When closing a diastema, differential amounts of mesial movement of the centrals are often needed. In this instance, force is applied from both chain elastics and coil springs. An arch wire has been placed (from cuspid to cuspid) to act as a guide and keep the centrals from tipping. The initial length of coil spring-placed distal to the central is equal to the distance between the brackets, plus the width of the central bracket. This amount will typically move the tooth 1.5mm. Increasing the amount of coil spring distal to one central can move it faster than the other. To prevent root resorption, the teeth should not be moved faster than approximately 1mm per month. Because this is such an active appliance, the patient should be seen every two weeks. Note: To prevent unwanted movement of the cuspids, a lingual bonded 3-to-3 retainer can be placed to create an anchorage unit.