Bracket slot size and torque control

To obtain effective torque control, three options are available:

1.  "Fill up" the bracket slot. In a 0.022-inch slot, the logical archwire is a 0.021 x 0.025-inch archwire, which would provide the same torque control as a 0.017 X 0.025-inch archwire in a 0.018-inch slot.

2.  Place certain torque in the archwire.

3.  Place certain torque in the bracket slot.

It should be understood that for every 0.001 inch of freedom between the archwire and the vertical bracket slot, approximately 5 degrees of effective torque is lost. This means that if the final archwire is a 0.019 x 0.025-inch archwire in a 0.022-inch slot, 15 degrees of torque is lost. A 0.017 X 0.025-inch archwire in a 0.018-inch slot would create a loss of 5 degrees.

The 0.018-inch slot dimension was selected over the 0.022-inch slot dimension for three reasons: better torque control, better leveling mechanics, and patient comfort. First, accurate torque control for the maxillary and mandibular anterior teeth is achieved by finishing each case with a 0.017 X 0.025-inch stainless steel archwire, which results in nearly complete engagement of the bracket slot to the archwire. Eliminating the 5 degrees of freedom from the bracket's torque value results in more effective transmission of torque to the tooth. Second, the additional interbracket space (discussed later) allows stiffer archwires with accentuated curves to be placed earlier in treatment. The result is more efficient leveling mechanics. Third, the patient's discomfort is reduced by use of the smaller archwires in the 0.018-inch slot bracket with greater interbracket space.

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  • Category: Dental disease