Comparative analysis of mechanical properties of orthodontic aligners produced by different contemporary 3D printers

Spiros Zinelis; Nearchos Panayi; Georgios Polychronis; Spyridon N Papageorgiou; Theodore Eliades

doi:10.1111/ocr.12537

Comparative analysis of mechanical properties of orthodontic aligners produced by different contemporary 3D printers

Orthod Craniofac Res. 2022 Aug;25(3):336-341. doi: 10.1111/ocr.12537. Epub 2021 Oct 4.

Authors

Spiros Zinelis¹, Nearchos Panayi², Georgios Polychronis¹, Spyridon N Papageorgiou³, Theodore Eliades³

Affiliations

¹ Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.
² Private practice, Limassol, Cyprus.
³ Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.

Abstract

Objective: The aim of this study was to compare the mechanical properties of orthodontic aligners among different commercially available 3D printing devices.

Materials and methods: Five 3D printers (Ka:rv LP 550, Swinwon; "KAR"), (L120, Dazz 3D; "L12"), (MiiCraft 125, Miicraft Jena; "MIC"), (Slash 2, Uniz; "SLS") and (Pro 95, SprintRay; "PRO") were used to prepare orthodontic aligners with dental resin (Tera Harz TC-85DAW, Graphy). The central incisors of each aligner were cut, prepared and evaluated in terms of Martens-Hardness (HM), indentation-modulus (E_IT ) and elastic-index (η_IT ) as per ISO14577-1:2002. Force-indentation curves were recorded and differences among printers were checked with generalized linear regressions (alpha=5%).

Results: Statistically significant differences were seen for all mechanical properties (P < .05), which were in descending order: HM (N/mm² ) as median (Interquartile Range [IQR]): SLS 108.5 (106.0-112.0), L12 103.0 (102.0-107.0), KAR 101.5 (97.5-103.0), MIC 100.0 (97.5-101.5) and PRO 94.0 (93.0-96.0); E_IT (MPa) as mean (Standard Deviation [SD]): SLS 2696.3 (124.7), L12 2627.8 (73.5), MIC 2566.2 (125.1), KAR 2565.0 (130.2) and PRO 2491.2 (53.3); and η_IT (%) as median (IQR): SLS 32.8 (32.3-33.1), L12 31.6 (30.8-32.3), KAR 31.3 (30.9-31.9), MIC 30.5 (29.9-31.2) and PRO 29.5 (29.1-30.0). Additionally, significant differences existed between liquid crystal display (LCD) and digital light processing (DLP) printers for HM (P < .001), E_IT (P = .002) and η_IT (P < .001), with aligners from the former having higher values than aligners from the latter printer.

Conclusion: Under the limitations of this study, it may be concluded that the mechanical properties of 3D-printed orthodontic aligners are dependent on the 3D printer used, and thus, differences in their clinical efficacy are anticipated.

Keywords: 3D printing; clear aligners; instrumented indentation testing; mechanical properties.

Publication types

Review

MeSH terms

Hardness
Materials Testing
Printing, Three-Dimensional*