## 5 Discussion
\begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{(**c**)} \\
**CEREC® OMNICAM** & **Scan with Saliva** & **Scan without Saliva** \\ \hline
**Mean** & 505.0450 & 89.2950 \\ \hline
**SD** & 33.6800 & 16.6857 \\ \hline
**SEM** & 10.6506 & 5.2765 \\ \hline
**N** & 10 & 10 \\ \hline \hline \end{tabular} (a) The two-tailed \(p\) value is less than 0.0001; By conventional criteria, this difference is considered to be extremely statistically significant. The mean of Group One minus Group Two equals 315.3050; 95% confidence interval of this difference: From 270.4026 to 360.2074t = 14.7527; df = 18; standard error of difference = 21.373. (b) The two-tailed \(p\) value is less than 0.0001; By conventional criteria, this difference is considered to be extremely statistically significant. The mean of Group One minus Group Two equals 275.5700; 95% confidence interval of this difference: From 254.0908 to 297.0492; t = 26.9540; df = 18; standard error of difference = 10.224. (c) The two-tailed \(p\) value is less than 0.0001; By conventional criteria, this difference is considered to be extremely statistically significant. The mean of Group One minus Group Two equals 415.7500; 95% confidence interval of this difference: From 390.7785 to 440.7215; t = 34.9783; df = 18; standard error of difference = 11.886.  
\end{table} 
Table 13: _Cont._differences between scanning systems. Similar results were highlighted by [PERSON] et al. [21], after measuring the accuracy of four intraoral scanners, suggesting the limited applicability of IOS only in precise setting, including prosthetic treatments. Interestingly, a study conducted by [PERSON] et al. [23] on three intraoral scanners revealed an error of the accuracy directly proportional with the size of the scanned surface. Further studies focusing on the accuracy of scans of single teeth have shown that the trueness and precision values ranged between 19.2 \(\upmu\)m and 27.9 \(\upmu\)m, and 10.8 \(\pm\) 1.8 \(\upmu\)m, respectively. Additionally, studies evaluating the accuracy of quadrant scans reported values about 35 and 13 \(\upmu\)m of trueness and precision, respectively [17; 18; 19]. A large number of studies have been in recent years to try the reliability and practicability of intraoral scanners, but most of them were carried out with dry models. Few studies have been conducted focusing on the accuracy of intraoral scanner images considering the oral environment and the effect of contamination of saliva and other aspects, such as humidity, intraoral temperature, and so on. [PERSON] et al. shown the contribution of saliva to the inaccuracy of digital impression [24]. This study used test models and devices that led to the detection of dental impression reproducing oral environment conditions. However, several factors that alter the final result (blood, non-homogeneous finishing lines, depth of non-uniform gingival sulcus) were not included. The 360\({}^{\circ}\) chamfer preparation was chosen because it allows a better view of the finishing margin [24; 25; 26]. This type of finishing margin was only of the iuxta and extra gingival type, but in this study, it was deliberately placed under the gum to investigate, in the presence of artificial saliva, the limitations that the IOS have in identifying the finish line [25]. CEREC(r) Omnicam showed a lower overall accuracy both in the absence and in the presence of saliva with significant differences higher than the other two IOS examined only in the presence of saliva. TRIOS(r) 3 and CS 3600 showed an important loss of accuracy only in the presence of saliva and lower compared to CEREC(r) Omnicam. In accordance with the previous literature, the negative influence of the presence of saliva was highlighted for each scan [19; 24; 25; 26; 27; 28; 29]. This is important in the long-term success of the final restoration. Our analysis makes additional reference to the potential of IOS.