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Article
Do the Mechanical and Chemical Properties of InvisalignTM Appliances Change After Use? A Retrieval Analysis
European Journal of Orthodontics
  • T. Gerard Bradley, Marquette University
  • Lauren Teske, Marquette University
  • George Eliades, University of Athens
  • Spiros Zinelis, University of Athens
  • Theodore Eliades, University of Zurich
Document Type
Article
Language
eng
Format of Original
5 p.
Publication Date
1-1-2016
Publisher
Oxford University Press
Original Item ID
DOI: 10.1093/ejo/cjv003
Disciplines
Abstract

Aim: To investigate the mechanical and chemical alterations of Invisalign appliances after intraoral aging.

Materials and methods: Samples of Invisalign appliances (Align Technology, San Jose, California, USA) were collected following routine treatment for a mean period of 44±15 days (group INV), whereas unused aligners of the same brand were used as reference (group REF). A small sample from the central incisors region was cut from each appliance and the buccal surface was analysed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy (n = 5). Then the appliances were cut (n = 25) and embedded in acrylic resin, ground/polished in a grinding polishing machine, and the prepared surfaces were subjected to Instrumented Indentation Testing under 4.9 N load. Force-indentation depth curves were recorded for each group and the following parameters were calculated according to ISO 14577-1; 2002 specification: indentation modulus (E IT), elastic to total work ratio also known as elastic index (ηIT), Martens Hardness (HM), and indentation creep (C IT) The mean values of the mechanical properties were statistically analysed by unpaired t-test (a = 0.05).

Results: ATR-FTIR analysis confirmed the urethane based structure of the appliances, without important chemical differences attributed to the aging process. INV group showed significantly lower E IT (REF: 2466±20, INV: 2216±168MPa), HM (REF: 119±1, INV: 110±6 N mm−2) and higher ηIT (REF: 40.0±0.3, INV: 41.5±1.2%), and C IT (REF: 3.7±0.2 INV: 4.0±0.1%). The increase in ηIT indicates that INV is a more brittle than REF, whereas the increase in C IT, a decrease in creep resistance.

Conclusion: Despite the lack of detectable chemical changes, intraoral aging adversely affected the mechanical properties of the Invisalign appliance.

Comments

Accepted version. European Journal of Orthodontics, Vol. 38, No. 1 (2016): 27-31. DOI. © The Author 2015. Published by Oxford University Press on behalf of the European Orthodontic Society. Used with permission.

Citation Information
T. Gerard Bradley, Lauren Teske, George Eliades, Spiros Zinelis, et al.. "Do the Mechanical and Chemical Properties of InvisalignTM Appliances Change After Use? A Retrieval Analysis" European Journal of Orthodontics (2016) ISSN: 1460-2210
Available at: http://works.bepress.com/t_bradley/14/