Analysis, Comparison and Evaluation of the Microhardness and Elasticity of Thermoformed Polyurethane Sheets Used for Treatment with Aligners in Different Brands

International Journal of Mechanical Engineering

© 2025 by SSRG - IJME Journal

Volume 12 Issue 6

Year of Publication : 2025

Authors : Karen Zafra-Ubillus, Kelly Achachao-Almerco, Sandra Pastor-Arenas, Jorge Infantes-Vargas, Oscar Alcázar-Aguilar, Alicia Alva-Mantari, Gina León-Untiveros

10.14445/23488360/IJME-V12I6P105

How to Cite?

Karen Zafra-Ubillus, Kelly Achachao-Almerco, Sandra Pastor-Arenas, Jorge Infantes-Vargas, Oscar Alcázar-Aguilar, Alicia Alva-Mantari, Gina León-Untiveros, "Analysis, Comparison and Evaluation of the Microhardness and Elasticity of Thermoformed Polyurethane Sheets Used for Treatment with Aligners in Different Brands," SSRG International Journal of Mechanical Engineering, vol. 12,  no. 6, pp. 52-61, 2025. Crossref, https://doi.org/10.14445/23488360/IJME-V12I6P105

Abstract:

The present in vitro study aimed to analyze the mechanical (flexural and Microhardness) and optical (color stability) properties of three commercial thermoformed polyurethane sheets used in orthodontics: Essix ACE,® Duran® and Taglus®. These properties, which are crucial for the clinical efficacy of aligners, were evaluated and compared to provide orthodontists with relevant information for selecting the most suitable material for each patient. The results revealed significant differences in mechanical properties between the three brands, suggesting that the choice of material may influence the effectiveness of the treatment. Duran® presented the highest flexural modulus, while Taglus® exhibited the highest Microhardness. Additionally, the color stability of the sheets was evaluated when immersed in different coloring substances, including red wine, orange juice and Fanta®. Red wine produced the greatest color alterations in the materials, a factor to consider for patients. In conclusion, the selection of material for aligner manufacturing should consider not only strength and durability, but also color stability, as well as other factors such as patient comfort. This study provides valuable information on the characteristics of different thermoformed polyurethane sheets, which can be useful for orthodontists to make more informed decisions when selecting the material to manufacture aligners.

Keywords:

Aligners, Orthodontics, Thermoformed sheets, Properties, Stability.

References:

