## 5 Discussion  
Total alloplastic TMJ replacement systems have become the clinical norm, rather than an exception, for management of refractory end stage TMJ disease and severe functional impairment due to pathological processes [8]. They are reported to improve the post-operative quality of life for patients, through pain alleviation, enhanced range of motion, and better speech and mastication [25]. Irrespective of whether it is a stock or a custom-made prosthesis, alloplastic TMJ replacements have been shown to deliver predictable clinical outcomes in terms of TMJ function [26]. However, custom-made joint replacements were considered suitable only for specific indications such as in TMJ with severe degenerative anatomic changes, failure of stock prosthesis, and concomitant correction of skeletal and dental malocclusion [26]. Interestingly, almost all commercially available custom-made TMJ prosthesis systems, utilize stock condple and glenoid fossa components designed over a custom fitted fixation plate or implant [15; 26; 27]. This makes them at best custom-fitted TMJ implants in contrast to the custom fabricated TMJ, condple and glenoid fossa parts which the present study envisioned. The idea of total alloplastic TMJ reconstruction is definitely motivated from the clinical success of similar procedures in orthopedic surgery for more than half a century [8; 25; 26]. As a result of which, the concept of ball (condple) and socket (glenoid fossa) articulating components have been largely favored in both stock and custom-fitted alloplastic TMJs [8; 21]. In addition, eliminating translational joint movement, the ball and socket TMJ design is routinely fabricated with a short condylar component and thick glenoid fossa component, in order to match with the low center of rotation of the natural joint [21; 28]. While this may sound practical in clinical scenarios involving bilateral TMJ replacement, unilateral TMJ replacement with currently available alloplastic joint prostheses, could reportedly increase stresses at the condple and disc articulating surfaces [29]. Based on the above premise, it could be surmised that the custom fabricated alloplastic TMJ design, based on 3D modelling and mirroring of anatomic condple and glenoid fossa, would simulate clinical rotational and translational joint movements. Therefore, the biomechanical simulation assessment was also designed to that effect. The three biomaterials evaluated in the present study are not new to the fields of medicine and dentistry, and are being routinely used clinically. Titanium and its alloy (Ti6 Al4V) are among the most biocompatible materials used in the fabrication of end osseous orthopedic and dental implants [20; 30]. The unique aspect of the titanium alloy used in the present study was only the additive method (EBM) used in its fabrication. Nevertheless, implants of titanium alloys made using advanced manufacturing methodologies such as EBM are equally biocompatible and possess regulatory healthcare approvals [14; 19; 20]. Based on a clinical case report, [PERSON] et al. [23] have reported successful esthetic and functional reconstruction of the entire mandible printed out of titanium alloy (Ti6 Al4V-ELI) using EBM technology. Interestingly, the same titanium alloy and fabrication protocol have been utilized in the present study too. Zirconia or zirconium dioxide is a biocompatible ceramic material used successfully in dentistry for restorative treatment, due to its favorable biomechanical properties and low affinity to dental plaque. In the past decade it has gained popularity as an alternative to titanium for the fabrication of end osseous dental implants, owing to its biocompatibility and the ability to osseointegrate similar to titanium [31; 32]. Similarly, poly (methyl methacrylate) (PMMA/acrylic), a low weight polymer with good tensile strength and high modulus of elasticity, is used in clinical dentistry as a denture base material.