## 2 Materials and Methods  
### Workflow for Surgical Guide Design and Manufacturing  
The manufacturing of a surgical guide for dental implant insertion is based on a set of data collected from the patient. These data are imported into a planning and design software; the future restoration is planned as a virtual wax-up, and based on this and available bone volume, a dental implant is selected from the software's library and its position is set based on the final planned restoration. The surgical guide is custom designed in accordance with the planned implant position using reverse engineering. Depending on the type of support (dental, mucosal, or mixed), additional temporary fixation systems are also designed to improve guide retention. Digital impressions or scanned analog models obtained from analog impressions, cone-beam computed tomography (CBCT), and digital wax-ups of the future restoration are the main data utilized in dental implant positioning planning and static surgical design. There are several pieces of software used for the planning and design of surgical guides, such as Exoplan (Exocad GmbH, Darmstadt, Germany), R2 Gate(tm) (MegaGen, Daegu, Republic of Korea), Blue Sky Bio (LLC, Libertyville, IL, USA), Simplant Pro(tm) (Dentsply, Sweden), ImplantStudio (3 Shape, Copenhagen, Denmark), and so on. The steps of surgical guide planning using R2 Gate software, version 2.0, are presented in Figure 1.  
The planned implant insertion is exported as.rws file (RimWorld game save file) or as a.stl file (stereolithography--a popular 3D printing technology). R2 Ware version 1.1.40201 software uses.rws files for the design of the surgical guide with incorporated sleeves, and the main steps are: (1) remove undercuts; (2) draw boundaries; (3) cut boundaries; (4) set parameters (thickness of the guide and offset--the space between the inner surface of the guide and the surface of the model); (5) window set (for inspecting windows used to ensure that surgical guides fit well on neighboring teeth); and (6) text (for writing the patient's name on the external surface of the guide) (Figure 2a,b). The designed guide (Figure 2c) is usually manufactured with the aid of a 3D printer (additive manufacturing) or, less often, by milling in an acrylic blank (subtractive manufacturing). Due to its ability to reproduce complex structures at reduced cost and reduce material waste, additive manufacturing is the most popular method [21; 22]. The full resin surgical guide is printed using E-Guide Resin (EnvisionTEC GmbH, Gladbeck, Germany) with the Digital Light Processing (DLP) technique, and its fit is checked on the patient's model (Figure 2d) before using it for implant surgery. The same workflow is followed for planning, designing, and manufacturing surgical guides with mucosal or mixed support. Additional transversal pins are required, in certain cases, for guide stabilization. Figure 1: _Cont._  
Figure 1: Surgical guide design in R2 Gate(tm) software, version 2.0: (**a**) DICOM files from CBCT and.stl files of the patient’s corresponding dental arch impression are imported in the software, and a three-point matching is performed; (**b**) a second 3D manual matching of CBCT with the digital model is undertaken; (**c**) design of the digital wax-up; (**d**) for dental implant insertion in the mandible, one extra step, alveolar nerve tracing, is required; (**e**) selecting the adequate implant and 3D positioning spanning according to the final prosthetic restoration and the existing width and height of the bone; (**f**) when planning is performed and approved, the R2 Gate corresponding drill core is selected and the window is positioned on the buccal side; (**g**) the planned implant position is exported as.rws file.