Resumen de Effect of temperature on the orthodontic clinical applications of niti closed-coil springs
Eduardo Espinar Escalona, José María Llamas Carreras, José Mª Barrera Mora, Camilo Abalos-Labruzzi, Francisco Javier Gil Mur
NiTi spring coils were used to obtain large deformation under a constant force. The device consists on a NiTi coil spring, superelastic at body temperature, in order to have a stress plateau during the austenitic retransformation during the unloading. The temperature variations induced changes in the spring force.
Objectives: The aim of this study is to investigate the effect of the temperature variations in the spring forces and corrosion behaviour simulating the ingestion hot/cold drinks and food.
Study D esign: The springs were subjected to a tensile force using universal testing machine MTS-Adamel (100 N load cell). All tests were performed in artificial saliva maintained at different temperatures. The corrosion tests were performed according to the ISO-standard 10993-15:2000.
Results: The increase in temperature of 18 o C induced an increase in the spring force of 30%. However, when the temperature returns to 37 o C the distraction force recovers near the initial level. After cooling down the spring to 15 o C, the force decreased by 46%. This investigation show as the temperature increase, the corrosion potential shifts towards negative values and the corrosion density is rising.
Conclusions: The changes of the temperatures do not modify the superelastic behaviour of the NiTi closed-coil springs. The corrosion potential of NiTi in artificial saliva is decreasing by the rise of the temperatures.
