[The Burstone technic: extremely light forces and pressures]

During orthodontic displacement, integrity of root and periodontis needs the knowledge of forces systems developed by orthodontic appliances. Analyses of different tooth movement require some biomechanic rules especially to choose magnitude and direction of forces, with respect to the center of resistance and the C/F ratio. Forces systems developed by the Burstone segmented arch technique have to be shown biologic because they produce light and variable pressures according to patient age and rate of periodontal disease.