Defense Date


Document Type


Degree Name

Master of Science in Dentistry



First Advisor

Dr. Bhavna Shroff, D.D.S., M.Dent.Sc., M.P.A.

Second Advisor

Dr. Caroline K. Carrico, Ph.D.

Third Advisor

Dr. Steven J. Lindauer, D.M.D., M.D.Sc.


Purpose: To assess the perceived efficacy of aligners (Invisalign, Align Technology Inc) at performing extrusive movements of maxillary lateral incisors, determine a general threshold of when a maxillary lateral incisor is not extruding as predicted and requiring intervention, evaluate the frequency and methods of intervention to achieve the predicted extrusion, and to evaluate any related differences between orthodontists and general dentists, and between clinicians having treated various numbers of patients with Invisalign in the past 12 months.

Methods: An original 18-question survey was sent by mail to a randomized and geographically proportionate selection of orthodontic specialists (N = 400) and general dentists (N = 400) who were listed as providers on the Invisalign website. The data were analyzed using ANOVA and chi-square tests.

Results: 126 providers responded to the survey (15.8% response rate), including 36 general dentists and 90 orthodontists. Overall, the average perceived efficacy was 4.71 out of 10 (95% CI: 4.28-5.14). The threshold for determination of tracking issues was significantly associated with provider type, with orthodontists more often using 0.5mm as their threshold compared to general dentists (p=0.0305). General dentists were significantly more likely to prefer an optimized attachment (p=0.0001), whereas orthodontists were significantly more likely to prefer a gingivally beveled horizontal rectangular attachment (p

Conclusions: Average perceived efficacy for extruding maxillary lateral incisors with aligners was 4.71 out of 10. Orthodontists had a lower tolerance than general dentists for tracking issues (0.5 mm vs 1.0 mm, respectively). Refinement scan was the most common method of intervention. General dentists and orthodontists differed in their treatment planning preferences and timing of intervention.


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