Main Article Content
Extraction space closure represents a fundamental stage in a considerable number of orthodontic treatments. With extraction as a method of gaining space, space closure becomes subsequently important. To obtain the desired result of closing spaces within the arch it was essential to control the amount of anterior retraction and molar protraction. There were different space closure measures advocated in the edgewise technique based on anchorage situations. The principles for retraction currently used can be described as either "frictional" system in which the canine, through application of a force, is expected to slide distally along and is guided by a continuous arch wire or frictionless system with forces and couples built into the loops of an arch section. In this review article some of the commonly used loops for closing extraction spaces by frictionless mechanics are explained.