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Dynamic mechanical and thermal properties of clear aligners after thermoforming and aging

Authors
  • Dalaie, Kazem1
  • Fatemi, Seyyed Mostafa2
  • Ghaffari, Samin1, 2
  • 1 Shahid Beheshti University of Medical Sciences, Daneshju Boulevard, Velenjak District, Tehran, Iran , Tehran (Iran)
  • 2 Shahid Beheshti University of Medical Sciences, Tehran, Iran , Tehran (Iran)
Type
Published Article
Journal
Progress in Orthodontics
Publisher
Springer Berlin Heidelberg
Publication Date
Jun 28, 2021
Volume
22
Issue
1
Identifiers
DOI: 10.1186/s40510-021-00362-8
Source
Springer Nature
Keywords
Disciplines
  • Research
License
Green

Abstract

BackgroundBased on the role of properties of aligner materials on their efficiency, we aimed to assess their thermomechanical properties after thermoforming and simulated aging.MethodsIn this experimental study, 96 samples of polyethylene terephthalate glycol (PETG) aligners (Duran and Erkodur) were prepared and divided to three groups: control (C), after thermoforming (T), after thermoforming and aging (TA). Thermoforming was done through 3D-printed molds, and aging was exerted by 200 thermal cycles after immersion in 37°C distilled water for 24h. Flexural modulus, hardness, glass transition temperature (Tg), elastic and viscous modulus, and loss factor were evaluated. Two-way ANOVA, T-independent, and Tukey HSD tests were done for statistical analysis and significance level was set to 0.05.ResultsIn both materials, flexural modulus decreased significantly after thermoforming, 88% in Duran and 70% in Erkodur, but did not change significantly after aging. After thermoforming, hardness decreased significantly in both materials (22% in Duran and 7.6% in Erkodur). Dynamic Tg was significantly lower in T and TA in both materials. At all temperatures (25, 37, 55°C) in Duran, the elastic modulus difference was only significant between C and TA, but in Erkodur, it decreased significantly in T, and there was no significant change after aging. Viscous modulus and loss factor showed the same change patterns at all temperatures. In both materials, they increased after thermoforming, but did not change significantly after aging.ConclusionThermoforming had more prominent role than aging in diminishing of thermomechanical properties. In general, Duran had greater thermomechanical stability than Erkodur.

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