Objectives: To investigate the differences in the mechanical properties of seven different commercial clear aligners, such as surface roughness, elastic modulus, tensile strength and chemical modifications of the materials.
Materials and methods: Seven different clear aligner materials used around the world were assessed and their mechanical and optical performance were evaluated. Although Zendura FLX (Bay Materials, Fremont, CA, USA) and CA Pro (Scheu Dental, Iserlohn, Germany) are multilayered materials made from polyethylene terephthalate glycol, it is stated that Zendura FLX contains polyurethane. The tensile properties of thermoplastic materials were determined in accordance with the standard EN-ISO 527-1:2012. A Vickers hardness test was performed to evaluate the hardness of the materials, and Fourier transform infrared spectroscopy was used to analyse their molecular structure. The optical properties were determined using a UV-visible spectrophotometer, and surface roughness was ?measured using an optical profilometer. The data were examined using a one-way analysis of variance and a post hoc Tukey test.
Results: The multilayered Zendura FLX and CA Pro materials were found to have the lowest modulus of elasticity and low tensile strength values. In line with the literature, the material with the highest ?hardness was determined to be ?Zendura. Duran+ (Scheu Dental), CA Pro, GT Flex (Good Fit Technologies, Boston, MA, USA) and GT Pro (Good Fit Technologies) materials were also found to have a smoother surface than the ?others. The Taglus Premium material (Vedia Solutions, Mumbai, India) with the lowest visible UV-visible absorbance value was the most transparent.
Conclusion: Clinical studies should be conducted to confirm the mechanical properties of these seven clear aligner materials.
Keywords: aligners, elastic modulus, hardness, physical properties, thermoplastic
