Wear-testing of a temporomandibular joint prosthesis: UHMWPE and PTFE against a metal ball, in water and in serum

For a temporomandibular joint prosthesis, an estimation of the wear rate wa s needed, prior to patient application. Therefore, we determined the in vit ro wear rate of the ball-socket articulation of this prosthesis, consisting of a metal head and an ultra-high molecular weight polyethylene (UHMWPE) c up. The basic testing configuration consisted of one 8-mm diameter stainles s-steel ball, rotating between two conforming cups with a minimum thickness of 5 mm. For validation of the testing apparatus, two cup materials, in tw o lubricants, were tested. Both cup materials, UHMWPE and polytetrafluoroet hylene (PTFE) were tested in deionized water, as well as in a serum-based s olution. For UHMWPE in serum, eight samples were tested, for the other comb inations four samples. For UHMWPE, the tests ran for 7 million cycles, for PTFE between 0.8 and 1.7 million cycles. For UHMWPE, the wear rate was 0.00 6 and 0.47 (mm(3)/10(6) cycles), in water and in serum, respectively. For P TFE, the wear rate was 2.8 and 47 (mm(3)/10(6) cycles), in water and in ser um, respectively. For reason that testing in serum simulates the in vivo si tuation best, it was concluded that the wear rate of the TMJ prosthesis art iculation is 0.47 (mm(3)/10(6) cycles), which is considered acceptable. (C) 1999 Elsevier Science Ltd. All rights reserved.