## 4 Discussion  
The present study aimed to evaluate surgical guides without metal sleeves and, simulate, with the aid of FEA, the use of such a dentally supported guide for dental implant insertion in the mandible. The mandible bone was selected due to its highest density [37; 38] and, consequently, due to its highest required drilling force. The digitally designed surgical guide transposes the planned 3D implant position to the surgical field; the perfect fit of the guide on the remaining teeth and the presence of the guiding cylinders (sleeves) play an important role in achieving this purpose. In fully guided surgery, the sleeves can either be acrylic, incorporated into the guide design, or metallic prefabricated sleeves, attached to the custom-fit guide [14]. The use of the surgical guides in daily practice ensures accurate implant placement, increases the probability of successful treatment outcomes, allows predictable flapless surgery and immediate loading, and reduces the risk for technical and biological complications [13; 39; 40]. However, static implant-guided surgery is not without possible risks related to deviations between the planned implant position and the final clinical outcome [41]. One of the major risks of inaccuracy is guide fracture during drilling for implant bed preparation. In a systematic review of complications associated with guided implant surgery, [PERSON] et al. identified the fracture of the surgical guide as a common intraoperative complication, with an incidence rate between 6.7% and 9.7% [41]. The fully resin surgical guide became a major trend in the last few years due to its advantages, such as easier customization, even in the posterior dental arch with less interdental space, low manufacturing cost, and great accessibility without jeopardizing implants insertion accuracy [13]. In spite of the great number of clinical studies performed on resin guides for dental implant insertion, a limited number of studies analyzed the behavior of the surgical guide during its use for implant bed preparation [17; 18; 42; 43] and none investigated the behavior of a tooth-supported, extensively used guide. Among the published studies, one evaluated a resin guide for the insertion of a mini implant aiming to restore a central maxillary incisor [18]. The authors proposed a guide with an open-frame design, customized for use in restoring the anterior maxilla. The performed FEA revealed the fact that maximum equivalent stress was recorded at the junction between the guide support and the guide base, and the maximum displacement (with a value of 0.297 mm) occurred in the area of the guide cylinder [18], which is different from the present study, mainly due to the different design of the guide but also to the way in which it was loaded. The more robust guide used in our study had a considerably lower maximum displacement (0.002 mm), Figure 7b-d illustrating the localization of the maximum displacement and its propagation. Another study by [PERSON] et al. [17] performed a FEA analysis using ANSYS Workbench software on a surgical guide for mandibular reconstruction with integrated implants. The guide was designed using Blue Sky Plan 4 software, and the guide support was dental solely on the mesial side, the mucosal distal support not being considered. The resin guide was proven to withstand the forces occurring during the surgery. The maximum deformation was registered at the distal part of the drill cylinder, and von Mises stress was the highest in the area of the tooth adjacent to the sleeve, as could be expected [17]. [PERSON] et al. [43] investigated, using FEA with Ansys 5.0 software and experimental simulation, the temperature distribution in the drilling site when preparing for dental implant placement with a surgical guide. They concluded that, to avoid bone overheating, improved cooling methods are required and the drill should be regularly withdrawn during drilling.