## 4 Discussion  
The results of the present in vivo and in vitro study showed that rescanning and overlapping data, as well as trimming and rescanning a surface of a digital model and the different data acquisition protocol, influence the accuracy of the IOS. The present study raised several questions: \"Accuracy wise, is it better to scan a single time the interest area leaving the IOS's software to fill in the remaining mesh holes or is it better to scan multiple times the same area until complete geometry data acquisition?\". Another question was \"in which way cropping an area followed by a consecutive scan influences the accuracy of a digital impression?\" The simulated scenarios were selected in order to observe which option is the most reliable way to obtain an accurate digital impression. Moreover, these scenarios are implemented frequently during the digital impression stage and in some cases all of them can be applied on the same intraoral scan. The study was conducted in both in vivo and in vitro scenarios. Initially, the purpose was to evaluate these variables in a controlled environment followed by clinical data corroboration. The results showed that in both in vivo and in vitro cases the accuracy  
Figure 8: Boxplot displaying the values of the in vivo case. (**a**) Trueness values. (**b**) Precision values. Figure 7: Boxplot displaying the values of the in vitro case. (**a**) Trueness values. (**b**) Precision values. values had a similar pattern. The best trueness was displayed by the \"SINGLESCAN\" group, and the trueness seemed to decrease as more data were overlapped in the other groups. When accounting for precision, the \"SINGLESCAN\" group was the least precise in both cases as there were more surfaces left unrecorded, especially on the proximal areas, during this protocol, in which the holes in the mesh were filled by the software and probably differed between the scans. The \"RESCAN\" group, having the least unrecorded areas, seemed the most precise. There was an inconsistency between the in vivo and in vitro cases regarding precision as the \"DELETE & RESCAN\" group was slightly better performing in the in vitro scenario, closely followed by the \"RESCAN\" group with a 3.4 \(\upmu\)m decrease in precision, while in the in vivo scenario the \"RESCAN\" group was considerably superior. The study presents high numerical values of the deviation between the IOS meshes and the reference meshes; this varied in the case of trueness from 100 to 170 \(\upmu\)m, which could be considered clinically unacceptable. This results from the fact that a large area of the mesh was analyzed, and more surfaces produced a higher deviation than in the case of analyzing only the prepared tooth area, especially the tissue areas that were recorded with poorer accuracy. The overall trueness differences between the analyzed groups were no larger than 17 \(\upmu\)m in the in vitro scenario and no larger than 11 \(\upmu\)m in the in vivo case, indicating a small difference between the tested scanning protocols. The precision seems to be influenced a greater amount by the scanning protocol as the overall differences reached 35 \(\upmu\)m.  
The location of the evaluated scans was in the posterior arch. This scenario was intentionally selected since lateral proximal areas usually are harder to reach with the IOS's tip and in some cases mesh holes may pass unnoticed. The influence of the preparation geometry was also observed. The in vitro abutment was prepared with a chamfer finish line while the in vivo case, due to conservative reasons, was prepared with a feather edge finish line. In both situations, the trueness values were similar and precision values differed slightly, showing that the equigingival positioning of the type of preparation had little to no influence on the accuracy of digital impressions in the present study. [PERSON] et al.