## 4 Discussion
conducted a study of the impact of the placement of fixation pins in digital prosthetically-derived surgical guides, analyzing the possible discrepancies between the planned design and the clinical position of the placed implant. They established that the discrepancy was statistically significant for apical and vertical deviation. Guide fixation is recommended for bilateral posterior edentulous spaces. The accuracy of implant placement is improved when the template is fixed with screws, for example, in cases of fully edentulous patients [33; 34]. Only two of the four publications included in this review mentioned the number of fixation pins used in digital prosthetically-derived surgical guides, which were used with dental support in one patient and mucosa support in another patient. According to the articles reviewed, the number of impression pins will depend on the type of support, either tooth-supported or mucosa-supported. It is recommended to use at least two fixation pins in tooth-supported cases and at least three in mucosa-supported cases. In the articles reviewed, there was evidence of greater deviation at the apical level compared to the coronal and vertical deviation of the implants placed. On the other hand, the vertical deviation is the deviation that presented the least variation between the planned and obtained locations. Table 3 shows six parameters that show the deviation between the planned and achieved results. Based on the data available for each article, the global coronal deviation ranged from 0.44 mm to 0.56 mm; the global apical deviation ranged from 0.64 mm to 1.03 mm; the angular deviation ranged from 2.03\({}^{\circ}\) to 2.42\({}^{\circ}\); and the vertical deviation ranged from 0.19 mm to 0.45 mm. It is important to note that some authors did not provide data for all deviation measurements. The values varied among the different studies, underscoring the need for further research with quantitative data. Among the limitations of this review, more databases were not included due to the accessibility of the researchers, nor were articles in other languages and gray literature used. In vivo studies that can compare virtual planning with the final position of dental implants are recommended to obtain more reliable results that solidly support the frequent use of prosthetically guided implants. It is important to emphasize the role of study designs with control groups. It would be very important in future research to include a control group in the same study with respect to the technique of implant placement, using drill guides, restrictive guides, and freehand implant placement surgery. In two of the articles selected in this systematic review, the results are analyzed based on the presence of a different control group in each study. The first article, by [PERSON], compares implant placement using restrictive guidance with a control group performing freehand placement. The results indicate a reduction in discrepancy in all measurements. In [PERSON]'s article, partially digital and fully digital workflows are investigated, showing that procedures with a fully digital protocol, which includes intraoral scanning instead of analog post-impression scanning, have a lower discrepancy between planning and final implant placement. Four articles were finally included after an exhaustive search with inclusion and exclusion criteria. The limited number of articles selected supports the fact that there is scarce scientific literature and evidence on the subject of this systematic review. In addition, the position of the implant and the type of edentulism (total or partial) are not supported by sufficient evidence in the selected articles to draw quantitative conclusions regarding the discrepancy values. Within the limitations of this review, the authors have considered that several results are duplicated in other databases that have already been indexed in the record of what has been reviewed. The heterogeneity of the methodology of the studies should be taken into account, so the bias analysis was fundamental.