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KJO Korean Journal of Orthodontics

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pISSN 2234-7518
eISSN 2005-372X
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Korean J Orthod

Published online April 22, 2022

Copyright © The Korean Association of Orthodontists.

Comparison of dimensional accuracy between direct-printed and thermoformed aligners

Nickolas Koeniga , Jin-Young Choib , Julie McCraya, Andrew Hayesa, Patricia Schneidera, Ki Beom Kima

aDepartment of Orthodontics, Saint Louis University, Saint Louis, MO, USA
bDepartment of Orthodontics, Graduate School of Dentistry, Kyung Hee University, Seoul, Korea

Correspondence to:Ki Beom Kim.
Professor and Chair, Department of Orthodontics, Saint Louis University, 3320 Rutger St, St. Louis, MO 63104, USA.
Tel +1-314-977-8367 e-mail kkim8@slu.edu

Nickolas Koenig and Jin-Young Choi contributed equally to this work as co-first authors.

Received: October 26, 2021; Revised: January 18, 2022; Accepted: January 19, 2022

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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 FLXTM (n = 12) and Essix ACETM (n = 12), and direct-printed aligners were printed using Tera HarzTM 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 XTM 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 FLXTM aligners ranged from 0.076 ± 0.057 mm to 0.260 ± 0.089 mm and those in the Essix ACETM 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 ACETM, 0.188 ± 0.074 mm for Zendura FLXTM, 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.

Keywords: Aligner, Physical property, Resin, Three-dimensional scanner

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Korean J Orthod

Published online April 22, 2022

Copyright © The Korean Association of Orthodontists.

Comparison of dimensional accuracy between direct-printed and thermoformed aligners

Nickolas Koeniga , Jin-Young Choib , Julie McCraya, Andrew Hayesa, Patricia Schneidera, Ki Beom Kima

aDepartment of Orthodontics, Saint Louis University, Saint Louis, MO, USA
bDepartment of Orthodontics, Graduate School of Dentistry, Kyung Hee University, Seoul, Korea

Correspondence to:Ki Beom Kim.
Professor and Chair, Department of Orthodontics, Saint Louis University, 3320 Rutger St, St. Louis, MO 63104, USA.
Tel +1-314-977-8367 e-mail kkim8@slu.edu

Nickolas Koenig and Jin-Young Choi contributed equally to this work as co-first authors.

Received: October 26, 2021; Revised: January 18, 2022; Accepted: January 19, 2022

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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 FLXTM (n = 12) and Essix ACETM (n = 12), and direct-printed aligners were printed using Tera HarzTM 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 XTM 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 FLXTM aligners ranged from 0.076 ± 0.057 mm to 0.260 ± 0.089 mm and those in the Essix ACETM 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 ACETM, 0.188 ± 0.074 mm for Zendura FLXTM, 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.

Keywords: Aligner, Physical property, Resin, Three-dimensional scanner