Efficacy of planned moderate to severe torque changes in mandibular central incisors with an initial series of Invisalign aligners: a retrospective cohort study.

Objectives: To determine whether the achieved mandibular central incisor lingual root torque (LRT) changes matched the planned changes after treatment with an initial series of Invisalign aligners when ≥10° of torque change was planned.

Materials and methods: A sample of adult patients who underwent treatment with the Invisalign appliance between 2013 and 2021 were evaluated. The pretreatment, planned, and achieved posttreatment digital models were measured using Geomagic Control X metrology software. The effect of age, number of prescribed aligners, sex, the presence of power ridges (PRs), and differing weekly wear protocols (WPs) in relation to the achieved LRT changes were determined.

Results: Seventy mandibular central incisors from 35 patients satisfied inclusion criteria. The accuracy of the achieved lower incisor LRT compared with that planned was 58.2%. Underexpression of planned torque changes was observed in most incisors (N = 66; 94.3%), with a clinically significant shortfall (≥5°) observed in 68.6% (N = 42) teeth. Patient age, sex, the WP, or the presence of PRs did not influence the differences between planned and achieved outcomes (P > .05). The prescribed number of aligners was influential in the difference between the planned and achieved torque outcomes (P < .01).

Conclusions: Underexpression of mandibular central incisor root torque was observed in most incisors in patients when ≥10° change in LRT was planned. Lower incisor LRT was not significantly affected by the presence of PRs or differences in WPs.