Abstract

With the development of new materials related to clear aligners, the physical properties are improving, and the clinical performance of the devices is expected to improve. Clear aligners require constant, controlled force on the teeth to achieve the desired tooth movement. However, unlike superelastic wires for orthodontic treat ment, clear aligner materials are characterized by significant short-term or long-term stress relaxation after installation of the device. In addition, clear aligners are a complex manufacturing process that requires creating a tooth model and trimming the aligners, and various degrees of shrinkage and expansion may occur during the thermoforming process or direct printing of device. These changes can affect the thickness or fit of each tooth area and make it difficult to achieve the clinical treatment goals of clear aligner. Recently, multi-layered clear orthodontic products with improved physical properties have been introduced to increase the predictability of aligner treatment, and with the recent introduction of direct printing materials, innovative manufacturing methods for clear orthodontic devices have become possible. As shape memory prop erties have been reported among direct printing materials, interest in related materials is increasing. In this issue, we will introduce the latest materials related to clear aligners and explain the physical and biological properties that clinicians need to know for proper use.