## 4 Discussion  
This systematic review presented several results that, for a better understanding, can be divided according to the different factors analyzed: type of digital prosthetically-derived surgical guides for dental implants, type of support of the surgical guide, method for the elaboration of surgical guides, and number of fixation screws. Each of them will be described below. Type of digital prosthetically-derived surgical guide. The prosthetically guided implant protocol is the process of virtual planning of a dental implant using 3D planning software. This flow requires a wax-up file of the tooth or teeth to be replaced, in conjunction with a CBCT, considering the esthetic, functional, and anatomical criteria of the prosthesis to achieve a correct 3D position of the implant. To answer the question of whether the type of surgical guide used might influence the accuracy of planning and placement of prosthetically guided implants, the types of surgical guides described in the literature were analyzed. The types of implant guides were classified according to the level of guidance (partial or total) and the ability to allow intraoperative changes (static or dynamic). Although the literature has shown that fully guided static surgery provides a more accurate position, a synthesis of the published evidence is necessary to verify whether there is greater efficacy in implant treatment [17, 18]. Digital prosthetically-derived surgical guides for dental implants can be applied using three protocols during surgery: in the fully guided or restrictive surgical protocol, the guide is used from the first drilling in the bone to the final implant placement [19]. In the partially guided surgical protocol, the digital prosthetically-derived surgical guides are used only to form the bone socket for the implant and are then removed for the placement of the implant. Finally, surgical guidance is used only in the first pilot drilling of the osteotomy. As shown in Table 2, this systematic review focused on fully guided surgical protocols because their accuracy is significantly greater, and they have demonstrated superiority over other protocols [20, 21]. According to the articles reviewed, the transfer of the planned position of the implant with respect to its clinical environment is more accurate when using a static-guided technique, in which a fully guided workflow is performed. The deviation values in each study performed were minimal, not exceeding 1.03 mm of overall apical deviation. However, it can be suggested that a safety zone of at least 1.5 mm should be established in digital planning. Type of support of the digital prosthetically-derived surgical guides for dental implants  
According to this review, the type of support influences the accuracy of digital prosthetically-derived surgical guides. Depending on the type of support, the guides can be bone-supported, mucosa-supported, or tooth-supported. Theoretically, anatomical differences in the teeth, bone, and mucosa can lead to differences in the accuracy of the guides. Bilateral tooth-supported surgical guides provide better retention and stability, as they are anchored in hard tissue and, therefore, offer greater accuracy. Bilateral guides are indicated for patients whose teeth are mesial and distal to the dedentulous area. On the other hand, unilateral tooth-supported guides are indicated for patients with distal extension edentulism because they provide efficient retention. Bone-supported guides are placed over the exposed alveolar ridge by means of a full-thickness mucoperiosteal flap operation and secured with fixation screws. The positioning of this type of support is affected by the surgical incision and elevation of the surrounding tissue, so the accuracy is relatively low. Mucosal-supported guides are indicated for totally edentulous patients or patients with very few residual teeth. These guides are stabilized by means of fixation screws [22, 23].