Defense Date


Document Type


Degree Name

Master of Science in Dentistry



First Advisor

Eser Tüfekçi, DDS, MS, PhD, MSHA

Second Advisor

Dr. Rami Ammoun, DDS, MS, CDT, FACP

Third Advisor

Sompop Bencharit, DDS, MS, PhD

Fourth Advisor

Caroline Carrico, PhD


Purpose: To evaluate the accuracy of three-dimensionally (3D) printed aligners compared to conventional vacuum-formed thermoplastic aligners with varying levels of dental crowding.

Methods: Digital intraoral scans of 10 different cases were assigned to their respective groups (n=10, each, 30 total) as follows: no crowding (control), moderate crowding, and severe crowding. Using 3Shape software, digital aligner samples were created in standard tessellation language (STL) file format and randomly 3D printed. The same STL files of each case were also sent to a dental laboratory for the fabrication of vacuum-formed samples, which is the current technology used for manufacturing aligners. The intaglio surfaces of aligners in both groups were scanned using cone beam computed tomography to create STL files, which were compared to the original STL files of the cases using Geomagic Control X software. Absolute deviations from the original file and root mean square values were recorded. A Kruskal-Wallis test was conducted to analyze the difference in average deviation and t-test was repeated for the RMS measure. Significance level was set at 0.05.

Results: The amount of crowding did not have an effect on the accuracy of aligners manufactured using 3D printing or conventional vacuum-forming techniques. 3D printed aligners showed less deviation than the vacuum-formed samples (0.1139mm vs 0.1330mm; p-value=0.0007). There was also a statistically significant difference in the variance between the two methods (p-value=0.0014), with a higher variance among aligners manufactured with the vacuum-forming technique than 3D printing method.

Conclusion: 3D aligners printed directly from an STL file exhibited better precision and trueness than the aligners fabricated using the conventional vacuum-forming technique. Since accuracy is defined as a combination of precision and trueness, it is concluded that direct printing from an STL file can be used to manufacture aligners.


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