The basics of orthodontic mechanics

Abstract The biologic cascade of events that ultimately results in bone remodeling and orthodontic tooth movement begins with the mechanical activation of an orthodontic appliance. The force systems produced by orthodontic appliances, consisting of both forces and moments, displace teeth in a manner that is both predictable and controllable. By varying the ratio of moment to force applied to teeth, the type of tooth movement experienced can be regulated by the orthodontist. Orthodontic appliances obey the laws of physics and can be activated to generate the desired force systems to achieve predetermined treatment goals for individual patients. Likewise, any orthodontic appliance can be analyzed to define the mechanical force systems it produces. Understanding the biomechanical principles underlying orthodontic appliance activations is essential for executing efficient and successful orthodontic treatment.