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. 2020 May 10;8(2):47.
doi: 10.3390/dj8020047.

Mechanical Properties of Thermoplastic Polymers for Aligner Manufacturing: In Vitro Study

Francesco Tamburrino  1 , Vincenzo D'Antò  2 , Rosaria Bucci  2 , Giulio Alessandri-Bonetti  3 , Sandro Barone  1 , Armando Viviano Razionale  1
Affiliations

Mechanical Properties of Thermoplastic Polymers for Aligner Manufacturing: In Vitro Study

Francesco Tamburrino et al. Dent J (Basel). .

Abstract

The use of metal-free thermoplastic materials plays a key role in the orthodontic digital workflow due to the increasing demand for clear aligner treatments. Three thermoplastic polymers commonly used to fabricate clear aligners, namely Duran®, Biolon® and Zendura®, were investigated to evaluate the effect of thermoforming (T.), storage in artificial saliva (S.A.S.) and their combination on their mechanical properties. Elastic modulus and yield stress of the specimens were characterized. Each material was characterized for each condition through tensile tests (ISO527-1). The results showed that thermoforming does not lead to a significant decrease in yield stress, except for Zendura® that showed about a 30% decrease. An increase of the elastic modulus of Duran® and Zendura®, instead, was observed after thermoforming. The same increase was noticed for the yield stress of Duran®. For S.A.S. specimens, the elastic modulus generally decreases compared to supplier condition (A.S.) and simply thermoformed material. A decrease of yield stress, instead, is significant for Zendura®. The results demonstrated that the impact of the operating conditions on the mechanical properties can vary according to the specific polymer. To design reliable and effective orthodontic treatments, the materials should be selected after their mechanical properties are characterized in the simulated intraoral environment.

Keywords: mechanical properties; orthodontic aligners; simulated oral environment; thermoplastic polymers.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Thermoformed material after waterjet cutting (a) and resulting specimens (b).
Figure 2
Figure 2
Specimen geometry and dimensions.
Figure 3
Figure 3
Specimen clamping during tensile test by Universal Instron Testing Machine 5500R.
Figure 4
Figure 4
Mean value of elastic modulus (a) and tensile yield stress (b) for each material and test condition (D.S., A.S., T., S.A.S.). The percentage of increment or decrement after T. and S.A.S. with respect to A.S. is shown.
Figure 5
Figure 5
Representative stress-strain curves of Duran, Biolon and Zendura specimens: A.S., T., S.A.S.
See this image and copyright information in PMC

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