## 4 Discussion  
Freehand dental implantology depends on the manual skills of the operator, particularly for the axial implant shifting to what is prosthetically required [23]. An average angular deviation of 3.04\({}^{\circ}\) (ranging from 0.4-6.3\({}^{\circ}\)) and 7.03\({}^{\circ}\) (ranging from 0.7-21.3\({}^{\circ}\)) has  
Figure 4: Box-plots showing the comparison of the two operators relative to the mean values from the three methods evaluation for E point (**A**), A point (**B**), and angular deviation (**C**). \begin{table}
\begin{tabular}{c c c c c c} \hline
**Operator** & **Coef** & **Standard Error** & \(t\) & **[Conf. Interval 95\%]** & \(p\) **Value** \\ \hline
1 & \(-\)1.271402 & 0.29 & \(-\)4.42 & \(-\)2.19 & \(-\)0.36 & 0.021 \\
2 & \(-\)1.30442 & 0.47 & \(-\)2.80 & \(-\)2.79 & 0.18 & 0.068 \\ \hline \end{tabular}
\end{table} 
Table 5: Linear regression model for the correlation of the sequence of the model preparation and the operator error in implant placement. been reported for s-CAI and traditional treatment, respectively [24]. [PERSON] et al. reported that 19.2% of the freehand-placed implants were bearing cement-retained prostheses compared to 100% of screw-retained super-structures on fixtures inserted with digital guides [6]. An overall accuracy value with s-CAI systems has been reported as \(\leq\)1 mm for all linear evaluations and \(\leq\)5\({}^{\circ}\) for angular shifting [4; 25]. Provided there is the correct procedure for realizing the digital template, the principal reason for the higher precision of the s-CAI could be that the human error is reduced. The present study tried to investigate the possible relevance of human expertise intended to enhance the accuracy and reduce the operative timing as derived from the repetition of a specific practical activity over time. The method followed aimed to eliminate, as much as possible, the factors interfering with the univocal interpretation of the data. Since the present study was undertaken \"in vitro\", it was not affected by the variables of clinical practice that would not have been reduced by using an operative guide and allowed a novice operator to carry out the procedure independently. The models used in this trial reproduced similar edentulous mandibular situations with the same complexity level. The flowchart for guide manufacturing was simplified to minimize the risk of procedural mistakes and a bone-supported device was planned without an opposite dental arcade and the soft tissues feature. Since the guides' application to the model was performed by the expert dentist and accurately controlled, the possible bias related to an error in this phase was prevented. The present trial results are, on the other hand, poorly attributable to flapless approaches where soft tissue scanning is mandatory. The major accuracy for the expert operator recorded reported in this study confirms what has been reported in in vitro trials [2; 26; 27; 28] while clinical studies are inconsistent [29; 30]. One study reported more accuracy with the guided digital system than with the free-hands systems when used by novices [2]. An average of 1.12 mm and a maximum value of 4.5 mm at the entry point, an average of 1.39 mm and a maximum value of 7.1 mm at the apex point, and an average axis shifting of 3.89\({}^{\circ}\), and a maximum value of 21.16\({}^{\circ}\) were recorded in in vivo studies reported in a literature review [4]. [PERSON] et al. reported 1.00 mm, 1.23 mm, and 3.13\({}^{\circ}\) for coronal, apical, and angular deviations respectively, in another clinical literature review about the flapless technique [7]. [PERSON] et al. recorded, in vivo, a mean angular deviation of 2.04 degrees and mean coronal, central, and apical linear deviations of 0.68 mm, 0.72 mm, and 0.82 mm, respectively [29]. The present study's overall deviations were lower than those in the literature studies with patients, particularly for angular shifting, both for expert and inexpert operators, regardless of evaluation methods.