A comparative outcome evaluation of digitally and conventionally fabricated maxillofacial prosthesis: A cross -over randomized control trial.

Dimensional accuracy of the final prosthesis made by conventional or digital technique will be assessed in terms of marginal fit, weight of the prosthesis, retention/ stability. For this anatomic landmarks on the normal side of the  patient will be identified according to the standardized definitions e.g  glabella, chin, ear, Endocanthion [En], exocanthion [Ex],palpebral superiors [Ps], and palpebral inferiors [pi] which may be used as reference depending upon the location of defect (eye/ ear/ nose).

For this two facial scan will be done one without the prosthesis and another with the prosthesis using the anatomic landmarks as reference, the two scans will be superimposed to evaluate the marginal fit. The weight and retention and stability of the prosthesis will be assessed clinically.

Maxillofacial prostheses restore oral function, including mastication, and improve esthetics and well-being.  The size of the lesion has an inversely proportional impact on the retention, stability, and consistency of the prosthesis, with larger prostheses being heavier and having less retention. Silicone is typically used to fabricate maxillofacial prostheses and offers the advantages of lightness, favorable physicochemical properties, and biocompatibility. Despite its common use, silicone prostheses require frequent replacement because of the discoloration and degradation caused by environmental factors such as temperature variations and ultraviolet radiation. Maxillofacial prostheses have typically been manufactured using a conventional process of pouring silicone into molds. However, the development of computer-aided design and computer-aided manufacturing (CAD-CAM) systems for maxillofacial rehabilitation has resulted in a radical change in the prosthesis fabrication process. Digital technology allows for the virtual planning, design, and manufacture of prostheses.  Scanners are used to capture accurate digital scans with low data redundancy, high speed, precision, and safety. Moreover, they can overcome the limitations of the conventional impression technique, such as patient discomfort and soft tissue distortion, at an increased speed. The digital workflow starts by scanning the patient’s face to obtain anatomic data. A design software program then processes the scan and produces a 3- dimensional (3D) cast of the prosthesis that is later manufactured. Digital databases have recently been proposed to facilitate the generation of anatomic parts during the design process. Some 3D printers have been developed to allow direct fabrication of silicone prostheses from 3D casts in an additive manufacturing process in which parts are built layer-by-layer. Single droplets of silicone are dosed onto the working surface according to the standard tessellation language (STL) mesh and then polymerized in layers with ultraviolet light. Hence, printable silicone must flow at a constant rate, retain its shape, and have a controllable polymerization rate.The 3D printing of silicones is the last step of a more accurate, more rapid, and less expensive digital approach to fabricate maxillofacial prostheses.