Korean J Orthod.  2022 Jul;52(4):249-257. 10.4041/kjod21.269.

Comparison of dimensional accuracy between direct-printed and thermoformed aligners

Affiliations
  • 1Department of Orthodontics, Saint Louis University, Saint Louis, MO, USA
  • 2Department of Orthodontics, Graduate School of Dentistry, Kyung Hee University, Seoul, Korea

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 FLX TM (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.

Keyword

Aligner; Physical property; Resin; Three-dimensional scanner

Figure

  • Figure 1 Anatomical landmarks on the reference model. Incisal/occlusal: mid-incisal edge point of the lateral incisors (MI), midpoint on the central groove of the second premolars (PG), mesio-lingual cusp tips of the first molars (ML). Mid-crown: functional axis of clinical crown points of central incisors (FACC), midpoint on the palatal surfaces of the first premolars (MP), the buccal pit of the second molars (BP). Gingival: the gingival zenith of the central incisors (GZ), the highest point on the palato-gingival margin of the first premolars (HP), the central point on the gingival margin of the first molars (MC).

  • Figure 2 Aligner mesh (purple) superimposed over the master stereolithography (STL) mesh (blue) by using the best-fit algorithm from Geomagic® Control XTM (3D Systems, Morrisville, NC, USA). Some portions of the aligner mesh are behind the master STL (– values), while some are in front (+ values).

  • Figure 3 Representative heatmaps of an Essix ACETM (Dentsply Sirona, Sarasota, FL, USA) aligner, a Zendura FLXTM (Zendura Dental, Fremont, CA, USA) aligner, and a direct-printed aligner (from left to right). Green areas represent areas where the aligner did not deviate from the model by more than 0.25 mm while bluer areas represent deviations in the negative direction and redder areas represent deviations in the positive direction.

  • Figure 4 Modified Bland–Altman plots of landmark measurements for all samples. Different colors denote different samples. A, Zendura FLXTM (Zendura Dental, Fremont, CA, USA) aligners. B, Essix ACETM (Dentsply Sirona, Sarasota, FL, USA) aligners. C, Direct-printed aligners.


