ABSTRACT
Extraction space closure is an integral part of orthodontic treatment which demands a thorough understanding of the biomechanics. In the pre-adjusted edgewise technique, retraction is achieved either with friction (sliding) or frictionless mechanics. In the former, the wire and position of the bracket are important factors in tooth movement but the simplicity of friction mechanics is offset by the binding between bracket and archwire. This slows tooth movement, compromises the delivery of desired force levels, causes anchor loss and may be associated with undesirable side effect such as uncontrolled tipping and deep bite. A review of frictionless mechanics in general and most commonly used loops in retraction has been highlighted in this article.