Retraction Biomechanics in Extraction cases using Aligners

Retraction biomechanics in extraction cases using aligners focuses on controlled space closure after premolar extraction while maintaining anchorage, torque, and vertical control. Because aligners rely on intermittent forces and limited attachments, retraction is typically staged and programmed digitally, with anterior teeth often moved first or en masse depending on anchorage demands. Optimized attachments, power ridges, and aligner sequencing are used to control incisor torque and prevent tipping, while posterior anchorage is reinforced through attachments, sequential distalisation, or adjuncts such as elastics or temporary anchorage devices (TADs). Space closure is generally achieved through bodily movement rather than uncontrolled tipping by incorporating root control in the treatment plan, though refinements are commonly needed. Overall, successful retraction with aligners requires precise planning, patient compliance, and biomechanical considerations to approximate the force systems achievable with fixed appliances.