Page 39 - Demo

Historical evolution of the TMJ prosthesis372the ‘fibrous cushion’ would reduce wear and tear. Kummoona tested this prosthesis in primates and found that 50% failed after 9-10 months due to dislocation of the condylar component. (35) Post-euthanasia dissection together with microscopic and microradiographic examinations showed that the prosthesis had acceptable biological tolerance.In 1983, the Vitek-Kent prosthesis was created.(12,20,36) This prosthesis has arguably shaped the history and evolution of the TMJ prosthesis more than any other design, albeit not in a positive way. As stated earlier, Kent noticed that the use of only a condylar prosthesis led to resorption of the fossa. In response to this problem, the condylar component was redesigned to have a more flattened and elongated head, and a fossa component was developed. Originally, the fossa component had a bilaminated structure. The articulating side consisted of a 2-mm high density PTFE coating (Teflon). The surface of the tissue-side consisted of a more porous carbon fibre-reinforced Teflon, also known as Proplast I. Later, this layer was altered to an aluminum oxide fiber-reinforced Teflon layer (Proplast II). Also the medial aspect of the ramus was coated with Proplast. The shape of the fossa prosthesis was pre-operatively based on lateral radiographic tracing and could be adapted further by carving, after which it was fixed to the zygomatic arch using three screws.(12,19,20) However, it quickly became apparent that Teflon was not suitable as an articulating surface, as wear debris began accumulating only several years after implantation of both the implant system and the Teflon interpositional disc replacement. This led to foreign body giant cell reactions (FBGCR), bone resorption, and refractory pain syndromes. In response to these complaints the articulating Teflon layer of the fossa component was replaced with an ultra-high molecular weight polyethylene (UHMWPE) layer in 1986.(12,18,19,36) Despite this attempt to salvage both the TJR system and the disc prosthesis, Proplast then proved insufficiently strong, resulting in fragmentation of the material.As both the Vitek disc implant and the Vitek-Kent system gained considerable popularity among maxillo-facial surgeons, leading to their implantation in several thousand patients, the backlash was equally Nikolas de Meurechy NW.indd 37 05-06-2024 10:14