Influence of constant strain on the elasticity of thermoplastic orthodontic materials

What is it about?

The aim of this study was to identify a physical property suitable for evaluating the orthodontic force by analyzing the physical properties of thermoplastic materials. Four thermoplastic materials were used: Essix A+® Plastic (EA), DURAN® (DU), Erkodur (ER), and Essix C+® Plastic (EC). Finite element analysis (FEA), a water absorption test, constant strain loading test, X-ray diffraction (XRD) and Fourier transformation infrared spectroscopy analysis were conducted. FEA found a significant correlation between the elastic modulus and the orthodontic force. The water absorption of EC was significantly smaller than the other materials. EC showed no elastic modulus change. The XRD pattern indicated that EC was a crystalline polymer. FEA of thermoplastics showed that the elastic modulus is suitable for the evaluation of orthodontic force. The crystalline thermoplastic EC demonstrated a stable elastic modulus even under strain in a wet environment, suggesting the advantage of its use as an orthodontic aligner material.

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Why is it important?

An in silico 3D FEA reflecting the physical properties of commercially available thermoplastic showed that the elastic modulus can be used to evaluate the orthodontic force. A crystalline thermoplastic EC with low water absorption demonstrated a stable elastic modulus even under strain in a wet environment, suggesting there are advantages of using EC as the material in orthodontic aligners.

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