## 1 Introduction  
Computer-aided design and computer-aided manufacturing (CAD-CAM) have been gaining popularity in restorative dentistry [1]. Among the main reasons are the ongoing technological development of CAD software programs, 3D printing and milling procedures. In this context, the process of producing CAD-CAM restorations is sensitive to every step of the methodology, regardless of the material to be used in the manufacturing process. Interim CAD-CAM restorations can be designed on intraoral scans (IOS) of tooth preparations imported into CAD software and produced with milled PMMA with satisfactory accuracy to manage surrounding soft tissues and predict esthetic and functional outcomesof permanent crowns [2; 3]. Interim crowns can also be produced with light-cured resin by means of 3D printing. This, in turn, is an additive manufacturing method to manufacture solid objects layer-by-layer from a 3D digital design file, usually offered in the \"Standard Tessellation Language\" (STL) extension [4; 5]. This digital workflow is achieved with enhanced communication between patients and professionals, as well as among different professionals (i.e., dentists, dental technologists, etc.) [2]. As a result, metal-free esthetic restorations have obtained an increasing space in the market. The number of biomaterials used in dental CAD-CAM has also increased, along with blocks and discs (blanks) of feldspar ceramics, titanium, zirconia, lithium disilicate, cobalt chromium and resin for temporary prostheses, depending on the purpose of the treatment. It is suggested that all the steps of a digital workflow (i.e., intraoral scan, CAD and CAM) may influence the fitting precision of indirect permanent restorations [1; 2]. Dental commercial CAD software programs usually have similar tools and workflow interfaces. First, the professional should start by inputting the patient's data, as well as details of the project to be performed. This is carried out along with the identification of the dentist, technician and type of work performed, which are stored in the patient's file and used with the next software program of the workflow, which will be used to digitally design the restorations registered in the project. Such software interface also enables the possibility of importing and using the patient's photographs, which in turn can be integrated and superimposed with intraoral scans of the patient, and even cone-beam-computed tomographic scans, if surgical procedures involving bone tissue are also part of the project [1; 2; 6]. One very important difference between software programs, however, is the number and types of tooth libraries available. It is important to choose a tooth library compatible with the patient's face and dental arch [7; 8; 9]. For this reason, a satisfactory protocol of clinical photographs should always be used in the initial appointments of the patient. To address this difference and decrease the level of bias, previous research studies have used mirroring techniques to compare CAD software programs, instead of using standardized libraries [3; 9]. There are two main types of digital workflow in restorative dentistry: laboratory and chairside workflows. In this context, chairside CAD-CAM systems usually have intraoral scanners integrated with milling devices of the same brand. On the other hand, open CAD software programs have also developed chairside versions, with interfaces that are user-friendly for dental clinicians [1]. It is unclear, however, what is the impact of the choice of CAD-CAM system and related materials on the final CAD-CAM restoration. Recent previous studies have found that CAD-CAM outperforms conventional prostheses regarding clinical outcomes [3]. On the other hand, CAD-CAM requires digitally waxing tooth morphology by copying/mirroring a contralateral tooth or using CAD software libraries, followed by personalized adjustments [1]. These, in turn, are time-consuming and may influence the adaptation [7], as well as functional and esthetic features of the final restoration [1].