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Chapter 240Walter Lorenz Surgical Inc. (now Biomet Microfixation, Jacksonville, FL, USA) also released a stock prosthesis. The glenoid fossa was made from UHMWPE (ArCom) and was provided in three different sizes ranging from small to large.(12,18) Although initially additional fixation of the fossa could be obtained using PMMA cement, this approach was abandoned due to the risk of thermal damage. Furthermore, fragmentation of PMMA under functional loading was observed.(18) The mandibular component consisted of a CoCr alloy and the ramal surface of the condylar implant was coated with titanium plasma spray, creating a rougher surface. Like the fossa, the ramal component was provided in three different lengths (45, 50, and 55 mm) and styles (standard, narrow, and offset).(12) All components were freely interchangeable and selection was made based on the patient’s anatomy. The system received FDA approval ten years after its initial release in 1995 and has been used widely since then. A recently released 3-year follow-up by Giannakopoulos et al.(12) (OCEBM LOE IV), with over 442 implants, revealed satisfactory results. A significant decrease in pain intensity was found, while a significant improvement in mouth opening and jaw function were seen. Furthermore, no device-related mechanical failures were observed. A follow-up study by Lobo Leandro et al.(45) (OCEBM LOE IV), which included 300 patients, reported similar results. In 1996, due to reports of fragmentation of PMMA under functional loading, Chase reinvented Christensen’s prosthesis, now known as the Nexus CMF system, by replacing the PMMA condylar head with a CoCr condylar head.(7,11) This change was inspired by metal-on-metal systems that were used in orthopedic hip prostheses, although Chase and Christensen both failed to recognize the difference in loading between both the hip joint and the TMJ, which would have dire consequences for the system.(7) Two years later, Christensen developed a metal-on-metal all cast CoCr TJR system, which was designed and manufactured much like the TMJ Concepts system.(18) Initial short-term clinical studies were positive, boasting lower amounts of wear compared to metal-on-acrylic systems, as well as good clinical results. This led to FDA approval for the device in 2001.(46,47) However, longterm studies reported on patients with metallosis, prosthesis loosening, osteolysis, and implant failure. As a result, the approval was withdrawn in 2015 and production of the device has halted.(7) Nikolas de Meurechy NW.indd 40 05-06-2024 10:14