## 4 Discussion  
The accuracy of digitally planned mini-implant positions is a clinically relevant topic since it represents a prerequisite for the immediate placement of the pre-operatively CAD-CAM fabricated orthodontic appliance. This allows for a reduction in the number of the appointments and, therefore, the overall duration of the orthodontic treatment [25]. Moreover, depending on the location of implant insertion, high accuracy can be crucial to  
Figure 6: Boxplot reporting the angle between the planned and real mini-implant position in the four groups. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Location** & **Group** & **Mean** & **SD** & **Median** & **Min** & **1 st Quart** & **3 rd Quart** & **Max** \\ \hline \multirow{6}{*}{**Category**} & Full-arch/ & \multirow{2}{*}{1.25} & \multirow{2}{*}{0.56} & \multirow{2}{*}{1.22} & \multirow{2}{*}{0.48} & \multirow{2}{*}{0.88} & \multirow{2}{*}{1.64} & \multirow{2}{*}{2.04} \\  & no pre-drilling & & & & & & & \\ \cline{1-1}  & Skeletonized/ & \multirow{2}{*}{1.65} & \multirow{2}{*}{0.62} & \multirow{2}{*}{1.73} & \multirow{2}{*}{0.57} & \multirow{2}{*}{1.36} & \multirow{2}{*}{2.11} & \multirow{2}{*}{2.31} \\  & no pre-drilling & & & & & & \\ \cline{1-1}  & Full-arch/ & \multirow{2}{*}{1.22} & \multirow{2}{*}{0.60} & \multirow{2}{*}{1.15} & \multirow{2}{*}{0.27} & \multirow{2}{*}{0.93} & \multirow{2}{*}{1.49} & \multirow{2}{*}{2.54} \\  & pre-drilling & & & & & & \\ \cline{1-1}  & Skeletonized/ & \multirow{2}{*}{2.09} & \multirow{2}{*}{0.92} & \multirow{2}{*}{2.09} & \multirow{2}{*}{1.02} & \multirow{2}{*}{1.52} & \multirow{2}{*}{2.28} & \multirow{2}{*}{4.65} \\ \cline{1-1}  & pre-drilling & & & & & & & \\ \hline \multirow{6}{*}{**Category**} & Full-arch/ & \multirow{2}{*}{3.04} & \multirow{2}{*}{1.44} & \multirow{2}{*}{2.64} & \multirow{2}{*}{1.38} & \multirow{2}{*}{2.34} & \multirow{2}{*}{3.41} & \multirow{2}{*}{5.73} \\  & no pre-drilling & & & & & & & \\ \cline{1-1}  & Skeletonized/ & \multirow{2}{*}{1.72} & \multirow{2}{*}{1.22} & \multirow{2}{*}{1.26} & \multirow{2}{*}{0.66} & \multirow{2}{*}{1.01} & \multirow{2}{*}{1.99} & \multirow{2}{*}{4.13} \\ \cline{1-1}  & Full-arch/ & \multirow{2}{*}{2.69} & \multirow{2}{*}{1.40} & \multirow{2}{*}{2.10} & \multirow{2}{*}{1.22} & \multirow{2}{*}{1.92} & \multirow{2}{*}{3.13} & \multirow{2}{*}{6.46} \\ \cline{1-1}  & pre-drilling & & & & & & & \\ \hline \multirow{6}{*}{**Category**} & Full-arch/ & \multirow{2}{*}{12.75} & \multirow{2}{*}{6.96} & \multirow{2}{*}{10.54} & \multirow{2}{*}{5.41} & \multirow{2}{*}{8.77} & \multirow{2}{*}{15.22} & \multirow{2}{*}{25.33} \\  & no pre-drilling & & & & & & & \\ \cline{1-1}  & Skeletonized/ & \multirow{2}{*}{8.23} & \multirow{2}{*}{4.24} & \multirow{2}{*}{7.89} & \multirow{2}{*}{2.39} & \multirow{2}{*}{5.47} & \multirow{2}{*}{10.90} & \multirow{2}{*}{14.55} \\ \cline{1-1}  & no pre-drilling & & & & & & & \\ \cline{1-1}  & Full-arch/ & \multirow{2}{*}{12.47} & \multirow{2}{*}{7.23} & \multirow{2}{*}{11.21} & \multirow{2}{*}{1.39} & \multirow{2}{*}{8.92} & \multirow{2}{*}{14.43} & \multirow{2}{*}{31.30} \\ \cline{1-1}  & pre-drilling & & & & & & & \\ \hline \multirow{6}{*}{**Category**} & Full-arch/ & \multirow{2}{*}{11.78} & \multirow{2}{*}{6.04} & \multirow{2}{*}{10.90} & \multirow{2}{*}{4.30} & \multirow{2}{*}{8.94} & \multirow{2}{*}{12.18} & \multirow{2}{*}{31.52} \\ \cline{1-1}  & no pre-drilling & & & & & & & \\ \cline{1-1}  & Skeletonized/ & \multirow{2}{*}{11.78} & \multirow{2}{*}{6.04} & \multirow{2}{*}{10.90} & \multirow{2}{*}{4.30} & \multirow{2}{*}{8.94} & \multirow{2}{*}{12.18} & \multirow{2}{*}{31.52} \\ \cline{1-1}  & pre-drilling & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Descriptive statistic data on the deviation of the mini-implants neck, apex, and angle. Values are reported in mm. avoiding iatrogenic damage to the surrounding structures, including the nerves and roots of the adjacent teeth [29; 30].