[1] Gabriele Rossini et al., “Efficacy of Clear Aligners in Controlling Orthodontic Tooth Movement: A Systematic Review,” The Angle Orthodontist, vol. 85, no. 5, pp. 881-889, 2015.
[CrossRef] [Google Scholar] [Publisher Link]
[2] Neal D. Kravitz et al., “How well does Invisalign Work? A Prospective Clinical Study Evaluating the Efficacy of Tooth Movement with Invisalign,” American Journal of Orthodontics and Dentofacial Orthopedics, vol. 135, no. 1, pp. 27-35, 2009.
[CrossRef] [Google Scholar] [Publisher Link]
[3] D.M.J. Chang, “Introduction to Invisalign® Smart Technology: Attachments Design, and Recall-Checks,” J Digital Orthod, vol. 54, no. 1, pp. 81-94, 2019.
[Google Scholar] [Publisher Link]
[4] Nickolas Koenig et al., “Comparison of Dimensional Accuracy between Direct-Printed and Thermoformed Aligners,” Korean Journal of Orthodontists, vol. 52, no. 4, pp. 249-257, 2022.
[CrossRef] [Google Scholar] [Publisher Link]
[5] Rosaria Bucci et al., “Thickness of Orthodontic Clear Aligners after Thermoforming and After 10 Days of Intraoral Exposure: A Prospective Clinical Study,” Progress in Orthodontics, vol. 20, no. 1, pp. 1-8, 2019.
[CrossRef] [Google Scholar] [Publisher Link]
[6] Adham Skaik et al., “Effects of Time and Clear Aligner Removal Frequency on the Force Delivered by Different Polyethylene Terephthalate Glycol-Modified Materials Determined with Thin-Film Pressure Sensors,” American Journal of Orthodontics and Dentofacial Orthopedics, vol. 155, no. 1, pp. 98-107, 2019.
[CrossRef] [Google Scholar] [Publisher Link]
[7] Luca Lombardo et al., “Optical Properties of Orthodontic Aligners-Spectrophotometry Analysis of Three Types Before and After Aging,” Progress in Orthodontics, vol. 16, pp. 1-8, 2015.
[CrossRef] [Google Scholar] [Publisher Link]
[8] Alexander Edelmann et al., “Analysis of the Thickness of 3-Dimensional-Printed Orthodontic Aligners,” American Journal of Orthodontics and Dentofacial Orthopedics, vol. 158, no. 5, pp. e91-e98, 2020.
[CrossRef] [Google Scholar] [Publisher Link]
[9] Isabella Pratto, Mauro Carlos Agner Busato, and Paulo Rodrigo Stival Bittencourt, “Thermal and Mechanical Characterization of Thermoplastic Orthodontic Aligners Discs After Molding Process,” Journal of the Mechanical Behavior of Biomedical Materials, vol. 126, 2022.
[CrossRef] [Google Scholar] [Publisher Link]
[10] Hiltrud Dasy et al., “Effects of Variable Attachment Shapes and Aligner Material on Aligner Retention,” The Angle Orthodontist, vol. 85, no. 6, pp. 934-940, 2015.
[CrossRef] [Google Scholar] [Publisher Link]
[11] Kazem Dalaie, Seyyed Mostafa Fatemi, and Samin Ghaffari, “Dynamic Mechanical and Thermal Properties of Clear Aligners after Thermoforming and Aging,” Progress in Orthodontics, vol. 22, no. 1, pp. 1-11, 2021.
[CrossRef] [Google Scholar] [Publisher Link]
[12] Bijan Golkhani et al., “Variation of the Modulus of Elasticity of Aligner Foil Sheet Materials Due to Thermoforming,” Journal of Orofacial Orthopedics, vol. 83, no. 4, pp. 233-243, 2022.
[CrossRef] [Google Scholar] [Publisher Link]
[13] Hussein Shakir Saleh Al Noor, and Sami Kadhum. Al-Joubori, “Comparison of the Hardness and Elastic Modulus of Different Orthodontic Aligners' Materials,” International Journal of Medical Research and Pharmaceutical Science, vol. 5, no. 9, pp. 19-25, 2018.
[CrossRef] [Google Scholar] [Publisher Link]
[14] Paolo Albertini et al., “Stress Relaxation Properties of Five Orthodontic Aligner Materials: A 14-Day In-Vitro Study,” Bioengineering, vol. 9, no. 8, pp. 1-11, 2022.
[CrossRef] [Google Scholar] [Publisher Link]
[15] Spiros Zinelis et al., “Comparative Analysis of Mechanical Properties of Orthodontic Aligners Produced by Different Contemporary 3D Printers,” Orthodontics & Craniofacial Research, vol. 25, no. 3, pp. 336-341, 2022.
[CrossRef] [Google Scholar] [Publisher Link]
[16] Jeong-Hyun Ryu et al., “Effects of Thermoforming on the Physical and Mechanical Properties of Thermoplastic Materials for Transparent Orthodontic Aligners,” The Korean Journal of Orthodontics, vol. 48, no. 5, pp. 316-325, 2018.
[CrossRef] [Google Scholar] [Publisher Link]
[17] Prashant Jindal et al., “Mechanical and Geometric Properties of Thermoformed and 3D Printed Clear Dental Aligners,” American Journal of Orthodontics and Dentofacial Orthopedics, vol. 156, no. 5, pp. 694-701, 2019.
[CrossRef] [Google Scholar] [Publisher Link]
[18] Aljazi H. Aldweesh et al., “Comparison of Mechanical Properties and Color Stability of Various Vacuum-Formed Orthodontic Retainers: An in Vitro Study,” The Saudi Dental Journal, vol. 35, no. 8, pp. 953-959, 2023.
[CrossRef] [Google Scholar] [Publisher Link]
[19] Priyanka Venkatasubramanian et al., “Color Stability of Aligner Materials on Exposure to Indigenous Food Products: An in-Vitro Study,” Journal of Dental Research, Dental Clinics, Dental Prospects, vol. 16, no. 4, pp. 221-228, 2022.
[CrossRef] [Google Scholar] [Publisher Link]
[20] Valeria Daniele et al., “Color Stability, Chemico-Physical and Optical Features of the Most Common PETG and PU- Based Orthodontic Aligners for Clear Aligner Therapy,” Polymers, vol. 14, no. 1, pp. 1-18, 2022.
[CrossRef] [Google Scholar] [Publisher Link]