Date of Award

Summer 2019

Document Type


Degree Name

Master of Science (MS)



First Advisor

Ahuja, Bhoomika

Second Advisor

Liu, Dawei

Third Advisor

Nimeri, Ghada


Objective: To compare the efficacy of Invisalign’s (Align Technology, Inc., Santa Clara, CA) optimized and conventional attachments on rotational and extrusive tooth movements.Materials and Methods: Initial, predicted, and achieved digital dental models from 100 orthodontic patients were exported from Invisalign’s ClinCheck software as stereolithography (STL) files and subsequently imported into the Slicer CMF program (open source, version 4.7.0) for superimpositions on posterior teeth with no planned movement. Rotational and extrusive measurements for both optimized and conventional attachment types were made on 382 teeth from the superimposition of the initial and predicted models (“predicted movement”) and from the superimposed initial and achieved models (“achieved movement”). Predicted and achieved movements were compared using paired t-tests. Independent t-tests were used to compare tooth movements for optimized versus conventional attachments. One-way ANOVAs were used to compare accuracies by tooth type. Data analysis was performed at the PResults: Mean differences between predicted and achieved movements were of high statistical significance for all attachment types and tooth movements. For extrusion, this mean difference was also clinically significant (0.40 mm and 0.62 mm for optimized and conventional attachments, respectively). Overall mean accuracy was 57.2%. Mean accuracy was 63.2% for rotation and 47.6% for extrusion. The most accurate tooth movement was extrusion of the maxillary central incisor with a conventional attachment (75.9%) and the least accurate was extrusion of the mandibular canine with a conventional attachment (16.1%). These differences were statistically significant. There was no significant difference in accuracy between tooth types for rotation. Interproximal reduction (IPR) or spacing did not significantly affect accuracy. Differences between accuracies of tooth movements using optimized versus conventional attachments for both rotation and extrusion were neither statistically nor clinically significant.Conclusion: Conventional attachment types may be just as effective as Invisalign’s proprietary optimized attachments for rotations of canines and premolars, and for extrusion of incisors and canines. Clinicians should consider overcorrection or mid-course correction, especially for extrusion of anterior teeth. A larger sample size of teeth with IPR or spacing is needed to draw more definitive conclusions about how these conditions affect the accuracy of tooth movements.

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