Rationale of the segmented approach to orthodontic treatment.

Modern orthodontics requires defined treatment goals. To achieve them, known force systems must be used to control the active units (teeth being moved) and the reactive units (anchorage teeth). This article discusses the methods of controlling the force systems through the variables of spring design and anchorage selection. Continuous and segmented arch treatment are contrasted in their ability to achieve optimal and defined force systems with minimal side effects.