Award Date

May 2016

Degree Type


Degree Name

Master of Science (MS)


Dental Medicine

First Committee Member

James Mah

Second Committee Member

Brendan O'Toole

Third Committee Member

Bob Martin

Fourth Committee Member

Clifford Seran

Fifth Committee Member

Richard Walker

Number of Pages



Objective: To determine the optimal method to correct rotations of conical teeth using

thermoplastic appliances with and without attachments.

Introduction: Despite the increasing popularity of clear aligner therapy there are still questions as to its effectiveness, efficiency, case selection and limitations. It has been reported that the full prescription for clear aligners is not expressed, and that the mean accuracy of any type of tooth movement using clear aligners is only 41% (Drake, 2012). One of the major limitations of clear aligner therapy is correction of rotated conical teeth, especially canines and premolars (Kravitz, 2008). According to Simon, et al. (2014) mandibular premolar derotation has the lowest predictability of movement and accuracy with clear aligners. This is due to the fact that conical teeth lack interproximal undercuts, and as result the aligner tends to slip as derotation is attempted (Kravitz, 2008; Simon, 2014). Clear aligner manufacturers therefore recommend the use of resin bonded attachments, interproximal reduction, overcorrection, auxiliaries, or adjusting aligners with thermopliers in order to achieve derotation of conical teeth.

Materials and Methods: The design of this study is prospective and experimental. This

research will be a comparative study to examine the effect of attachment location and the number of attachments on rotational control of conical teeth. Rotational control without attachments or adjustments will be compared to rotational control with attachments, or with the use of a clear aligner adjusting plier (Hu-Friedy Vertical Rectangular Adjustment Plier). Total de-rotation will be recorded as an angular measurement after placement of each aligner, as measured on a digital scan (Ortho Insight 3D, Chattanooga, TN) using Geomagic Design software (3D Systems, Cary, NC).

Results: Results of a one-way ANOVA showed that there were no statistically significant

differences between 7 of the 9 groups. The group with a rectangular attachment on the buccal surface of tooth #29 had the highest overall observable rotational correction.

Conclusions: Attachments appear to improve rotational correction of the lower right second premolar. Increasing the number of attachments does not appear to aid rotational control, as the group with a single buccal attachment had the highest overall rotational correction. Multiple attachments, and adjusting aligners using the Hu-Friedy vertical rectangular adjusting plier on the lingual surface of the thermoformed aligner appear to impede rotational correction in this study.


clear aligners; clear aligner therapy



File Format


Degree Grantor

University of Nevada, Las Vegas




IN COPYRIGHT. For more information about this rights statement, please visit

Included in

Dentistry Commons