Date of Award
Master of Science (MS)
Objective: To quantify efficacies and discrepancies of Invisalign® treatment of anterior intrusions, anterior extrusions, and incisor, canine and premolar rotations with correlations to age, gender, tooth, attachment, interproximal reduction, number of aligners, treatment time, and start date. Methods: Initial, progress, and final iTero® scans of patients treated with Invisalign® in the graduate Marquette University Orthodontics Clinic (Milwaukee, WI) were retrieved along with corresponding ClinChecks® as .stl files. These three-dimensional files were superimposed for best-fit using SlicerCMF4-0 software. A total of 67 anterior intrusions ≥ 0.5 mm, 39 anterior extrusions ≥ 0.5 mm, and 98 incisor, canine and premolar rotations ≥ 5° were compared with actual outcomes via linear or angular measurement. Movement thresholds were based on Invisalign® defaults for the use of Optimized Attachments. This study was approved by the Institution Review Board under protocol HR-3520. Results: Mean efficacies were 39% for intrusions, 53% for extrusions, and 51% for rotations. Mean discrepancies were -0.45 mm for intrusions, -0.36 mm for extrusions, and -6.8° for rotations. No significant associations were found with gender, tooth, treatment time, or ClinCheck® approval date during this retrospective study spanning 2.5 years. Increasing age and number of trays were each associated with decreased performance of intrusion and rotation but not of extrusion. For rotations, Optimized Attachments specific to rotation had superior performance compared to Optimized Attachments not specified for rotation. For intrusions and extrusions, no associations between attachment and performance were found. Interproximal reduction was weakly associated with improved extrusion but had no association with intrusion or rotation outcomes. Planned extrusions and rotations had an equivalent chance of opposite-expression as over-expression. Planned intrusions could have opposite-expression (i.e. could extrude) but never over-expressed. Conclusion: Under current Invisalign® defaults, no teeth perform categorically better or worse for any studied movement. Optimized Attachments should be prioritized for rotations over intrusions and extrusions. Interproximal reduction should only be performed when needed and with caution. As Invisalign® is a technology that is constantly evolving, continued research is required to stay educated on the performance of the appliance. A prudent practitioner would plan compensations based on current shortcomings.