## 4 Discussion
### Evaluation of Geometrical Accuracy and Surface Roughness  
After evaluating the geometrical accuracy of the models, we observed differences in the 3D deviation maps and the statistical parameters. Manufacturing the models as three separate fragments significantly improved their accuracy. The deviations for these modelsranged from \(\pm\)0.22 mm to \(\pm\)0.32 mm when measured using the measuring arm-laser head system and from \(\pm\)0.26 mm to \(\pm\)0.32 mm when measured using the Atos II Triple Scan system. However, the deviation range for the pelvic part model manufactured in one piece was more significant, at \(\pm\)0.6 mm for the measuring arm-laser head system and \(\pm\)0.5 mm for the Atos II Triple Scan system. The increase in deviation values for models manufactured in one piece led to the generation of more support material, which was then mechanically removed after the manufacturing process. Moreover, manufacturing the model in the open workspace of the 3D printer significantly raises material shrinkage. Differences also arise from using two different systems and digitization methods. The increase in deviation values for the single-piece manufactured pelvic model is linked to the challenges encountered in the measurement process. It was notably simpler and faster to perform the measurement process on three pieces of pelvic geometry. This was also due to the more favorable orientation of the model in the measurement space of the systems. Based on current research, the maximum deviations in the accuracy of manufactured anatomical models from PLA material are consistent with those reported in publications [66; 67] when the models are made in three separate fragments. However, when a pelvic model is made in one piece, the deviation values differ significantly from the typical range of \(\pm\)0.25 mm to \(\pm\)0.3 mm. However, this publication's comparisons of geometrical accuracy results mainly concern anatomical structures made of PLA material for planning procedures in the craniofacial region. To date, no such analyses have been developed for pelvic anatomical structures. When manufacturing models using the additive MEX method, the researchers identified the most critical parameters responsible for PLA surface roughness as layer thickness [68], build orientation [69], printing speed [68], nozzle diameter [69], and temperature [69]. We carefully selected the best 3D printing parameters based on published research to accurately represent the surface roughness of the models. This was incredibly challenging for the pelvic parts model, which was manufactured as a single piece. In the conducted studies, the acetabulum area was 3D printed in two orientations: on the part of the pelvis model manufactured in one piece. As a result, the amplitude parameters used to assess surface roughness were higher compared to a single model covering only the acetabulum area. The surface roughness of surgical templates made of PLA material and used in the pelvic region has not been evaluated yet. Previous research on PLA materials has mainly focused on simple geometric models and typically uses 2D [70; 71] or 3D profile methods [72; 73] to assess the surface roughness of such specimens.