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Machinability of IPS empress 2 framework ceramic. Potential for ceramic dentures

: Schmidt, C.; Weigl, P.


Journal of biomedical materials research 53 (2000), No.4, pp.348-352
ISSN: 0021-9304
Journal Article
Fraunhofer IPT ()
IPS empress 2 framework ceramic; dental ceramic; machining; grinding; ductile behavior

Using ceramic materials for an automatic production of ceramic dentures by CAD/CAM is a challenge, because a lot of technological, medical and optical demands have to be considered. The IPS Empress 2 framework ceramic keeps most of it. This study shows possibilities to machine this ceramic with economical parameters. A long life time behavior of ceramic denture requires a ductile machined surface to avoid the well- known subsurface damages of brittle materials caused by machining. Slow and rapid damage propagation begins at break outs and cracks and limits life time significantly. Therefore ductile machined surfaces are an important demand to machine dental ceramics. The machining tests were performed with various parameters such as tool grain size and feed speed. Denture Ceramics were machined by jig grinding on a 5 axis CNC milling machine Maho HGF 500 with a high speed spindle up to 120.000 rpm. Result of the wear test was low tool wear. With one tool you are able to machine eight occlusal surfaces by roughing and finishing. One occlusal surface takes about 60 minutes machining time. Recommended parameters for roughing are middle diamond grain size (D 107), cutting speed v(c) = 4.7 m/s, feed speed v(ft) = 1000 mm/min, depth of cut a(e) = 0.06 mm, with of contact a(p) = 0.8 and for finishing ultra fine diamond grain size (D46), cutting speed v(c) = 4.7 m/s, feed speed v(ft) = 100 mm/min, depth of cut a(e) = 0.02 mm, width of contact a(p) = 0.8. The results of the machining tests give a reference for using IPS Empress 2 framework ceramic in CAD/CAM-Systems.