November 30, 2020

Is Class II correction possible with Invisalign?

Surprisingly, there have been very few studies into clear aligners.  This new paper suggests that Invisalign is not effective for Class II correction.  But is the evidence strong, and is this a holistic evaluation?

Clear aligners are a well-established orthodontic treatment. I have posted several times about the effectiveness of this intervention.  Importantly, there have been few studies of large samples of treated cases. In summary, the general message from these studies is that aligners are not as effective as fixed appliances. Furthermore, operators may not readily achieve the predicted outcomes.   This new paper looked at the effectiveness of Invisalign in correcting Class II malocclusion.

A team from St Louis did the study. The AJO published the paper.

What did they ask?

They asked this question:

“Can Class II malocclusion be corrected with Invisalign after completion of treatment with the initial set of clear aligners”?

What did they do?

They did a retrospective study with the following stages:

  • They obtained the records of 80 Invisalign treated patients treated by a specialist with extensive experience with clear aligners (top 1% provider).
  • Next, they divided the group into 40 with Class I and 40 with Class II malocclusion (end on and full step molar relationships).
  • They collected data at pre-treatment (T1), undertook a ClinCheck prediction of the outcome (T2A) and post-treatment (T2B).
  • The outcomes were the ABO MGS scores for each stage.
  • They then calculated the change in score and the percentage of treatment accuracy.

I could not find much detail on the treatment process, particularly treatment protocols and use of Class II elastics in the paper. These protocols are an essential point, and I shall return to this later.

What did they find?

They produced a large amount of data, and I have extracted what I think is the most critical information.

  • Only 47% of Class I and 0% of the Class II cases would pass the ABO score assessment.
  • The mean start ABO score for the Class I group was 35.2, and treatment reduced this to 27.5.
  • The mean start ABO score for the Class II group was 55.98, and treatment reduced this to 48.7.
  • The  AP change was a mean of 1.25% in the Class I and 6.8% in the Class II group.
  • When they looked at the percentage accuracy of the tooth movement compared to the ClinCheck for the ABO scores, this was 21.9 % for the Class I and 17.7% for the Class II groups.

Their conclusions were:

  • Invisalign significantly improved both Class I and Class II malocclusions.
  • There were no improvements in Class II AP relationship for Class II problems when using elastics.
  • The ClinCheck predicted an ABO quality occlusion for the entire sample. However, the operator did not achieve this for any of the Class II treatments.
What did I think?

I have never done an aligner case.  This treatment was not suitable for my caseload of children with craniofacial and severe medical problems.  As a result, I have tried to approach this from a purely scientific point of view. So forgive me if I have misinterpreted the paper. Padhraig also contributed to the clinical comments below.

Scientific comments

I was not sure what to make of this study. My first concerns were that it was retrospective.  As a result, it must have considerable selection bias.  The authors did not provide any information on how they attempted to reduce this. We, therefore, must treat the findings with a degree of caution because we do not know the direction of bias.

I was also a little confused that they analysed the records after seven months.  I would not be consistently able to correct a substantial Class II relationship in an adult patient with fixed appliances in this time. Furthermore, we do not know the elastic protocol. We do not know if all the Class II patients wore Class II elastics. The mechanism of Class II correction used and the approach to the use of attachments to facilitate distal movement of the upper buccal segments is also not entirely clear. Nevertheless, it is a surprise that there was no Class II correction in this group.

Clinical comments

It was also interesting to see that none of the Clas II cases achieved an ABO pass score.  This finding is particularly relevant when we consider that the orthodontist was a top 1% provider.  I wonder if this reinforces the possibility that Invisalign is a compromise treatment? Or am I missing something, as I have never done an aligner case?

Equally, I wonder if this study represents a mid-treatment progress evaluation? We know that the changes predicted on the ClinCheck are often not achieved and that the ClinCheck might better represent a force delivery system rather than being an entirely realistic representation to tooth movement. Equally, Class II correction in adults is time-consuming. It is therefore likely that many of these cases will undergo considerable further refinement before completion. It would be very interesting to evaluate the predictability of Class II correction over the entire course of treatment. I, therefore, hope that the authors re-evaluate these cases after treatment.

Perhaps it may be more appropriate to conclude that ClinCheck software poorly predicts  Class II correction with Invisalign (at least for the protocol used in this study) and more efficient approaches to Class II correction do exist?

I think that there will be a lot of discussion about this paper. Let’s have a heated debate.


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Have your say!

  1. The fact that they have evaluated treatment outcomes just after completion of the first series of aligners makes the paper almost useless. It is, in my humble opinion, like to say that we just use one archwire or we refuse to reposition or bend for any teeth in fix appliances. On another note, being a big provider of clear aligners does not necessarily mean that the clinician is competent in using the appliance.
    Kind regards

    • A slight disagreement – looking at results after the first series of aligners does not make the paper useless – it makes the ClinCheck prediction useless for those who rely on it, use it to gauge treatment times etc. Furthermore if this is the result from a “sophisticated” aligner from an “experienced” doctor, where does that leave all the less experienced doctors, the ones who swallow the Holy Koolaid and just believe what they see in the ClinCheck, or even worse still, direct-to-consumer aligner treatment outcomes?

