COMPARISION OF MAXILLARY ANTERIOR TOOTH MOVEMENT BETWEEN INVISALIGN AND FIXED APPLIANCES

Shaun J. Murphy, Sanghee Lee, Joshua C. Scharm, Stella Kim, Aya A. Amin, Tai-Hsien Wu, Wei-En Lu, Ai Ni, Ching-Chang Ko, Henry W. Fields, Toru Deguchi

What did the authors aim to do in this study?

The aim of this research project was to compare the amount of maxillary incisors and canine movement between Invisalign and fixed orthodontic appliances using artificial intelligence and identify any limitations of Invisalign.

How did the authors evaluate?

For this study, a sample of sixty patients were selected randomly [Invisalign (n = 30); Braces (n = 30)] and the Peer Assessment Rating (PAR) analysis was used to indicate the severity of the patients in both the groups. Pre-treatment and post-treatment digital models of the maxillary arch were acquired from iTero or 3-shape intraoral scanners. The models were coded to provide anonymity. Treatment models were then superimposed using Geomagic Design X software (3D Systems ©, Rock Hill, SC). Pre- and post-treatment models were superimposed utilizing palatal rugae points for the plane of reference. Digital color-mapping illustrated whether the scans were accurately superimposed. Blue and red color-mapping (calculated based on an in-house VTK program) also portrayed a difference in tooth position between the pre- and post-treatment digital models, validating movement of the tooth from before to after orthodontic treatment (Figure 1). After collecting accurate superimpositions of pre- and post-treatment models, individual teeth were segmented (Figure 2A) and specific landmarks were identified, respectively, by an artificial intelligence system, called Two-Stage Mesh Deep Learning (TS-MDL) (Figure 2B).

Tooth movement between pre- and post-treatment was calculated based on 6-degrees of freedom. This included: mesial-distal translation, buccal-lingual translation, extrusion/intrusion, tipping (or mesiodistal angulation), rotation, and crown torque. Incisor and canine movement in the six directions was then analyzed to a significance level of α=0.05.

Linear mixed effect model was used to compare the two treatment groups in both overall tooth movement.

What did the authors find?

Based on the post-treatment Peer Assessment Rating scores, quality of finished patients in both groups were similar. In maxillary incisors and canines, there was a significant difference in movement between Invisalign and conventional appliances for all 6 movement directions. The greatest differences were with rotation and tipping of the maxillary canine, along with incisor and canine torque. The smallest statistical differences were observed for incisors and canines were crown translational tooth movement in the mesiodistal and buccolingual directions.

What did the authors conclude?

• In this study, differences in tooth movement were found between Invisalign and fixed orthodontic appliances, especially incisor and canine torque, rotation and mesiodistal tipping.

• Invisalign is still an effective and appreciable treatment option for patients.

• It is important to acknowledge that, tooth movements which may pose treatment challenges and recognize those cases which may be more successfully treated using fixed orthodontic appliances.

Shaun J. Murphy, Sanghee Lee, Joshua C. Scharm, Stella Kim, Aya A. Amin, Tai-Hsien Wu, Wei-En Lu, Ai Ni, Ching-Chang Ko, Henry W. Fields, Toru Deguchi, Comparison of maxillary anterior tooth movement between Invisalign and fixed appliances, American Journal of Orthodontics and Dentofacial Orthopedics, Volume 164, Issue 1, 2023, Pg 24-33.