열처리한 교정용 호선의 기계적 성질과 금속유리에 대한 연구

The effects of heat treatment on mechanical properties and metal release from heat-treated orthodontic archwires

The purpose of this study was to evaluate the effects of heat treatment on mechanical properties in 0.016″ x 0.022″ blue Elgiloy wires and to measure the amounts of nickel and chromium released from the wires in artificial saliva. Ultimate tensile strength, yield strength and elongation were measured with universal testing machine (Instron). and the amounts of nickel and chromium released from the sample were measured with atomic absorption spectrophotometer after one week immersion in the artificial saliva. Ultimate tensile strength and yield strength were progressively increased below 1000°F, but elongation was decreased. And the results were reversed above 1100°F. After heat treatment of the sample for 9 minutes at 1000°F, the maximum tensile strength and yield strength were 213.6kg/mm^², 140.1kg/mm^², respectively. Both tensile strength and yield strength were decreased progressively above 1100°F. Elongation was appeared the minimum value (8.6%) after heat treatment for 9 minutes and 12 minutes at 1000°F. There was a pronounced increase in nickel and chromium liberation with increasing time and temperature. The maximum amounts of nickel and chromium released form the sample were 4.947µg/cm^², 3.088µg/cm^², respectively after heat treatment for 12 minutes at 1300°F. Heat treatment is applied to orthodontic wires, especially cobalt-chromium alloys, for the purpose of stress-relievning and hardening. When the heat-treatment of orthodontic wires, the heating procedure should be well controlled in order to have no effect on corrosion resistance and mechanical properties.