## 4 Discussion
observed that multiple implants placed with the same guide showed higher mean deviations than single implants [26]. This has also been observed by [PERSON] et al. in 2006 [27]. Previous studies have used preoperative and postoperative CBCT scan datasets to measure angular deviation [16; 28]. However, a limitation exists in this protocol because all software has an internal error which is different from the real measurement. CBCT scan datasets may differ due to different orientations of objects. In our study, a specific guide was created to correctly position the jaws. A \"scan body\" of the implant placed in the drilled path could have been used to allow for the addition of scan datasets. However, this method requires the body scans to be stable in the drilled path. The distance measurements were manually calculated by two blinded observers (an endodontist and a general practitioner familiar with the software). Although this methodology was based on a preliminary study, this may have led to small errors in the calculations. The use of computer software to automatically calculate the deviation between planned and performed drill path by registering preoperative and postoperative CBCT scans may be relevant for future studies [29]. Nowadays, most guide systems are using resin 3D-printed surgical guides with metal sleeves for drill guidance. However, these resin 3D-printed surgical guides have some limitations. Common issues reported with surgical guides are lack of fit and stability, limited irrigation possibilities, and the lack of visibility due to the intrinsic volume of the guide [30; 31]. Today, there are alternatives to this approach for 3D-printed surgical guides or guided surgery systems [17; 32]. Thanks to the development of the relevant technology, in particular for partial denture removal due to a need to improve precision and the satisfaction of patients, the cost of such guides recently decreased to be comparable with resin guides. The advantage of the SMG is the open frame that allows visibility and irrigation while maintaining stability. Interestingly, SMGs offer the advantage to potentially eliminate the sleeves. The presence of the sleeve, in fact, forces the surgeon to use long drills available only in surgical kits specifically dedicated to guided surgery. [PERSON] et al. showed that surgical guides without metallic sleeves were more accurate than a conventional guide with a metallic sleeve [18]. Although sleeves were used in this study, one of the advantages of a metal guide is that it is possible to use it without a sleeve, thus avoiding this bias [17]. The next step will be to design, produce, and assess SMGs without sleeves. This study was a proof of concept using a simple ex vivo model. Although the model did not fully replicate conditions in vivo (pig teeth are larger than human teeth and tooth shapes decrease the stability of the guide), this ex vivo model offers advantages. The bone density of a young pig jaw is similar to that of a human mandible [33]. According to [PERSON] et al., this is a crucial factor when assessing the accuracy of a surgical guide [25]. This simulation model is easy to handle and cost-effective, and different experiments may be performed (CBCT, histology) because repeated freeze-thaw cycles do not alter the bone [34].