## 1 Introduction  
Total temporomandibular joint (TMJ) replacement and reconstruction have become the treatment of choice for irreversibly damaged joints as a result of inflammatory and degenerative processes. In addition TMJ replacement provides a plausible functional treatment choice in the treatment of TMJ ankylosis [1]. Although several materials, both autologous and alloplastic have been reportedly used for TMJ replacement and reconstruction, the goals of achieving a stable joint which supports oral function and facial form remain the same [2]. The TMJ is a unique synovial joint in the body, which includes bilateral synchronous articulation between two bones, the mandibular condyles, and the glenoid fossae of the temporal bones [3]. In addition to the anatomic features of synovial joints, such as fibrous tissue capsule with synovial lining and fluid, fibrocartilaginous disc, and support ligaments, the TMJ is also characterized by rotational and translational movements during function (ginglymoarthvial joint) [4]. Although the left and right TMJ are two separate synovial joints, together they physiologically comprise the craniomalibular articulation [4]. Due to the above-mentioned anatomic, functional, and physiological complexities, the choice of TMJ reconstruction or replacement has to be decided based on the clinical condition, pre-existing pathology, and patient needs [2]. While several studies have reported the use of autogenous bone and soft tissue for functional reconstruction of the TMJ [2; 5; 6], total alloplastic replacement has emerged as the preferred treatment for management of refractory joint disease, including failed autologous joint reconstruction [7; 8; 9]. The only contraindications for alloplastic TMJ replacement could be chronic focus of infection at the surgical site and documented hypersensitivity to the material used [8]. Originally conceptualized based on prosthetic hip joints, alloplastic TMJ have come a long way and have been used with considerable clinical success for more than three decades and several systems of prosthetic joints are commercially available [8; 10; 11]. The predominantly used combinations of alloplastic biomaterials for fabrication of prosthetic TMJ include titanium or cobalt-chrome (Co-Cr) alloy for the condyle and titanium, ultra-high molecular weight poly-ethylene (UHMWPE), or Co-Cr alloy for the glenoid fossa [8; 12]. Although biocompatible, most currently available prosthetic TMJ systems avoid metal-on-metal articulations owing to the risk of foreign body giant-cell reactions to metallic particles generated at the contact points [13]. Furthermore, majority of these systems involved the use of a custom-fitted stock prosthetic TMJ, which requires sufficient intra-operative time for fixation [14]. While the idea of custom-made TMJ prostheses are not new, they have gained greater importance owing to advances in craniofacial radiology and patient specific digital design modalities [10; 15; 16]. Custom fabrication enables better adaptability of the surgical prostheses, reduces surgical time, and restores form and function with greater predictability [16]. Consequently, newer trends in patient specific total alloplastic TMJ replacements has fueled the need for newer biomaterials which are capable of custom fabrication. Several additive manufacturing technologies such as selective laser melting (SLM) [17], direct metal laser sintering (DMLS) [18], and electron beam melting (EBM) [19], have been employed for custom fabrication of biomedical implants. EBM is approved by the United States Food and Drug Administration (USFDA) for the fabrication of orthopedic and cranio-maxillofacial implants using an alloy of titanium (Ti6 Al4V) [20]. In comparison to stock implants milled out of solid titanium, EBM enables precise fabrication of patient specific implants based on three-dimensional (3D) radiographic images of the patients [19].