THE EFFECT OF FRICTION ON THE BENDING STIFFNESS OF ORTHODONTIC BEAMS - A THEORETICAL AND IN-VITRO STUDY

The purpose of this study was to investigate the effect of friction on the bending stiffness of orthodontic beams. A theoretical and experim ental model have been established where tensile and compressive forces are applied to an arch wire to simulate the effect of additional fric tion during activation and deactivation, respectively. The results sho w that tensile force increases wire stiffness, and that compressive fo rce increases flexibility. Thus more force will be needed during activ ation and more force will be lost during deactivation. The amount of f orce lost increases nearly linearly with increasing friction. During a ctivation, the percentage increase in force due to friction for a give n deflection is about equal to the loss of force due to friction durin g deactivation. Friction affects thin flexible wires more than heavy w ires. Careful ligation is recommended in the leveling phase to reduce the negative side effects of friction.