# Surface Morphology of Three-Dimensionally Printed Replicas of Upper Dental Arches
## 3 Results  
### Cross-Section Model Analysis  
Processing of 3D images resulted in a cluster of points; this is further optimized to compute the polygonal mesh. This model was used for accurate analysis. Inspections were conducted in SW GOM Inspect Professional v8, software which allows advanced analysis of a 3D dimensional cluster of points obtained from the polygonal mesh produced by an optical scanner. The deviations were calculated in the form of color maps (Figure 1); this allowed the creation of inspection sections in cross-section for four printing technologies, SLS, SLA, FDM and PJ (Figure 2).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **SLS** & **SLA** & **FDM** & **PJ** \\ \hline Section 1.dXYZ.1 & 0.000 & 0.039 & 0.226 & 0.000 \\ Section 1.dXYZ.2 & 0.000 & 0.185 & 0.024 & 0.000 \\ Section 1.dXYZ.3 & 0.000 & 0.260 & 0.000 & 0.000 \\ Section 1.dXYZ.4 & 0.000 & 0.845 & 0.000 & 0.008 \\ Section 1.dXYZ.5 & 0.000 & 0.396 & 0.000 & 0.001 \\ Section 1.dXYZ.6 & 0.000 & 0.587 & 0.001 & 0.069 \\ Section 1.dXYZ.7 & 0.000 & 0.329 & 0.039 & 0.758 \\ Section 1.dXYZ.9 & 0.002 & 0.006 & 0.240 & 0.002 \\ Section 1.dXYZ.10 & 0.002 & 0.008 & 0.004 & 0.000 \\ Section 1.dXYZ.11 & 0.001 & 0.267 & 0.307 & 0.018 \\ Section 1.dXYZ.12 & 0.001 & 0.073 & 0.001 & 0.000 \\ Section 1.dXYZ.13 & 0.000 & 0.041 & 0.002 & 0.000 \\ Section 1.dXYZ.14 & 0.001 & 0.162 & 0.000 & 0.000 \\ Section 1.dXYZ.15 & 0.000 & 0.083 & 0.000 & 0.000 \\ Section 1.dXYZ.17 & 0.000 & 0.011 & 0.001 & 0.145 \\ Section 1.dXYZ.18 & 0.000 & 0.659 & 0.081 & 0.630 \\ Section 1.dXYZ.19 & 0.000 & 0.654 & 0.226 & 0.206 \\ Section 1.dXYZ.20 & 0.000 & 0.294 & 0.063 & 0.093 \\ Section 1.dXYZ.21 & 0.000 & 0.154 & 0.005 & 0.790 \\ Section 1.dXYZ.22 & 0.001 & 0.345 & 0.295 & 0.193 \\ Section 1.dXYZ.23 & 0.011 & 0.837 & 0.171 & 0.034 \\ Section 1.dXYZ.25 & 0.003 & 0.001 & 0.929 & 0.000 \\ Section 1.dXYZ.26 & 0.000 & 0.029 & 1.000 & 0.000 \\ Section 1.dXYZ.27 & 0.001 & 0.120 & 0.557 & 0.010 \\ Section 1.dXYZ.28 & 0.000 & 0.004 & 0.000 & 0.000 \\ Section 1.dXYZ.29 & 0.000 & 0.013 & 0.000 & 0.000 \\ Section 1.dXYZ.30 & 0.001 & 0.309 & 0.000 & 0.004 \\ Section 1.dXYZ.31 & 0.000 & 0.049 & 0.000 & 0.012 \\ MEAN & 0.001 & 0.241 & 0.149 & 0.106 \\ STD & 0.002 & 0.254 & 0.263 & 0.223 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Standard deviations of printed models from the nominal model created by individual printing methods (technologies) for 31 sectional planes.  
The current model was evaluated in the Cartesian coordinate system. A three-dimensional object was transformed relative to the nominal model such that the sum of squared deviations of all measured points (i.e., Cloud points) was minimal. The software calculated the perpendicular distance of each transverse point on the actual specimen from CAD data. Blue indicates measured areas that are located below the surface of the CAD (i.e., minus--less material). Red areas are located over the surface of the CAD (i.e., plus--more material). Green areas indicate no abnormalities detected. In assessing the quality of models, a color map based on the direct 2D cut was most important (Figure 2). The sectional plane passed in the same place and intersects all of the teeth in an optimal position (Table 1). In cross-section, it was evident from the measurements that the deviation shifted by approximately 0.1 mm; the accuracy was almost the same or even better than for the classical wet process [12].