Page 67 - Demo

Biomaterials in TMJ replacement653the outer layers consisted of a mixture of Teflon and carbon fibers, known as Proplast. While initially highly popular, it became apparent several years after the first placement, that the disc was not suited for in vivo functional loading, resulting in excessive wear, leading to debris accumulation in the fossa region, triggering a foreign body giant cell reaction and eventual bone resorption. As a result, production was halted in 1990 and in 1991 the USA Food and Drug Administration (FDA) recommended the removal of all Proplast/Teflon devices.(6,7,12,23,24) The Silastic disc underwent a similar fate, as functional loading led to fragmentation of the silicone elastomer, with abandonment of the disc prosthesis in 1993.(6,25) Condylar prosthesesPolymer materials also came into use for condylar prostheses. The first polymer prosthesis was released in 1964 by Hahn et al.(26) , which consisted of an acrylic (polymethymethacrylate (PMMA)) caput and Vitallium mesh condylus. Shortly thereafter, several more prostheses followed, such as the vitreous carbon coated CoCr condylar prosthesis by Kent in 1972 and the titanium prosthesis by Raveh.(6,12) In 1992, however, Lindqvist et al.(27) concluded that use of a condylar replacement alone led to resorption of the fossa, indicating that using solely a condylar replacement is insufficient as treatment. Westermark et al.(28) also came to the same conclusion and advocated the use of a total TMJ prosthesis instead of replacing only the condyle.Total temporomandibular joint prostheses The total TMJ prosthesis was first reported in 1970 by Christensen et al.(12,29), who combined their previously developed CoCr fossaeminence prosthesis with a new CoCr condylar prosthesis incorporating a PMMA condylar head.(21,22) Because of particulation of the PMMA, it was later replaced by CoCr.(7,30) Further development of the total TMJ prosthesis introduced several new designs using a wide variety of materials, such as the metal-only CoCr prosthesis by Kummoona(31) or the titanium-palladium (TiPd) alloy condyle and PE fossa prosthesis by Sonnenburg and Sonnenburg.(32) However, of the many total TMJ implant designs, the Vitek-Kent total joint prosthesis (Fig. 2) was the first system to be used extensively in the United States of America (USA), resulting Nikolas de Meurechy NW.indd 65 05-06-2024 10:14