Reference

1. Rosvall MD, Fields HW, Ziuchkovski J, Rosenstiel SF, Johnston WM. 2009; Attractiveness, acceptability, and value of orthodontic appliances. Am J Orthod Dentofacial Orthop. 135:276.e1–12. discussion 276–7. DOI: 10.1016/j.ajodo.2008.07.011. PMID: 19268820. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=61349197684&origin=inward.
2. Weir T. 2017; Clear aligners in orthodontic treatment. Aust Dent J. 62 Suppl 1:58–62. DOI: 10.1111/adj.12480. PMID: 28297094. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85015210290&origin=inward.
3. Jindal P, Juneja M, Siena FL, Bajaj D, Breedon P. 2019; Mechanical and geometric properties of thermoformed and 3D printed clear dental aligners. Am J Orthod Dentofacial Orthop. 156:694–701. DOI: 10.1016/j.ajodo.2019.05.012. PMID: 31677678. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85074126931&origin=inward.
4. Edelmann A, English JD, Chen SJ, Kasper FK. 2020; Analysis of the thickness of 3-dimensional-printed orthodontic aligners. Am J Orthod Dentofacial Orthop. 158:e91–8. DOI: 10.1016/j.ajodo.2020.07.029. PMID: 33131570. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85094557479&origin=inward.
5. Wan Hassan WN, Yusoff Y, Mardi NA. 2017; Comparison of reconstructed rapid prototyping models produced by 3-dimensional printing and conventional stone models with different degrees of crowding. Am J Orthod Dentofacial Orthop. 151:209–18. DOI: 10.1016/j.ajodo.2016.08.019. PMID: 28024776. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85006874553&origin=inward.
6. Mantovani E, Castroflorio E, Rossini G, Garino F, Cugliari G, Deregibus A, et al. 2018; Scanning electron microscopy evaluation of aligner fit on teeth. Angle Orthod. 88:596–601. DOI: 10.2319/120417-827.1. PMID: 29911907. PMCID: PMC8183126. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85054490515&origin=inward.
7. Lombardo L, Palone M, Longo M, Arveda N, Nacucchi M, De Pascalis F, et al. 2020; MicroCT X-ray comparison of aligner gap and thickness of six brands of aligners: an in-vitro study. Prog Orthod. 21:12. DOI: 10.1186/s40510-020-00312-w. PMID: 32390068. PMCID: PMC7211786. PMID: bcb319f3655c432fbba7d300c6451bad. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85084295596&origin=inward.
8. Chisari JR, McGorray SP, Nair M, Wheeler TT. 2014; Variables affecting orthodontic tooth movement with clear aligners. Am J Orthod Dentofacial Orthop. 145(4 Suppl):S82–91. DOI: 10.1016/j.ajodo.2013.10.022. PMID: 24680028. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84897406264&origin=inward.
9. Bowman SJ. 2017; Improving the predictability of clear aligners. Semin Orthod. 23:65–75. DOI: 10.1053/j.sodo.2016.10.005. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85007298586&origin=inward.
10. Holm C, Tidehag P, Tillberg A, Molin M. 2003; Longevity and quality of FPDs: a retrospective study of restorations 30, 20, and 10 years after insertion. Int J Prosthodont. 16:283–9. PMID: 12854793. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0141833152&origin=inward.
11. Johal A, Sharma NR, McLaughlin K, Zou LF. 2015; The reliability of thermoform retainers: a laboratory-based comparative study. Eur J Orthod. 37:503–7. DOI: 10.1093/ejo/cju075. PMID: 25431104. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84943423875&origin=inward.
12. Cole D, Bencharit S, Carrico CK, Arias A, Tüfekçi E. 2019; Evaluation of fit for 3D-printed retainers compared with thermoform retainers. Am J Orthod Dentofacial Orthop. 155:592–9. DOI: 10.1016/j.ajodo.2018.09.011. PMID: 30935614. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85063452753&origin=inward.
13. Kim SY, Shin YS, Jung HD, Hwang CJ, Baik HS, Cha JY. 2018; Precision and trueness of dental models manufactured with different 3-dimensional printing techniques. Am J Orthod Dentofacial Orthop. 153:144–53. DOI: 10.1016/j.ajodo.2017.05.025. PMID: 29287640. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85039151375&origin=inward.
14. Cho JH, Yoon HI, Han JS, Kim DJ. 2019; Trueness of the inner surface of monolithic crowns fabricated by milling of a fully sintered (Y, Nb)-TZP block in chairside CAD-CAM system for single-visit dentistry. Materials (Basel). 12:3253. DOI: 10.3390/ma12193253. PMID: 31590370. PMCID: PMC6803933. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85073979538&origin=inward.
15. Peters MC, Delong R, Pintado MR, Pallesen U, Qvist V, Douglas WH. 1999; Comparison of two measurement techniques for clinical wear. J Dent. 27:479–85. DOI: 10.1016/S0300-5712(99)00027-5. PMID: 10507203. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0033195285&origin=inward.
