Methods: Unitek® 18/8 0.51mm diameter round stainless steel orthodontic wire was used to bend ten buccal retractors with traditional coils (3.2mm outside diameter) by hand using loop-forming pliers. Five were formed by bending the coils through approximately 315º, taken as the traditional form, and five retractors were formed by over-bending the coils deliberately by approximately 45º (with the legs crossing), and then re-bending to the traditional position. The LDR’s of the retractors were established (at room temperature) at 14, 16, 18 and 20mm retractor lengths on a gravity scale device. A further six retractors were formed, three normally and three by over- and re-bending and heat-treated to 350º C for 25 minutes. CorelDRAW was used to measure before and after heat-treatment angles. Statistical analysis was performed.
Results: The mean LDR of the over- and re-bent retractors was significantly less than the mean LDR of the traditional retractors (P≤0.05). After heat treatment the over- and re-bent retractors opened significantly less than the traditional retractors (P≤0.05).
Conclusion: Over-bending by some 45º and then re-bending supported buccal retractors improves their performance by employing both facets of the Bauschinger effect to their advantage. It is recommended that supported buccal retractors be formed in the manner introduced above.