Intra-arch irregularities can be corrected using wire of low stiffness, wires of increasing stiffness, or by the activation of loops built into appliance. While the orthodontist controls only the magnitude of force when leveling with continuous arches, the configuration and position of loops offer the possibility of controlling the type and direction of force. In the present article the rectangular (R) loop was used for correction of first order irregularities, buccolingual movements, and rotation along the long axis of the tooth. The rectangular loops were capable of generating any desired moment to force ratio.
