The Slop-Py Side Of Orthodontics

Dr. and Anna Razdolsky are happy to share that their daughter, Dr. Elizabeth recently co-authored a continuing education article on a novel way to calculate the necessary force required for different archwires during orthodontic treatment. Published in Orthotown, the written course titled, “Slop-py Work – Calculating theoretical torque loss utilizing rectangular and square-shaped archwires” shares the team’s research and formula.

“Overall, because appliances such as braces have rectangular slots, they can utilize rectangular archwires to control torque expression. However, a higher degree of dimensional precision of brackets and archwires is required to take both torque expression and the wire/slot play into account,” the authors write. “Torque must be adjusted in a controlled manner, so the resulting force does not prevent any biological tooth movements; therefore, for desirable physiologic forces to be applied, it’s necessary to take into account a certain degree of slop between the wire and bracket interface. However, few effective formulas exist that provide information to assist with clinical decisions,” they continue.

Fixed orthodontic appliances are designed to apply force to teeth in three planes of space. The first order is lingual and rotational movements; second order is gingival and root tip; and third is the rotation along a mesial–distal axis, or torque. It is in this third order where fixed orthodontic appliances accommodate a rectangular archwire that controls third-order movements.

If rectangular wires are too snug to brackets the force may hinder biological tooth movement, therefore some play or “slop” between the wire/bracket interface is necessary allowing a reduced expression of torque to create a more physiological application of force during tooth movement.

“To select the ideal archwire for a given bracket system, it is beneficial to understand the relative degrees of slop between different archwire dimensions within a given bracket system. Although this can be calculated mathematically, it is important to note that calculated theoretical slop does not take into account archwire stiffness due to its material and geometrical properties and variation within the manufacturing process,” the authors write.

It is because this slop between varying archwire options is of critical clinical significance, the authors developed the continuing education study to inform readers of the simple formula to mathematically calculate it.

To read more on Elizabeth and her team’s continuing education course read Orthotown’s December 2020 issue at