## 4 Discussion
investigated the influence of rescanning mesh holes with different diameters (2, 4, and 6 mm) using the Trios 4 IOS (3 Shape, Copenhagen, Denmark), showing that the 6 mm group had the lowest trueness and precision. Regarding the influence of rescanning repetitions, they concluded that there were no significant differences between the groups with the same mesh hole diameter. The overall conclusions of the study were that the higher the number and diameter of the rescanned areas, the lower the accuracy [20]. [PERSON] et al. performed a similar in vitro study using the Trios 3 IOS (3 Shape, Copenhagen, Denmark) on full arch scans and with mesh holes of 12 mm placed on the occlusal surfaces of the left second first molar, incisal edges of the central incisors, and the right first molar for one of the test groups, and on the occlusal surface of the left first molar and left second and first premolars for the second test group. They concluded that rescanning mesh holes combined with the stitching software procedures decreased the trueness and precision of the IOS tested [18]. Another similar in vitro study performed by [PERSON] et al. evaluated the accuracy of another IOS (Medit i500, Medit, Seoul, Republic of Korea), after trimming and rescanning an ear model. The cut-out areas were 2, 5, and 8 mm. The conclusions drawn were in accordance with the other studies regarding the trueness. However, they reported that the precision values were relatively unaffected by the rescanning process [19]. The majority of the research states that the clinically acceptable marginal gap falls between 100 and 120 \(\upmu\)m [21; 22; 23; 24; 25]. Based on this clinically permissible range, a number of prior studies have evaluated the fitness of fixed prostheses [22; 26; 27; 28; 29], but as the obtained values varied, it is challenging to establish an objectively and universally accepted value for clinically acceptable differences when it comes to the marginal fit and accuracy of a digital impression [30]. Based on the approach of the previously mentioned research, we suggest that the resulting trueness and precision differences in the present study, being smaller than 20 \(\upmu\)m, could be deemed as clinically negligible. The present study has several limitations. Firstly, the scenario tested was limited to a single full crown preparation and the adjacent area. A larger area comprised of multiple and/or different preparations as well as a full arch scan could render different results and changes in the accuracy of the scans. Larger scanned areas could also mean a higher chance of overlapping data, which would greatly alter the results. In the case of the in vivo scenario, the trueness analysis relies heavily on the capability of the conventional impression to produce a reference model as closely and accurately to the real intraoral prosthetic plane as possible, and certainly more accurate than the IOS scans with which it is compared. Within the present study, we took all the measures that were in our power to ensure this desideratum, but nevertheless different impression materials or different impression protocols could render more or less accurate reference models. Additional research and studies are advised to be conducted on this subject to better comprehend the influence of the scanning and rescanning protocol on the accuracy of the resulted digital impression.