Comparison of dimensional accuracy between direct-printed and thermoformed aligners

OBJECTIVE: The purpose of this study was to evaluate and compare the dimensional accuracy between thermoformed and direct-printed aligners. METHODS: Three types of aligners were manufactured from the same reference standard tessellation language (STL) file thermoformed aligners were manufactured using Zendura FLX(TM) (n = 12) and Essix ACE(TM) (n = 12), and direct-printed aligners were printed using Tera Harz(TM) TC-85DAP 3D Printer UV Resin (n = 12). The teeth were not manipulated with any tooth-moving software in this study. The samples were sprayed with an opaque scanning spray, scanned, imported to Geomagic(®) Control X(TM) metrology software, and superimposed on the reference STL file by using the best-fit alignment algorithm. Distances between the aligner meshes and the reference STL file were measured at nine anatomical landmarks. RESULTS: Mean absolute discrepancies in the Zendura FLX(TM) aligners ranged from 0.076 ± 0.057 mm to 0.260 ± 0.089 mm and those in the Essix ACE(TM) aligners ranged from 0.188 ± 0.271 mm to 0.457 ± 0.350 mm, while in the direct-printed aligners, they ranged from 0.079 ± 0.054 mm to 0.224 ± 0.041 mm. Root mean square values, representing the overall trueness, ranged from 0.209 ± 0.094 mm for Essix ACE(TM), 0.188 ± 0.074 mm for Zendura FLX(TM), and 0.140 ± 0.020 mm for the direct-printed aligners. CONCLUSIONS: This study showed greater trueness and precision of direct-printed aligners than thermoformed aligners.