SELF LIGATION www.speedsystem.com What are Active Self-Ligating Brackets? 3 Active self-ligating brackets contain a flexible, moveable component which entraps the archwire. This flexible component can also cooperate with the archwire in precise corrective tooth movement. Active self-ligating brackets offer the dual advantage of low friction and precise control. Low friction is ensured by the "metal to metal" contact between the bracket components and the archwire. It can be argued that friction is minimized further with initial undersized wires. Undersized archwires are free to migrate either mesially or distally within the slot during initial alignment. Later in treatment, when larger sized wires are used, the elasticity possessed by the flexible component ensures that contact points are constantly "freed up" thereby minimizing frictional binding during tooth translation. Precise control in all three planes of space is ensured by the unique interaction between the archwire and the active component of the bracket. Active self-ligating brackets possess the unique ability to re-orient themselves and their accompanying tooth relative to the archwire when corrective tooth movement is required. Active self-ligating brackets employ a flexible component to entrap the archwire. Passive self-ligating brackets employ a rigid component to entrap the archwire. Active self-ligating brackets can cooperate with the archwire in corrective tooth movement. Passive self-ligating brackets are limited in their tooth control by the difference in size between the archwire and the archwire slot. What are Passive Self-Ligating Brackets? Passive self-ligating brackets contain a rigid moveable component which simply entraps the archwire. Passive self-ligating brackets are not new and early designs include the Boyd (1933), Ford (1933), Edgelok (1972), Mobil Lock (1980), Activa (1986) etc. None of these designs enjoyed clinical or commercial success due to their limited tooth control and bulky design. Modern passive self-ligating bracket designs are subject to the same design, and therefore performance constraints, as earlier models. Tooth control is ultimately determined by the difference in dimensions between archwire and archwire slot. This results in a "race to fill the slot" which can result in the application of excessive clinical forces, especially upon archwire engagement. Even with so called "full sized wires" tooth control is limited as an archwire can never completely fill the archwire slot. Passive self-ligating brackets offer reduced friction, as do active self-ligating brackets, mainly through the elimination of elastomeric ligatures. It is questionable though whether the passive design differs significantly from the active design from a frictional standpoint in the clinical environment. Clinicians who have utilized both designs report no noticeable difference in the forces required to translate teeth along a given archwire.
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