration. The minimum occlusal thickness of 1.5 mm is checked. 38 I I industry report _ IPS e.max CAD LT _CAD/CAM technology allows dental profes- sionals to manufacture solid all-ceramic crowns chairside. A digital image of the preparation is capturedwithanintra-oralcameraandthecrownis designed accordingly. A variety of ceramics are available for the construction of the crown, for exampleanaesthetic,easy-to-millceramic(IPSEm- press CAD, Ivoclar Vivadent). As this leucite glass- ceramic is weaker than zirconium oxide, these crowns must be seated using the adhesive tech- nique (for example with Syntac/Variolink II or Mul- tilink Automix). This makes them strong enough to withstand the masticatory forces in the long term. IPS e.max CAD, which has been on the market forsometime,isalithium-disilicateglass-ceramic (LS2) that demonstrates a flexural strength of 360 MPa. This ceramic is machined to the desired shape while it is still in its metasilicate or ‘blue’ state (approximately 130 MPa). Subsequently, the ceramic is crystallised for 20 minutes. During this process, the material attains its final state and develops its excellent mechanical and aesthetic properties. IPSe.maxCADisavailableinalow-translucency (LT) version, which is suitable for the fabrication of crowns and implant-retained crowns. The high-translucency form is intended for the con- struction of inlays and partial crowns. The stains and glaze are applied before the crystallisation process. As a result, subsequent polishing is un- necessary. Owing to the high strength of the restoration, adhesive cementation with a sepa- rate dentine conditioner is not indicated as long as the thickness of the ceramic does not fall be- low 1.5 mm. Self-adhesive cementation materials can be used. The new self-adhesive composite cement SpeedCEM is particularly suitable for this purpose. Thechairsidecreationofacrownisdescribedon the basis of a clinical case using IPS e.max CAD LT and the new SpeedCEM luting cement. CAD/CAM 1_2011 Computer-aided crown design Author_ Dr Andreas Bindl, Switzerland Fig. 1 Fig. 4 Fig. 5 Fig. 2 Fig. 3