# Accuracy Comparison among 3D-Printing Technologies to Produce Dental Models
## 3 Results  
All 3D printers could manufacture the dental casts successfully from the same STL file. Average printing time was 11 hours, and average number of layers was 930 (approximately 130 mL of light-cured resin).  
Normality assumption was not confirmed (\(p<0.05\)), therefore non-parametric tests comparisons were assessed. Both interobserver reproducibility and intra-observer reliability were confirmed as ICC values ranged between 0.87 and 0.96 (\(p=0.01\)). No significant difference was found in the comparison between observers in all measurements performed with the different models. Figure 3 shows the estimated marginal median control and test measurements. The Stratasys 3D printer achieved the greatest accuracy, as the digital caliper measurements of the respective dental casts were the most similar to the control measurements performed in the CAD software.  
For the left posterior buccal-lingual width measurement, Anycubic obtained the lowest median and standard error values (12.160 \(\pm\) 0.075 mm), followed by Stratasys (12.288 \(\pm\) 0.138 mm), Form 2 (12.306 \(\pm\) 0.117 mm), Miicraft (12.436 \(\pm\) 0.066 mm), and Phrozen (12.548 \(\pm\) 0.039 mm). For the right posterior buccal-lingual width measurement, the Anycubic (13.500 \(\pm\) 0.067 mm) obtained the lowest values, again followed by Stratasys (13.683 \(\pm\) 0.114 mm), Form 2 (13.705 \(\pm\) 0.167 mm), Miicraft (13.840 \(\pm\) 0.079 mm), and Phrozen (13.930 \(\pm\) 0.109 mm), respectively. For the anterior buccal-lingual width, Anycubic obtained the lowest values (8.065 \(\pm\) 0.046 mm), followed by Form 2 (8.190 \(\pm\) 0.033 mm), Miicraft (8.285 \(\pm\) 0.060 mm), Stratasys (8.298 \(\pm\) 0.132 mm), and Phrozen (8.370 \(\pm\) 0.056 mm). The larger measurement was the maximum horizontal width and lowest measurement values was the anterior buccal-lingual width. The lowest value of trueness was obtained for anterior nasal spine: nasopalatine foramen measurement for Miicraft printer (0.128 mm).  
Figure 2: Example of digital and analog measures taken in the 3D analysis software. (**a**). Left posterior buccal–lingual width with markers; (**b**). Right posterior buccal–lingual width with markers; (**c**). anterior buccal–lingual width with markers; (**d**). Distance between anterior nasal spine and infraorbital foramen; (**e**). Distance between tip of cusps of teeth 13 and 23; (**f**). Distance between tips of cusps of teeth 14 and 24. Test measurements with digital caliper (1) and control digital measurements on the CAD software in occlusal view (2).  
The highest value of trueness was obtained for anterior buccal-lingual width measurement for Phrozen (0.230 mm). The lowest values of precision were reached by Form 2 (0.002 mm) and Micraft (0.002 mm) for maximum horizontal width. The highest value of precision was obtained by Anycubic (0.035 mm) for the anterior nasal spine: nasopalatine foramen measurement. Friedmann test revealed no significant differences among all 3D printers for trueness and precision (\(p>0.05\)). However, pairwise Wilcoxon test comparisons revealed statistically significant differences between Stratasys versus Anycubic printers (\(p=0.025\)) and Anycubic versus Form 2 (\(p=0.048\)).