| Objective:This study was to investigate the load/deflection characteristics of 0.018" stainless steel archwire(3M-Unitek) formed 4mm reverse-curve arch after different patterns of heat treatment, and compare with not heat treated control group.Method:12cm 0.018" stainless steel archwire was formed to the standard Edgewise arch with 4mm reverse-curve as samples. All samples in experiment group were heat treated by different temperatuare and/or time and then evaluated by Instron appliance, record the load/deflection stress of each group. The control group was evaluated in the same method.Results:(1) Group 2,3,4,5 compared to control group, the load/deflection stress had statistically sagnificant difference.(2) Between the heat treated groups, the load/deflection stress had statistically sagnificant difference except group 3 and group 4.(3) Different heat treatment have different effect on the long term change of the stainless steel archwire load/deflection stress.(4) The load/deflection stress of stainless steel archwire was statistically correlated with heat treatment temperature and time.Conclusions:(1) Heat treatment changes the load/deflection stress of stainless steel archwire.(2) Different heat treatment temperature and time result in different change of archwire characteristics.(3) Over heated stainless steel archwire will decrease the clinical expected function.(4) 0.018" stainless steel archwire heat treated by moderate temperature and 5-10s is suitable.(5) The heat treatment pattern should be selected properly for the clinic requirement.
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