16. Yamada J, Maeda Y. 2007; Thermoforming process for fabricating oral appliances: influence of heating and pressure application timing on formability. J Prosthodont. 16:452–6. DOI: 10.1111/j.1532-849X.2007.00222.x. PMID: 17672835. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=35348875505&origin=inward.
17. Nakano H, Kato R, Kakami C, Okamoto H, Mamada K, Maki K. 2019; Development of biocompatible resins for 3D printing of direct aligners. J Photopolym Sci Technol. 32:209–16. DOI: 10.2494/photopolymer.32.209. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85074986710&origin=inward.
18. Zinelis S, Panayi N, Polychronis G, Papageorgiou SN, Eliades T. 2021; Comparative analysis of mechanical properties of orthodontic aligners produced by different contemporary 3D printers. Orthod Craniofac Res. doi: 10.1111/ocr.12537. [Epub ahead of print]. DOI: 10.1111/ocr.12537. PMID: 34569692. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85116242317&origin=inward.
19. Unkovskiy A, Schmidt F, Beuer F, Li P, Spintzyk S, Kraemer Fernandez P. 2021; Stereolithography vs. direct light processing for rapid manufacturing of complete denture bases: an in vitro accuracy analysis. J Clin Med. 10:1070. DOI: 10.3390/jcm10051070. PMID: 33806627. PMCID: PMC7961584. PMID: 043b3b862d79411d9fda705373acbed6. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85104575352&origin=inward.
20. Su TS, Sun J. 2015; Comparison of repeatability between intraoral digital scanner and extraoral digital scanner: an in-vitro study. J Prosthodont Res. 59:236–42. DOI: 10.1016/j.jpor.2015.06.002. PMID: 26211702. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84944175820&origin=inward.
21. Park ME, Shin SY. 2018; Three-dimensional comparative study on the accuracy and reproducibility of dental casts fabricated by 3D printers. J Prosthet Dent. 119:861.e1–861.e7. DOI: 10.1016/j.prosdent.2017.08.020. PMID: 29475753. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85042173626&origin=inward.
22. Ryokawa H, Miyazaki Y, Fujishima A, Miyazaki T, Maki K. 2006; The mechanical properties of dental thermoplastic materials in a simulated intraoral environment. Orthod Waves. 65:64–72. DOI: 10.1016/j.odw.2006.03.003. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=33745489798&origin=inward.
23. Schuster S, Eliades G, Zinelis S, Eliades T, Bradley TG. 2004; Structural conformation and leaching from in vitro aged and retrieved Invisalign appliances. Am J Orthod Dentofacial Orthop. 126:725–8. DOI: 10.1016/j.ajodo.2004.04.021. PMID: 15592222. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=10044243470&origin=inward.
24. Eliades T, Pratsinis H, Athanasiou AE, Eliades G, Kletsas D. 2009; Cytotoxicity and estrogenicity of Invisalign appliances. Am J Orthod Dentofacial Orthop. 136:100–3. DOI: 10.1016/j.ajodo.2009.03.006. PMID: 19577155. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=67649397393&origin=inward.
25. Brezniak N. 2008; The clear plastic appliance: a biomechanical point of view. Angle Orthod. 78:381–2. DOI: 10.2319/0003-3219(2008)078[0381:TCPA]2.0.CO;2. PMID: 18251593.
26. Hahn W, Dathe H, Fialka-Fricke J, Fricke-Zech S, Zapf A, Kubein-Meesenburg D, et al. 2009; Influence of thermoplastic appliance thickness on the magnitude of force delivered to a maxillary central incisor during tipping. Am J Orthod Dentofacial Orthop. 136:12.e1–7. discussion 12–3. DOI: 10.1016/j.ajodo.2008.12.015. PMID: 19577136. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=67649394209&origin=inward.
27. Wheeler T. 2005; Invisalign clinical trials needed. Am J Orthod Dentofacial Orthop. 127:527. DOI: 10.1016/j.ajodo.2005.03.006. PMID: 15877024. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=18844387642&origin=inward.
28. Qi HJ, Boyce MC. 2005; Stress-strain behavior of thermoplastic polyurethanes. Mech Mater. 37:817–39. DOI: 10.1016/j.mechmat.2004.08.001. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=18444403157&origin=inward.
29. Lombardo L, Arreghini A, Maccarrone R, Bianchi A, Scalia S, Siciliani G. 2015; Optical properties of orthodontic aligners--spectrophotometry analysis of three types before and after aging. Prog Orthod. 16:41. DOI: 10.1186/s40510-015-0111-z. PMID: 26582007. PMCID: PMC4651973. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84982803827&origin=inward.
30. Kim KY, Ahn HW, Kim SH, Nelson G. 2017; Effects of a new type of clear overlay retainer on occlusal contacts. Korean J Orthod. 47:207–12. DOI: 10.4041/kjod.2017.47.3.207. PMID: 28523247. PMCID: PMC5432442. PMID: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85032449220&origin=inward.
Full Text Links
  • KJOD
Actions
Cited
CITED
export Copy
Close
Share
  • Twitter
  • Facebook
Similar articles
Copyright © 2023 by Korean Association of Medical Journal Editors. All rights reserved.     E-mail: koreamed@kamje.or.kr