## 4 Discussion  
In this study, the conditions for reducing the metal artifacts generated by dental prosthetics during dental-impression acquisition were analyzed and the iMAR technique was applied to remove the artifacts to generate accurate output via 3D printing. Recent efforts involved the analysis of the surface of the human body using 3D printing and surgical approaches via specific bone registration and symmetrical implants [19, 20, 21]. CT \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **120 kVp 30 mAs** & \multicolumn{3}{c}{**120 kVp 50 mAs**} & \multicolumn{3}{c}{**120 kVp 80 mAs**} \\ \hline  & **Inner Area** & **Outer Area** & **Inner Area** & **Outer Area** & **Inner Area** & **Outer Area** \\ \hline iMAR & \(-448.98\pm 347.59\) & \(-597.77\pm 411.40\) & \(-438.65\pm 344.62\) & \(-575.63\pm 425.25\) & \(-438.66\pm 344.70\) & \(-668.73\pm 374.19\) \\ non iMAR & \(-310.52\pm 298.20\) & \(-271.21\pm 514.26\) & \(-298.42\pm 288.37\) & \(-278.27\pm 461.58\) & \(-266.78\pm 288.31\) & \(-280.73\pm 487.60\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Changes in Hounsfield unit values according to change in current after fixing tube voltage in the artifact area. Figure 4: 3D printing of CT image. (**a**) The selected area for 3D printing in InVesalius 3.1.1 software. (**b**) As a 3D printing product that did not apply iMAR, the artifact was printed as it was (white arrow). (**c**) A 3D-printed product that was iMAR-applied where relatively large portions of artifacts have been removed. However, it was printed in the form of a defect in the inferior part of the metal area. In addition, in the case of the second premolar, it was generated as a defect due to excessive signal loss (arrow). is a medical device that can accurately delineate human anatomy and phase information. Since CT can accurately determine the exact size and position of the human body, it can accurately implement the model and size, which represent the anatomical information of the image [22; 23]. In particular, since CT is expressed in HUs based on the atomic number and density of a substance, it facilitates the extraction of 3D surface information of a specific density for 3D printing protocols [24; 25; 26]. However, metal artifacts represent one of the biggest limitations in 3D printing of CT images. A metal artifact is a filter phenomenon in which the low energy of X-rays is absorbed when X-rays pass through a metallic structure, and the average energy of the X-rays is increased [27]. Therefore, it is expressed in the form of a flash centered on the location of the metal area. As for the artifact, the signal increases in the existing anatomical position, that is, the HUs increase so that the artifact in the form of flashes is inevitably generated in the 3D-printed output. The phantom used in this study was not only the human body structure in which metal artifacts are most commonly generated, but also the teeth, which are a relatively sophisticated structure in the human body. Therefore, in this study, teeth with metal components were used as a target to obtain 3D printing impressions. The method of reducing beam hardening artifacts is commonly used by increasing the tube voltage technically. In this study, as well, it was possible to observe a high artifact reduction effect at high tube voltage during the optimization with reduced artifacts. In the absence of iMAR, the HU values of the inner and outer areas were shown the low as applying a high tube voltage. In the absence of iMAR, the HU values of the inner and outer areas were shown the low as applying a high tube voltage. In the absence of iMAR, the HU values of the inner and outer areas were shown the low as applying a high tube voltage. In the case of images subjected to iMAR, the reduction in metal artifacts at a low tube voltage of 80 kVp was about 200% greater than in iMAR at 120 kVp. Thus, the elimination of artifacts at low tube voltage was higher following iMAR.