Abnormal occlusal forces, periodontal disease and poor restorative work can cause interproximal spacing to occur in the posterior segments. This often leads to food impaction that is not only annoying, but can also contribute to a worsening of the periodontal condition. This excess space can be easily reversed (shown here). Anchorage is the key to successfully closing this space. The appliance typically requires anterior retention using a combination of bilateral clasping and a labial bow Then, stainless "retraction" screws are placed bilaterally as needed to close the interproximal spaces through mesial movement of molars. Typically, heavy "C" Clasps are placed around the distal of the last molars and the acrylic is removed from the interproximal areas around the teeth needing mesial movement.