Analysis of the thickness of 3-dimensional-printed orthodontic aligners

Introduction: This study aimed to investigate the effect of digitally designed aligner thickness on the thickness of the corresponding 3-dimensional (3D)-printed aligner. Methods: Digitally designed aligners of 3 different thicknesses (0.500 mm, 0.750 mm, and 1.000 mm) were 3D printed in 2 different resins-Dental LT (n = 10 per group) and Grey V4 (n = 10 per group)-using a stereolithography format 3D printer. The Dental LT aligners were coated with a contrast spray and scanned with an optical scanner. The Grey V4 aligners were scanned before and after the application of the spray. Aligner scans were superimposed onto the corresponding digital design file. Average wall thickness across the aligner for each specimen was measured with metrology software. Results: Superimpositions showed that 3D-printed aligners were thicker overall than the corresponding design file. The Dental LT aligners had the largest thickness deviation, whereas the Grey V4 without spray had the smallest. For the 0.500-mm, 0.750-mm, and 1.000-mm groups, Dental LT average thickness deviation from the input file was 0.254 +/- 0.061 mm, 0.267 +/- 0.052 mm, and 0.274 +/- 0.034 mm, respectively, and average thickness differences between the Grey V4 with and without spray was 0.076 +/- 0.016 mm, 0.070 +/- 0.036 mm, and 0.080 +/- 0.017 mm, respectively. These results indicate that the excess thickness in the Dental LT groups could not be attributed to spray alone. Conclusions: Fabrication of clear aligners directly by 3D printing with the workflow applied resulted in an increased thickness that may deleteriously affect the clinical utility of the aligners.