3 Low Friction — Poor Control (Undersized Archwire) High Friction — Full Control (Full Sized Archwire) SPEED — THE NEW PARADIGM EDWARD ANGLE’S EDGEWISE APPLIANCE With its introduction almost a century ago, Edward Angle’s edgewise appliance represented the culmination of years of work and many variations in appliance design. Testimony to his genius lies in the striking similarity of his original design to modern orthodontic appliances, in spite of the incorporation of significant improvements. Improvements such as direct bonding and a reduced need for archwire bends have contributed to increased clinical and treatment efficiencies while improving patient acceptance. However, reliance on a refinement of an original design, possesses inherent limitations. GOALS IN APPLIANCE DESIGN An appliance design which provides a truly efficient means of achieving treatment objectives demands more than simply certain built-in features. This is only the starting point. A truly efficient orthodontic appliance must provide predictability and control. It must enhance, and not inhibit, treatment progress. It must maximize clinical efficiency, while simplifying treatment modalities. It must be aesthetically pleasing, while providing ease of hygiene. And, it must be safe for patient, clinician and staff. Twin edgewise appliance design has fallen short of this ideal. THE TWIN EDGEWISE APPLIANCE The twin edgewise bracket is a passive appliance, generic in design. Unable to independently affect and control tooth movement, it relies on a ligature to secure it to the archwire. Together they are wholly dependent on the archwire for their control. The inherent limitations imposed by this bracket - ligature - archwire relationship ultimately compromise the treatment and clinical efficiency of the appliance. Conventional “tie-wing” appliances have found themselves designed into an uncomfortable corner. Their dependency on biodegradable elastomeric ligatures and full sized wires for control comes at the price of predictability and clinical efficiency. Only with full-sized wires do these elastomeric ligatures maximize their limited control and that control diminishes with time. Their frictional properties tend to inhibit treatment progress in an unpredictable manner; reducing this frictional burden through the utilization of undersized wires sacrifices control. In addition, the degeneration and unhygienic nature of elastomerics require that they be continuously maintained, thereby compromising clinical efficiency.
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