Clinical expression of programmed rotation and uprighting of bilateral winged maxillary central incisors with the Invisalign appliance: A retrospective study

Introduction: Winged maxillary central incisors (WMCI), defined as mesiopalatal rotation of the crowns of maxillary central incisors, is a common dental trait that affects smile esthetics. This retrospective study aimed to determine the efficacy of rotation and uprighting tooth movements of bilateral WMCI with Invisalign (Align Technology, Santa Clara, Calif).

Methods: Initial, predicted, and achieved stereolithography files of 30 adult patients, consecutively treated with the Invisalign SmartTrack appliance, were superimposed using Geomagic Control X 64 (3D Systems, Rock Hill, SC). The pairs of incisors were assessed for rotation using the interlabial angle (ILA), and individual incisors were measured for rotation and tip.

Results: Programmed rotation and uprighting of WMCI are mostly undercorrected with the Invisalign appliance. The mean shortfall in ILA was 10.5° (standard deviation [SD], 10.66; 95% confidence interval [CI], 5.89-14.19; P <0.001) for a mean predicted change of 35.27°. For individual incisors, a mean shortfall of 5.38° (SD, 5.88; 95% CI, 3.58-6.76; P <0.001) was found for a mean 18.75° predicted change in rotation. A mean predicted change in tip of 7.06° showed a mean shortfall of was 2.16° (SD, 3.86°; 95% CI, 1.03-3.01; P <0.001). A moderate and statistically significant correlation between shortfalls in rotation and tip was observed (r = 0.44). Linear regression analysis was used to formulate an equation as a clinical tool to determine the likely achieved outcome on the basis of the predicted change.

Conclusions: Predicted changes in rotation, ILA, and tip were both under and overexpressed. In particular, tip was dependent on the magnitude of planned change. The random inconsistencies in the clinical expression of rotation and tipping warrant careful monitoring and/or remedial actions such as overcorrections aligners.