The Christiansen total TM joint prothesis fossa element is composed of cobalt-chromium alloy. Both precured polymethylmethacrylate and cobalt-chromium condylar elements have been used with this system however the “universal” condylar prosthesis is composed of a polymethylmethacrylate head and cobaltchromium ramus element. Though a patient-specific prosthesis can be fabricated using CAD-CAM technology, stock elements are available. The Lorenz total TM joint prosthesis is composed of cobalt-chromium ramus component. The host-bone surface of the ramus component is roughened with a titanium plasma coating. The fossa element is made of ultra-high molecular weight polyethylene that is stabilized with screws. Polymethylmethacrylate bone  cement may also be used to fill voids but the cement is not designed as a load bearing medium.