## 4 Discussion  
Due to the early detection of malignant pathology and greater surgical predictability for solving cancer lesions, the demand for maxillofacial prostheses, as defined by The Glossary of Prostodontic Terms, Ninth Edition [76], is \"any prosthesis used to replace part or all of any stomatognathic and/or craniofacial structures\", and it has dramatically increased.  
A digital workflow became used more and more in maxillofacial prosthodonics in recent years. However, compared with the great progress and popularity registered by the CAD and CAM technology in other dental specialties, such as fixed and removable prosthodonics, aesthetics, dental implantology and orthodontics, its development in maxillofacial prosthetics was, to date, limited and slow [77].  
Among the first published cases on digital technologies in maxillofacial prosthodonics, [PERSON] et al. [71] described in 1999 a technique for obtaining an individual, life-sized, three-dimensional ear model using the CT scan of the patient and a workstation, Endoplan (Medical Diagnostic Computing, Zeiss, Germany), with a semiautomatic contouring program for CBCT segmentation of the soft tissue, based on Hounsfield units (HU) thresholding.  
Several technical notes, case reports and even case studies have been published since then, but the existing literature is scarce in presenting a reliable protocol for the use of CAD and CAM technology in the rehabilitation of patients with maxill facial defects. Digital obturator developments occurred only in recent years by [PERSON] et al. (2016) [3], [PERSON] et al. (2017) [44], [PERSON] and [PERSON] (2017) [43] and [PERSON] et al. (2017) [42], but with promising results.  
Adopting digital workflows is often challenging and sometimes prone to errors, which need to be identified and reported so the mistakes are not repeated [78; 79]. The sample size of participants in the published papers on CAD and CAM in maxillofacial prosthodonics is low.  
From the reviewed literature on digital workflows in maxillofacial prosthodonics, most of the papers published so far were case reports (with one to three participants), case series or proofs of concept (Table 1). In the majority of the papers, no direct comparison of patient outcomes to the conventional treatment method was provided. One exception is the paper published by [PERSON] et al., who compared the prostheses fabricated by 3D printing for a patient with rhinectomy (total nose removal) to a prosthesis made by conventional techniques [59]. For the computer-aided workflow, an indirect approach produced a mold via AM. The final prosthesis was judged by experts to be clinically acceptable and was rated as superior to the conventional one [59]. [PERSON] and [PERSON] simulated the surrounding tissue movements in the design of auricular prostheses and compared them to a conventionally manufactured ear epithesis in a case series of five participants [16]. The digitally designed and conventionally designed prostheses were assessed by both the clinician and the participant for the acceptability of its fit, shape and retention and, based on the findings, a workflow for manipulating scan data was developed [16].  
In addition, the great number of trauma cases in the maxillofacial region, with frequent permanent deficits and potential disfigurents [80], made several research groups determined to develop digital workflows, which include computer-assisted surgical planningand intraoperative navigation for increasing the predictability of defect restoration and improving a patient's quality of life [81].  
We aimed in the present review to analyze the available published data, taking into consideration the key elements of the digital workflow for maxillofacial prosthesis production: data collection, editing (visualization), design, manufacturing and evaluation (assessment of accuracy), with a deeper focus on the first three aspects.