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Animal experiment: Inflammatory cell response evaluation1636IntroductionSince total temporomandibular joint replacement (TMJR) was first introduced in modern medicine, many different systems have been developed.(1,2) Whilst the indications for the prosthetic replacement have become well-defined (3,4), the quality standards these systems need to meet, remain poorly regulated. Often proper in vivo and in vitro testing of TMJR prostheses is lacking, (5) with implantation of unsuited materials potentially leading to significant, detrimental, patient side effects such as synovitis, foreign body giant cell reactions (FBGCR), bone resorption and implant failure. (1,6–9) One such example is the Vitek-Kent. Although the system seemed promising at first, the 2mm thick articulating Teflon coating was found to be an unsuitable articulating surface. This resulted in the accumulation of wear debris several years after implantation, leading to severe local reactions and finally a recommendation of removal by both the US Food and Drug Administration (FDA) and the American Association of Oral and Maxillofacial Surgeons.(1,8,9) This illustrates the absolute importance of proper TJR evaluation, before human application. Thus, in order to properly evaluate a novel patientspecific additively titanium (Ti) alloy TMJ replacement system developed by CADskills BV (Ghent, Belgium), an in vivo animal experiment, using a sheep model, was designed. Three focal points were selected for investigation: Wear, lateral pterygoid muscle (LPM) enthesis integration and adverse tissue reactions.(5,10) Previously published papers evaluated and discussed the development of the TMJR, implant integration, LPM enthesis reconstruction, wear rates of both the fossa and condylar components.(5,10,11) This paper aims to evaluate the amount of inflammation of the peri-articular tissues, whilst also comparing the inflammatory response in TMJR with and without a condylar diamond-like carbon (DLC) coating.(6) For more information concerning this coating and its effect on wear, we refer to two of our previous papers that discuss this at length, as this is beyond the scope of this paper.(5,11)Nikolas de Meurechy NW.indd 163 05-06-2024 10:14