The effect of heat sterilization on the surface topography and the tensile properties in various nickel titanium wires including a Korean product

Kim, Byoung; Nahm, Dong Seok; Yang, Won Sik

Abstract

The purpose of this study is to investigate the changes of mechanical properties and surface topography of various nickel titanium wires after heat sterilization for recycling with quantitative method. The materials used were four kinds of nickel titanium orthodontic wires including a Korean product. Experimental specimens were treated with two kinds of heat sterilization methods; dry heat (180degrees C, 60snin) and autoclave (121degrees C, 15-20psi, 30min). Mechanical properties were evaluated by tensile test with Instron 4466 (load cell capacity : 1000 kg, cross head speed : 5mm/min, grip distance : 40mm, in room temperature). Surface topography of various wires was compared with each other qualitatively by using scanning electron microscopy and quantitatively by using profilometer. The findings were analyzed statistically with student t-tests. The results were as follows; 1. Neither method of heat sterilization hod any effects on tensile properties of the nickel-titanium wires used in this experiment. 2. Before heat sterilization, the surface smoothness was highest in Optimalloy, followed by Align and Sentailoy, with NiTi showing the lowest smoothness value. 3. In surface topography, Align and Optimalloy were not influenced by heat sterilization. NiTi, on the other hand, had increased roughness after dry heat sterilization and Sentalloy showed the same tendency after each of the two heat sterilization procedures.