[Biomechanical principles of orthodontic movement of teeth with periodontal involvement].

The presence of a reduced periodontal attachment has three fundamental effects on orthodontic tooth movement: the diminished resorptive bone surface necessitates a reduction in the magnitude of force applied; the apical shift of the center of resistance requires an adaptation of the force systems used; (moment/force ratio); the limited anchorage quality of periodontally susceptible teeth has to be considered biomechanically. Orthodontic movement of teeth with reduced attachment therefore requires differented planning and application of force systems in order to avoid root resorption and further bone loss.