When there is not sufficient space for all teeth to erupt into their ideal position, it is important to determine the cause for this deficiency. As shown, arch length is less than ideal because due to early loss of primary molars and cuspids. The first molars and bicuspids erupted mesially. To regain space for the cuspids, the posterior segments need to be moved back to their normal position. This sagittal design uses two screws with the cut in the acrylic ( just mesial to the first bicuspids) to regain the lost space. As the space is regained, cuspid retraction springs are used to guide the cuspids into position. Note: second molars are not present. Once they have erupted, distalization of the posterior segments becomes very difficult with this design. Therefore, when your evaluation indicates that the arch length needs to be gained in a distal direction, second molar removal should be part of your treatment plan. By the nature of the appliance design, some reciprocal movement of the anteriors will always still occur.