Chemical and mechanical characteristics of contemporary thermoplastic orthodontic materials


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Australasian Orthodontic Journal

Australian Society of Orthodontists

Subject: Dentistry, Orthodontics & Medicine


ISSN: 2207-7472
eISSN: 2207-7480





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VOLUME 31 , ISSUE 2 (November 2015) > List of articles

Chemical and mechanical characteristics of contemporary thermoplastic orthodontic materials

Alexandros Alexandropoulos / Youssef S. Al Jabbari / Spiros Zinelis / Theodore Eliades *

Citation Information : Australasian Orthodontic Journal. Volume 31, Issue 2, Pages 165-170, DOI:

License : (CC BY 4.0)

Published Online: 15-August-2021



Aim: The aim of the present study was to characterise the chemical and mechanical properties of contemporary thermoplastic orthodontic materials.

Materials and methods: Four thermoplastic materials were tested: Clear Aligner (Scheu-Dental), ACE and A+ (Dentsply), and Invisalign (Align Technology). Eight appliances were fabricated from each material and a small portion from each was analysed by ATR-FTIR spectroscopy. The appliances were cut and, following metallographic grinding and polishing, were subjected to instrumented indentation testing (IIT) employing a Vickers indenter. Martens Hardness (HM), Indentation Modulus (EIT), Elastic to Total Work Ratio (elastic index (ηIT)) and Indentation Creep (CIT) were determined according to ISO 14577-1. The mean values of the mechanical properties were statistically analysed by one way ANOVA and Tukey Kramer multiple comparison test at a = 0.05.

Results: ATR-FTIR analysis identified that Invisalign was a polyurethane-based material, whereas the others were based on polyester, polyethylene glycol terephthalate (PETG). Invisalign showed higher hardness and modulus values, a slightly higher brittleness and lesser creep resistance compared with the PETG-based products.

Conclusions: The materials tested showed significant differences in their chemical structure and mechanical properties and therefore differences in their clinical behaviour are anticipated.

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