Class ii malocclusion correction with invisalign: is it possible?

The governing concept for clear aligners arose in the midst of the U.S.’s recuperation from their second industrial revolution when rapid scientific recovery, standardization, and mass production found common ground in the American civilization. Clear aligners, in the beginning, looked like rubber tooth positioner appliances that were used in successive series for incremental tooth movements. It wasn’t until the 1960s that Nahoum introduced the first clear thermoplastic appliance capable of orthodontic tooth movement, and ever since then, advances in clear aligner technology have only seen an upward movement.

Through the progression of this technology and the sequential staging of tooth movements enough to generate orthodontic forces, Align Technology launched the Invisalign® system – a commercial success today. At first, Invisalign® aligners were only assigned for treatments that involved mild to moderate occlusal discrepancies. However, owing to the evolution of thermoplastic materials, a better comprehension of applied biomechanics, and the development of accommodating auxiliaries, Invisalign can now be used to treat a wider variety of complex cases including Class II.

Having said that, there are still unanswered questions regarding the efficacy of Invisalign for Class II malocclusion cases. But what do the 14 million people have in common who are actively seeking out Invisalign therapy today? There is bound to be some form of reliability in orthodontic treatment with Invisalign® if its consumer pool keeps expanding. This study investigates the truth behind Invisalign and its effectiveness with Class II malocclusion.

This study was published in the American Journal of Orthodontics.

Class II malocclusion correction with Invisalign: Is it possible?

Patterson BD, Foley PF, Ueno H, Mason SA, Schneider PP, Kim KB

Am J Orthod Dentofacial Orthop. 2021 Jan;159(1):e41-e48. doi: 10.1016/j.ajodo.2020.08.016. Epub 2020 Nov 19.

What they asked

This study aimed:

“To determine whether Class II malocclusion can be treated with clear aligners after completing treatment with the initial set of aligners.”

What they did

This was a retrospective study. They selected 80 Invisalign®-treated patients with a 90% of confidence level. All of the participants had finished treatment with the initial set of Invisalign aligners without known centric occlusion-centric relation discrepancies, issues of compliance, or overcorrection.

They divided the participants into two groups: (i) group 1 with Class I malocclusions (n = 40 [11 men and 29 women]; age, 38.70 6 15.90 years) and (ii) group 2 with Class II malocclusions (n = 40 [11 men and 29 women]; age, 35.25 6 15.21 years). For the Class II group, end-on and full-step molars as well as unilateral Class II relationships were all included.

They measured the digital model files at pre-treatment (T1), post-treatment ClinCheck prediction (T2A), and post-treatment (T2B) through the Invisalign website. They assessed seven measurements using the American Board of Orthodontics Model Grading System (ABO MGS) including alignment, marginal ridges, buccolingual inclinations, occlusal contacts, occlusal relationships, overjet, and interproximal contacts at T1, T2A, and T2B.

They also assessed the millimetric measurements for anteroposterior (AP) and vertical dimensions at T1, T2A, and T2B.

What they found out

They essentially found no improvements in the anteroposterior correction. The AP dimensions were 6.8% of the predicted amount in the Class II group. The amount of overbite correction achieved was found to be 28.8% of the predicted amounts in the Class I group and 38.9% of the predicted amounts in the Class II group.

However, the authors observed significant improvements in alignment and interproximal contact scores. Only a slight improvement was seen in the total ABO scores. They also found an increase in the mean occlusal contacts scores after treatment. None of the patients in the Class II group met the ABO standards after Invisalign treatment.

What we can conclude

Through this study, we are able to decipher that although the Invisalign system succeeds in achieving certain tooth movements, it fails to achieve other movements predictably. No significant Class II correction or overjet reduction could be observed with elastics for an average of 7-month duration in the adult population.

Additional refinements and increased treatment duration would be required to achieve an ideal occlusion. Therefore, it is up to the orthodontic specialist to inspect and decide on the patient management based on the extent of their Class II malocclusion case.