Load-Deflection Rates and Maximum Deflection of Orthodontic Appliances

Abstract

For purposes of clarity and organization, the subject matter was divided into four separate phases. Each phase is distinct in that it deals with a specific facet of orthodontic force application; however, all phases are similar in that they deal with a measurement of force values.

The first phase of the thesis deals with a measurement of load-deflection rates of various arch wire designs. These arch wire designs were in the form of vertical loops or helical torsion springs, i.e., a vertical loop in combination with one or more 360⁰ loops contained therein.

The load-deflection rate in grams of force per mm. of deflection along with the maximum deflection of each wire design is given in table form in the study. Stainless steel wires marketed by the Rocky Mountain and Unitek Companies were tested in the study along with a new type of alloy known as Elgiloy.

In the second phase of the thesis, load-deflection rates of 360⁰ loops were determined. Both single and double 360⁰ loops were determined. Both single and double 360⁰ loops were tested. The force was applied to the loops in three ways, i.e., to close the loops, to open the loops, and at right angles to loops. These various load-deflection rates were presented in graph form in the thesis.

In the third phase of the thesis, load-deflection rates of some commonly used orthodontic elastics were determined and represented in graph form. A considerable lack of uniformity in regard to wall thickness and diameter was found in a great number of these elastics.

In the fourth phase of the thesis, a method has been described to obtain effective torque in the anterior segment using round wire. It was found that as much as 360 grams of force can be obtained in this way with .016” wire and as much as 660 grams with .020” wire.