Friction in orthodontics

Friction is the force that resists against the movement of one surface in relation to another and that acts on the opposite direction of the desired movement. Tooth movement is determined by the total forces applied on the teeth. This includes forces from the appliance and muscular forces that are produced during function. In addition, frictional forces can operate that can considerably alter the force system. Friction force is produced by many possible appliance activations like buccal, lingual, apical, and occlusal forces. Friction force is also produced by moments acting on the archwire by ¿tip¿ or ¿torque.¿ The ligation mechanism produces normal forces adding to the friction force. The ligation is used to engage the archwire in the bracket. Any additional ligation force will add to the friction force and usually is not desired.