Award Date


Degree Type


Degree Name

Master of Science (MS)


Dental Medicine

First Committee Member

James Mah

Second Committee Member

Tanya Al-Talib

Third Committee Member

Brian Chrzan

Fourth Committee Member

Pouya Momtaz

Fifth Committee Member

Courtney Coughenour

Number of Pages



Background: Clear Aligner Therapy (CAT) is regarded as a popular esthetic alternative to conventional orthodontic treatment with fixed labial appliances. The mechanism of action, force delivery and limitation of this treatment modality remain largely unknown despite its popularity, the high demand and the relatively long evolutionary track of clear aligners. There are only few studies that addressed the elements that influence the efficiency of clear aligners, namely, the attachment design and aligner materials. It is widely believed that clear aligners are not suitable for extraction cases due to their lack of control over the root movement.

Objectives: This in vitro simulation examines the efficiency of clear aligners with bodily tooth movement when variable attachment designs and aligner materials are used.

Materials and Methods: 3D printed resin typodonts with extracted first premolar were used to simulate the maxillary right canine distal bodily movement in a wax medium with sets of 10 clear aligners. Three types of resin attachments, a vertical rectangular, a multiplanar, and a twin attachment, were bonded to the facial surface of the canine. Three types of aligner materials, two Glycol-modified Polyethylene Terephthalate (PET-G) and one Copolyester-Polyester multi- laminate composite were used to fabricate the aligners. The canine crown movement, root movement and long axis changes were measured after the simulations, and the data were analyzed using one-way Analysis of Variance (ANOVA).

Results: Statistically significant differences were found between the 12 treatment groups. The highest amount of linear crown movement and distal tipping of the canine was observed in the (No Attachment Groups), while the (Twin Attachment Groups) showed the highest linear root movement and the highest ratios of bodily movement. No statistically significant differences were observed between the treatment simulation groups based on aligner materials.

Conclusions: The majority of the canine movement was the result of tipping. However, the presence of resin attachments, especially the twin attachment, reduced the distal tipping and improved the aligners’ control over force delivery to the coronal and root portion of the canine. Despite the significant differences identified between the attachment groups, there was no clinical evidence to support that a specific attachment design would have a significant impact on treatment outcome, or the intraoral behavior of the clear aligners. No significant differences were found between the thermoplastic materials tested in this study with respect to the overall distal tipping, root movement and the ratio of bodily movement of the canine.


Aligners; Attachment; Invisalign; Malocclusion; Orthodontics; Thermoplastics


Biology | Biomechanics | Dentistry

File Format


File Size

3300 KB

Degree Grantor

University of Nevada, Las Vegas




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Available for download on Thursday, May 15, 2025