온도 변화가 활성화된 교정용 니켈-티타늄 코일 스프링의 힘에 미치는 영향

Abstract

The purpose of this study was to evaluate the effectiveness of overactivation in lowering force level of NiTi coil springs. 12 kinds of NiTi springs were tested, and 5 springs were used for each kind. First, Load/deflection tests were performed and then temperature change tests were performed at 7 mm extension in the condition with or without 5 mm overactivation. The temperature was changed from 37℃ to 5℃～70℃. Also, DSC (Differential Scanning Calorimetry) tests were performed to evaluate transitional temperature ranges. The results were as follows. 1. In the load/deflection tests, Sentalloy springs (blue, yellow, red), and Jinsung blue, Tomas lite, Nitinol light, and G4 ex. light showed superelasticity. Align medium showed greatest permanent deformation of 0.24 mm after 12 mm extension. 2. Jinsung blue, Tomas lite, Nitinol light, and G4 ex. light did not show transformation at DSC tests of -80℃～100℃. 3. Overactivation decreased the force of all NiTi springs except G4 ex. light and G&H ultralight which do not have stress hysteresis. But, after temperature changes, the forces of springs without overactivation decreased, and the forces of springs with overactivation increased, so that the two forces became similar. The effectiveness of overactivation of NiTi coil springs can be valid only before intraoral temperature changes take place. Also, caution is required to prevent permanent deformation of NiTi coil springs during overactivation.