Effect of changing intraoral temperature on the mechanical properties of clear aligner material in vitro

The aim of this study is to evaluate the mechanical properties of thermoplastic materials. The materials were evaluated in a simulated intraoral environment in this study. Tensile tests on six different thermoplastic products were performed at room temperature and after the thermoforming process, which simulated the intraoral environment. The materials were supplied in the form of a square with a thickness of 0.76 mm, and samples were obtained by laser cutting this square. The samples were inserted into the thermal cycle device in order to mimic the temperature changes that will occur in the oral environment when hot food and beverages is consumed with clear aligners in vitro. These samples, which had been aged for 1.000 thermal cycles, were then tensile tested. There are a total of 30 samples, with 5 samples in each of the six groups. Tensile tests were used to determine the modulus of elasticity, tensile strength and elongation at break of the samples and stress-strain curve analysis was performed. According to the results of the study, after thermocycling, the elastic modulus of CA PRO and GT Flex materials increased. When the stress-strain curves were analyzed, it was seen that the stretching of each material against the force after thermal cycling decreased. The mechanical properties of clear aligner materials are affected by factors other than temperature. It has been discovered that simulating the intraoral environment, which includes the effect of human saliva, is critical in understanding the mechanical properties of these materials. Given these findings, it is believed that in vivo human studies on the mechanical properties of clear aligners are required.