Orthodontic anchorage is defined as resistance to unwanted tooth movement. During orthodontic treatment the teeth are exposed to forces and moments, and these acting forces always generate reciprocal forces of the same magnitude but opposite in direction. To avoid unwanted tooth movements and maintain treatment success, these reciprocal forces must be diverted. Orthodontic anchorage, defined as the ability to resist these unwanted reactive tooth movements, can be provided by other teeth, by the palate, head, or neck, or implants in bone. The goal is to maximize desired tooth movement and minimize undesirable effects. This book covers each part of orthodontic anchorage in detail.