A Comparative Study For Different NiTi Wire LDR Test Models

Objective:To compare the differences among the 3 test models according to the load-deflection curve, so as to choose a test model which can be applied for the clinical test. Methods:The load-deflection test of SMART 0.014 inch NiTi wire on the 3-point bending test model(Modle 1), modified 3-point bending test model(Model 2) and acrylic maxilla test model(Model 3) were carried out with an Instron 5567 universal test machine at 37°C. Results:1.For the 0.5mm deflection the load values from different models are statistically different. Loading and unloading values from Model 3 are highest, however values from Model 1 are lowest. None of curves from these models shows plateau plot which represents the superelasticity of the arch wire. 2. For the 2.0mm deflection the load values from Model 2 and 3 are statistically higher than from Model1, and values which descend after 0.9mm deflection in the loading process from Model 3 are lower than Model 1. There is a plateau plot in the unloading process from Model 2. Conclusions:1. The test results of NiTi round arch wire load-deflection rate curve from 3-point bending test model, modified 3-point bending test model and acrylic maxilla test model are different. 2. In respect that the acrylic maxilla model which simulated the clinical situation in which the load-deflection property of NiTi wire is tested as a part of the appliance, moreover, it can reflect the friction between the wire and the brackets, the evaluation from this model is more comprehensive than the other tow models. 3. Acrylic maxilla model can be use to test NiTi wire in the clinic in order to help orthodontist to evaluate the effects of the NiTi wires which are used for the orthodontic treatment.