Studies Of Mechanical Properities Of Nickel-Titanium Orthodontic Wires

Objective:Nickel-titanium archwire alloys are very important for clinical orthodontics because of their wide elastic range and excellent springback, along with their ability to deliver highly desirable light forces for tooth movement. There are dozens of different wire brands currently on the market. Compared to the literature available abroad,there are few reports about this issue in China. The aim of this study was to characterize three selected commercial NiTi archwiresA .B.C. (A, imported, USA brand; B.C,domestic,China brand) in terms of their transformation behavior, and mechanical properties (at temperatures of 37 degrees Celsius and room temperature ) and changes on mechanical properties after different duration of being put in mouth.Method:Examining the different commercial nickel-titanium orthodontic wire's mechanical properties through 3-point bending tests under controlled stress and different temperature(room temperature and 37℃).Then putting the 0.016 inch C nickel-titanium wires into the patients'mouth for different duration, and then there different bending properties were examined through 3-point bending tests under controlled stress and temperature.Results: 1. The force of the A nickel-titanium orthodontic wire is the smallest at temperatures of 37 degrees Celsius and room temperature.2. The force of the B nickel-titanium is the largest at room temperature and The force of the C nickel-titanium is the largest at temperatures of 37 degrees Celsius. 3. The largest delayed strain was A nickel-titanium orthodontic wire and the smallest delayed strain was B nickel-titanium orthodontic wire.4. At the same local displacement,the force of nickel-titanium orthodontic wire at temperatures of 37 degrees was larger that at room temperature.5. There was statistical significant difference among the 0.016 inch C nickel-titanium wires put into the patients'mouth for different duration.Conclusions: 1. The largest hysterisis was 0.016 inch A nickel-titanium orthodontic wire.2. 0.016 inch A and C nickel-titanium wires were more sensitive to the temperature.3. 0.016 inch B nickel-titanium wire was not sensitive to the temperature.4. There were distinct differences between time and load and hysteresis difference.5. The mechanical property was damping by the duration time in the patients'mouth.