Award Date


Degree Type


Degree Name

Master of Science (MS)


Dental Medicine

First Committee Member

Tanya Al-Talib

Second Committee Member

Brian Chrzan

Third Committee Member

Robert Danforth

Fourth Committee Member

Amei Amei

Number of Pages



Objective: This study aimed to determine whether there are differences between pre-orthodontic treatment dimensions when compared to the virtual treatment simulations and actual orthodontic treatment outcomes in Class II malocclusions treated with two or four premolar extractions.

Introduction: The use of intraoral scanners has become commonplace in orthodontic practices, giving practitioners the ability to scan and assess maxillary and mandibular dental morphology and occlusal relationships chairside and in real-time. Practitioners can use virtual treatment planning to evaluate different extraction patterns, visualize potential non-extraction outcomes using interproximal reduction, and alter anchorage strategies based on the amount of retraction or protraction required for desired space closure. Similar to the dental Visualized Treatment Objective (VTO), digital treatment projections allow the clinician to both visualize and quantify the degree and direction of tooth movement desired.

Materials and Methods: 46 Class II division 1 patients were selected for this study: 22 subjects treated with two maxillary premolar extractions, 24 treated with four premolar extractions. Patients were selected based on presentation of Angle Class II malocclusion, confirmed with evaluation of digital study models. All digital treatment projections were constructed using uLab Systems (uLab Systems Inc. Redwood City, CA), and measurements for intermolar width, inter- canine width, overjet and overbite were recorded.

Results: Two-tailed paired T-tests were performed to determine if there was a significant difference between variables pre-treatment, post-treatment and from virtual setup with a significance level of P < 0.05. Group 1 treated with two premolar extractions resulted in a significant difference between maxillary intercanine width, mandibular intercanine width, and overbite between uLab virtual setup and treatment groups. Group 2 treated with four premolar extractions found significant differences between maxillary intermolar width, maxillary and mandibular intercanine widths, and overjet between treatment and virtual setup groups. There was a significant difference for all variables measured when comparing pre-treatment measurements to virtual setups treated with two premolar extractions. When comparing pre- treatment to virtual setups treated with four premolar extractions, there was a significant difference in all variables except overbite. Comparison of pre-treatment to post-treatment values treated with two premolar extractions found significant difference between maxillary and mandibular intermolar width, maxillary intercanine width, overjet and overbite. There was a significant difference between pre- and post-treatment in maxillary intermolar width, mandibular intermolar width, and overjet treated with four extractions.

Conclusions: Despite statistically significant differences between treatment outcomes and virtual setups in variables including overbite and overjet, the difference between them was not clinically significant. Statistically significant differences in both the maxillary and mandibular intercanine widths between digital setups and treatment outcomes suggests that with software simulations, the clinician tends to over-expand the intercanine width. Similarly, virtual setups showed a tendency to expand intercanine dimensions more than actual treatment outcomes when comparing to initial pre-treatment dimensions. This study supports the use of virtual setups for the purpose of guiding treatment and visualizing potential outcomes.


Class II; Extraction; Intraoral Scanner



File Format


File Size

3.2 MB

Degree Grantor

University of Nevada, Las Vegas




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