Evaluation of skeletal stability after BSSRO in skeletal class III with anterior open bite

OR = 1mm). Serial lateral cephalometric radiographs were taken within 2 weeks preoperatively, within 1 week postoperatively and at a follow up period that ranged from 7 to 24 months postoperatively. All cephalometric radiographs were traced and digitized using the Quick ceph image Pro for analysis. And then, horizontal and vertical changes of reference points(B point, Pogonion, L1) were assessed by the linear measurements in millimeters on both axes. The results were as follows: 1. Mean horizontal relapses were 0.67+/-0.93mm (11%) at B point (P0.05). 3. The mean angular change of occlusal plane to SN was 0.24+/-1.19 (P>0.05) and that of mandibular plane to SN was 1.03+/-1.85 (P<0.05). 4. There was correlation between the extent of preoperative overbite and the postsurgical relapse at B point and Pogonion. 5. There was no correlation between the amount of surgically produced horizontal movement and the postoperative horizontal relapse at B point.

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

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 1000degreesF, but elongation was decreased. And the results were reversed above 1100degreesF. After heat treatment of the sample for 9 minutes at 1000degreesF, the maximum tensile strength and yield strength were 213.6kg/mm2, 140.1kg/mm2, respectively. Both tensile strength and yield strength were decreased progressively above 1100degreesF. Elongation was appeared the minimum value (8.6%) after heat treatment for 9 minutes and 12 minutes at 1000degreesF. 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 4.947microgram/cm2, 3.088microgram/cm2, respectively after heat treatment for 12 minutes at 1300degreesF. 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.