## 4 Discussion  
This preliminary in vivo study aimed to compare patient satisfaction and clinical outcomes of anterior rehabilitation with multiple CAD-CAM milled single crowns designed by professionals with different backgrounds and levels of expertise. According to the present findings, CAD-CAM anterior interim rehabilitation had increased patient satisfaction, compared to the initial conventional temporary rehabilitation, which is supported by previous studies [1]. Furthermore, the superior results found herein by the group CAD over group DENT support the importance of the learning curve in dental digital workflow [2]. In this context, digital waxing performed after integration and alignment of IOS and patient pictures or facial scans require software knowledge and practice [3]. This study supports the importance of CAD and software knowledge to perform virtual waxing at the esthetic region [10]. Interestingly, an opposite finding was seen by a previous study on virtual waxing of posterior single crowns, in which clinical experience was considered more important than CAD experience and software knowledge to obtain the best outcomes [8]. However, the present study also described that even the time to perform virtual waxing was significantly higher for the DENT group. This is also in accordance with the fact that operators of the present study had an additional IOS of the main arch with the conventional temporary crowns, to copy existing anatomy whenever deemed adequate, which was probably better used by the CAD group. This finding is also in agreement with two previous studies that found less occlusal interferences and better outcomes with higher patient satisfaction by copying a pre-existing anatomy during digital waxing, compared to using CAD libraries only [11; 12]. Nevertheless, studies from even previous years presented opposite findings, with significantly better outcomes using a CAD library [13], or even similar results between digital wax patterns generated by a fully automated CAD software program and conventional wax patterns performed by experienced dental technicians [14]. This is the first study suggesting the impact of CAD operator expertise on large anterior CAD-CAM rehabilitations. It is noteworthy that although all crowns manufactured herein were tried in, only the crowns designed by a CAD-CAM technologist were ultimately installed and followed up. The favorable questionnaire outcomes obtained by the crowns designed by the dentist are in agreement with several studies in the literature describing the usefulness and predictability of chairside steps of digital workflows [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25], including for rehabilitation involving dental implant therapy [26; 27; 28; 29; 30; 31; 32; 33]. This is a clinically relevant finding, since the dentist usually plays a major role in the design and manufacture of the CAD-CAM restorations when a chairside digital workflow is performed. However, the present findings contrast with a previous CAD study on single crowns, in which CAD expertise did not affect digital waxing accuracy [8; 9]. On the other hand, our results are in agreement with another CAD study suggesting that CAD expertise affects outcomes of digital wax patterns of anterior CAD-CAM laminate veneers [10]. Two different software programs were used in this study (DentalCAD, Exocad GmbH; and Modellier, Zirkonzahn). However, both software programs have a similar interface designed to be used by CAD-CAM laboratories and technicians. This justified the lack of significant differences between crowns performed with these two CAD software programs, as previously suggested by the literature [10]. The aforementioned citation, however, states that there are significant differences in comparisons between dental commercial CAD-CAM software programs and free open-source CAD-CAM software programs which are not specifically dedicated to the dental field.