  2. First of all, I would like to thank you, Dr. O’Brien, for this blog. I find the information interesting and useful. Regarding the current topic. I am a board certified orthodontist since 2003. I am also a Top 1% Invisalign provider. I don’t expect to see the same results in the patient that I see on the Clincheck. To me, aligners are an appliance just like the straight wire appliance, which in my hands requires plenty of wire bending to achieve the results I want. I have been treating growing class II patients with aligners and class II elastics which great success for several years now. I routinely used a Herbst appliance prior to using aligners and I have been getting full correction of the class II, often in less time than my Herbst patients. In non-growers, unless the patient is only 2-3mm class II, they usually need extractions to correct the class II. I agree that more research is called for. Please continue your excellent work.

    • Thank you for restoring my faith in my professional colleagues it’s has taken a severe knock,
      I hear 1%ers boast about how they treat all of their patients with Invisalign even class 3 and especially open bite cases.In my location I am surrounded by Invisalign providers I learn a lot by providing second opinions not to mention the cases that have been in treatment for many years with no possibility of a result.
      How do they admit failure to their patients.I am 87 yrs old and still have an active case load.
      Regards class2. cases a s usual-there
      is no attempt to describe what class 2 is being treated ie div 1 div 2 open bite over closed they all require various treatment modalities.However I tend to treat class 2 cases with a Herbst then when I have molars in a super class 1 I usually have more than enough space for anterior alignment and finish in quick time
      The Herbst is the most effective appl. To treat class2s of any type
      A variation on this is exn of 2nd molars in the Mx.ia

  3. I agree that the evaluation period was too short. We will need further studies. Invisalign says it has many Cl II cases corrected by the appliance but no one publishes. This makes me a little bit suspicious.

  4. Anyone relying on the clincheck to evaluate actual class II corrections has no good understanding of what is a clincheck. The only valuable information the AP correction of a clincheck can give, in my opinion, is how the arches will coordinate “if the class II correction is achieved”. Like an oral surgeon would check the “fitting” of the upper and lower arch eith models when planning a surgery.
    I don’t understand why should clear aligners change anything in a class II case that we want to correct with elastics. Do braces correct class II’s?
    As far as I understand here, we are not talking about the Invisalign Mandibular Advancement feature. In that case, I agree with Dr Champagne that we need to see more studies.
    I would also be curious to see the ABO score of class II cases treated with fixed appliances by the same professionnal and how he/she would have evaluated success of his/her cases.

  5. Not finding fault. Rather, here I sit….. an enamel rod dancing through the matrix of life. Directly from the Invisalign site “over 9 million people, including more than 1.4 million teens, have used  Invisalign clear aligners to transform their smiles.” Beyond impressive case report wall-paper obviously, Align feels no real need to publish good evidence in respected refereed journals. Why? Suspected reasons include that the product has been so wildly financially successful that any real drive to prove their marketing claims is lost in balance sheets. Additionally, prior to diving into the deep-end, the dental/orthodontic community has certainly not required any solid proof of claims. In conclusion, if your peers aren’t looking then why bother with a burden of proof? It’s all rock and roll to me.

  6. I’m not sure there is any value in these types of “my appliance is better than yours” type of study. In a recent blog here it was decided that operator experience and appointment interval were more important than the wire or appliance used, which I would agree with. Anything that applies a force to the teeth will move them, anything that can jump the bite will do so in some cases. We know that braces move teeth, end of.

  7. Dear Prof,

    Thank you for your ongoing contribution to our profession. I enjoy your blog immensely.

    This study makes no sense to me. It seems to me that all adult patients with class 2 occlusions have 2 principle treatment outcome options.

    1. Maintian the class 2 occlusion and leave a residual overjet
    2. Correct the class 2 with any of
    a. Class 2 elastics
    b. Mazillary arch distalization
    c. Extractions
    d. Orthognathic surgery.

    Each of these options has various biological and mechanical challenges. But the appliance used to a very large extent is irrelevant. What class 2 correction was being evaluated? It appears perhaps 7 months of class 2 elastics? The Clincheck animation has nothing to do with this treatment modality or it’s predicatbility. I would be spectacularly unsuccessful if I tried to correct all class 2 malocclusions with 7 months of class 2 elastic wear and braces.

    I am uncertain why such a study would be presented for discussion in your blog Prof. It seems to me it offers no value in the assessment of class 2 malocclusion correction in aligners.

    All the best

  8. Thanks for the review Prof.

    As well as the study being restrospective, there are too many unknowns in this paper, most of them listed in the Discussion, with compliance being one of the main factors.
    I also agree with your point that a clincheck is a representation of the forces, not the final positions of the teeth.
    An interesting read nonetheless!

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