Efficacy of planned root torque changes of instanding maxillary lateral incisors with the Invisalign appliance

This study aimed to examine the efficacy of planned root torque changes of instanding maxillary lateral incisors (IMLIs) in patients treated with an initial series of Invisalign aligners (Align Technology, Santa Clara, Calif).

Pretreatment digital models and digital models representing the planned and achieved treatment outcomes of adult patients prescribed an initial series of Invisalign aligners were measured using Geomagic Control X (version 2017.0.3; 3D systems, Rock Hill, NC). The type of orthodontic tooth movement (OTM) that was planned and achieved was assessed using the center of rotation as a reference point.

A sample of 65 patients with 95 IMLIs satisfied the inclusion criteria. The mean accuracy of the planned root torque change of the IMLIs was 78.9%. Palatal root torque was planned for most (82.1%) IMLIs. The accuracy of root torque expression differed according to whether planned changes were in a palatal or labial direction. Planned palatal torque changes showed a higher level of accuracy. Linear regression analysis indicated that age, sex, presence of an attachment, and type of attachment did not influence the accuracy of root torque expression (P >0.05), whereas planned anteroposterior movement of the IMLI crown did (P <0.01). The most frequently achieved OTM was uncontrolled tipping (54.7%).

The achieved root torque in IMLIs with an initial series of Invisalign differed significantly from that planned. The amount of anteroposterior movement was significantly related to the efficacy in achieving the planned root torque.