Effect of Gingival Margin Design on Clear Aligner Material Strain and Force Delivery

Abstract

Aim: To evaluate the effect of the gingival margin design on strain distribution and forces and moments delivered from Essix ACE and Zendura FLX to a maxillary central incisor during labial tipping about a simulated center of rotation.Methods: Clear aligners (CAs) were prepared from two materials, Essix ACE and Zendura FLX, in 0.030 mil (0.75 mm) thickness. For each material, three margin designs—scalloped, straight cut 0.75 mm above gingival zenith and straight cut 1.5 mm above gingival zenith—were fabricated with no tooth movement and 2.4 degrees of labial tipping about a simulated center of rotation, for a total of 12 designs. Three CAs were manufactured for each of the 12 designs, for a total of 36 aligners. Forces and moments were recorded with a force measuring device in all six degrees of freedom, from the center of the crown and the center of resistance (COR).