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It was the purpose of this study to analyze ad compare the mechanical properties of orthodontic open coil springs. Four variable factors were presented-wire diameter(.008",.009",.001"), lumen size(.030", .032", .036"), arch wire size and shape(.016" round, .016"×.022" rect.) and alloy type(HiT Ⅱ, Elgiloy, Sentalloy). The total 104 specimens were divided into 13 groups, and compression test was performed on an Instron test machine. The load-deflection curve of each open coil spring was obtained, from which, the load-deflection relations, stiffnesses, percent recoveries were computed statistically.The results were obtained as follows: 1. When the lumen size of the coil spring remained constant, stiffness and percent recovery increased as the wire diameter increased. 2. When the wire diameter of the coil spring remained constant, stiffness and percent recovery decreased as the lumen size increased.3. The effect of size and shape of arch wire on the coil spring was not statistically significant. 4. In alloy types, stiffness was the greatest in HiT Ⅱ(55.21), Elgiloy(42.61) and Sentalloy(7.74) in that order. Sentalloy exhibited superior percent recovery and long range of action.
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