不同热处理后不锈钢摇椅弓的加、卸载应力及其力学性能的实验研究

目的研究不同热处理不锈钢摇椅弓的加、卸载应力及其力学性能。方法①将12 cm0.018-inch的不锈钢圆丝弯制成4 mm深度的摇椅弓,进行不同温度、时间的热处理。②不锈钢摇椅弓根据不同的热处理情况分为6组：热处理1、2、3、4、5组和未经热处理的对照组,每组50个样本。③用万能材料力学实验机测试各组摇椅弓加、卸载应力值。④在观察1、2、3、4周后分别测试各组不锈钢摇椅弓的加、卸载应力变化情况。结果热处理1、2、3、4、5组和对照组摇椅弓丝的加、卸载应力-应变均呈近似的线性关系,无明显的平台期。热处理2、3、4、5组初始加、卸载应力值与对照组比较差异均有统计学意义（均P〈0.05）,保持后3、4周加、卸载应力值与对照组比较差异均有统计学意义（均P〈0.05）;热处理1组初始加、卸载应力值与对照组比较差异均无统计学意义（均P〉0.05）,保持后1、2、3、4周加、卸载应力值与对照组比较差异均无统计学意义（均P〉0.05）。保持4周后,各组不锈钢摇椅弓的加、卸载应力值均有所减小,热处理2、3、4组的减小程度均低于热处理1组和对照组（均P〈0.05）,热处理5组的减小程度高于对照组（P〈0.05）。经过热处理的不锈钢摇椅弓加卸、载应力与热处理温度200～400℃均呈正相关（r=0.871、0.855,均P〈0.05）。结论对于0.018-inch的不锈钢摇椅弓,在临床上进行热处理温度在200～400℃为宜,可使弓丝刚度增加。

Experiment Study of the Load Stress,Deflection Stress and the Mechanics of Capability of Stainless Steel Reverse-curve Archwire after Different Heat Treatment

Objective To study the load stress,deflection stress and the mechanics of capability of stainless steel reverse-curve archwire after different heat treatment.Methods ①12 cm 0.018-inch stainless steel wires were formed to 4mm reverse-curve archwires,and heat treated in different temperature and time.②Stainless steel reverse-curve archwires were set to 6 groups according to different heat treatment：the heat treatment group 1,2,3,4,5 and the control group without heat treatment,each group contained 50 samples.③The load stress,deflection stress of stainless steel reverse-curve archwires in each group were evaluated by Instron appliance.④After 1,2,3,4 weeks observation,evaluated the changes of the load stress,deflection stress of stainless steel reverse-curve archwires in each group.Results In the heat treatment group 1,2,3,4,5 and the control group,the load stress,deflection stress of stainless steel reverse-curve archwires are approximately linear,without apparent plateau.The initial load stress,deflection stress of stainless steel reverse-curve archwires of the heat treatment group 2,3,4,5 compared to the control group,the changes are statistically significant（all P0.05）,the load stress,deflection stress after 3,4 weeks observation compared to the control group,the changes are statistically significant（all P0.05）;The initial load stress,deflection stress of stainless steel reverse-curve archwires of the heat treatment group 1 compared to the control group,the changes are statistically insignificant（P0.05）,the load stress,deflection stress after 1,2,3,4 weeks observation compared to the control group,the changes are statistically insignificant（all P0.05）.After 4 weeks retaintion,load stress,deflection stress of stainless steel reverse-curve archwires in each group decrease,the heat treatment group 2,3,4 decrease less than the heat treatment group 1 and the control group（all P0.05）,and the heat treatment group 5 decrease more than the control group（P0.05）.The load stress,deflection stress of heat treated stainless steel reverse-curve archwires have the positive correlation with heat treatment temperature between 200 to 400 ℃（r=0.871,0.855,all P0.05）.Conclusion To 0.018-inch stainless steel reverse-curve archwire,the proper heat treatment temperature in clinic is between 200 to 400 ℃,which makes the hardness of archwire increase.