52 4. The outer surface of the coping to which the porcelain or the resin material will be attached later is milled. 5. To allow the removal of the coping from the block, the connecting part between the coping and the remaining block is cut. 6. The time required for milling a single crown coping is about 30 to 45 minutes. About 90 to 120 minutes are required for the 3 unit FPD coping. 7. The infrastructure for ceramic crown can also be milled using this system form a block of high performance METROXIT ZIRCONIUM OXIDE TZP BIOCERAMICR type TAP (tetragonal polycrystalline Zirconium oxide). FINISHING AND POLISHING: Finishing and polishing are performed in the conventional manner on the die. Porcelain or composite resin can be used as a facing material and is applied with the conventional method.
ACCURACY AT THE MARGINS: The average gap between the coping and die at the margin is 30 to 50 micrometer. Although there is stillroom for improvement, it is fair to conclude that this system is able to achieve clinically acceptable marginal accuracy comparable to that of conventional complete cast crown (30 to 50 microns) and other CAD/CAM system (50 to 100 microns). PROCERA SYSTEM This process for manufacturing crowns, process and implant superstructures uses a combination of copy milling, spark erosion and laser welding. PROCERA technology was first developed for processing titanium. The application of PROCERA system for manufacturing individual crown made of extremely dense sintered aluminium oxide ceramics resulted with the increasing demand for improved aesthetics. ALUMINIUM OXIDE CERAICS: Crowns manufactured with PROCERA system shows strength values never reached by an all-ceramic system. Flexural strength is 699 +/-70.8 Mpa according to the manufacture. ANDERSSON and ODEN research at the UNIVERSITY of MICHIGEN indicates a flexural strength approximately twice as high as that of INCERAM and more than three times of other ALL-CERAM systems. THE PROCERA ALL-CERAMIC SYSTEM: The three main parts of the PROCERA system are: 1. A scanner, 2. A personal computer, 3. A modern or disk for transmission of data to the workstation.