October 24, 2022

A new clinical study on Invisalign Mandibular Advancement.

Several years ago, Invisalign released its Invisalign Mandibular Advancement to treat Class II malocclusion. At that point, I wrote that there was little evidence to support the use of this appliance. However, it is great that some Invisalign clinicians have now produced an interim report on this treatment.

The Mandibular Advancement appliances incorporate precision wings into the upper and lower aligners. These are then advanced to achieve progressive mandibular advancement. This is, of course, similar to other functional appliances. This treatment method may have a scope as an invisible functional appliance.

A USA and Canada-based team did this study. The Journal of Clinical Orthodontics published the paper.

Prospective Multicenter Investigation of Invisalign Treatment with the MandibularAdvancement Feature: An Interim Report

Barry j. Glaser, Sandra Khong Tai,  Regina Blevins, Sam Daher,

Journal of Clinical Orthodontics: 2022 Volume LVI number 8 August edition.

What did they ask?

They did this study to;

“Test the safety and effectiveness of this appliance in growing patients with Class II malocclusion”.

The study team pointed out that this was an interim report.

What did they do?

They did a prospective multi-centre clinical study. The PICO was

Participants

60 orthodontic patients aged 11-19 with a fully erupted dentition. They had a bilateral Class II malocclusion of at least 3mm measured at the first permanent molars.

Intervention

Invisalign mandibular advancement appliances

Outcomes:

Dental and cephalometric measurements. The secondary outcome was the quality of life.

They collected data at the start of treatment (T1), end of mandibular advancement (T2), and end of treatment (T3).

What did they find?

They enrolled 60 participants in the study.  47 of them completed the mandibular advancement stage of treatment (T2). In addition, 25 completed all treatments at T3. 55% of the enrolled patients were female. The mean age was 12.75 at the start of treatment.

Class II elastics were not used in the mandibular advancement phase of treatment but in the final stages of therapy to T3.

These were the main findings:

  • The mean time to the end of the mandibular advancement phase of treatment was 12.6 months.
  • The total treatment time from T1 to T3 was 25.6 months.
  • These tables include cephalometric data on what I felt were the critical variables. I calculated the 95% confidence intervals, and these are in brackets.
T1 to T2 (n=47)
T1T2DifferenceP
ANB (degrees)5.46 (4.86 to 6.06)4.32 (3.67 to 4.97)
1.1 (0.21 to 1.99)0.0152
CoGn (mm)104.0 (102 to 106)107.0 (105 to 109)-3.0 (-5.9 to -0.0)0.0152
Overjet (mm)6.2 (3.47 to 4.73)4.1 (2.8 to 3.62.0 (1.18 to 2.8)0.0001
T1 to T3 (n=25)
 T1T2DifferenceP
ANB (degrees)5.11 (4.29 to 5.93)3.44 (2.5 to 4.38)


1.6 (0.07 to 3.3)0.0412
CoGn (mm)103.2 (100 to 106)106.8 (104 to 110)-3.6 (-7.7 to 0.5)0.0892


Overjet (mm)6.1 (5.32 to 6.88)2.7 (2.41 to 2.99)3.4 (2.5 to 4.2)0.0001

They concluded

“Invisalign MA seems to produce similar treatment results to other functional appliances”.

They also stated that mandibular incisor angulation is well controlled, and patients rate their discomfort as low.

What did I think?

First, it is good to see that the team has produced some data on this appliance, and they should be congratulated. Nevertheless, we must remember it is an interim report. As a result, we need to be very cautious in our interpretation. The authors have been clear on the nature of the information. However, I cannot help feeling they could have been more careful interpreting the data.

This is because we need to consider the following problems with this study.

  • There is no comparison with any other treatment or untreated control. This is important because we do not know the contribution of natural growth to the changes that they report.
  • The differences between the means are relatively low. For example, I would have thought that most functional appliances would have reduced overjet by more than 2.0mm in 12 months.
  • The confidence intervals are relatively wide. This reflects uncertainty in the data and is a result of the low sample sizes.
  • They did not report any information on 13 patients who were initially enrolled. This may have altered the data.

I am not sure when this study started, but the sample size appears low? I am also a little confused about the source of the data. When I first discussed Invisalign MA in my blog, Invisalign responded to my post. In this response, they provided data on 40 participants in their study in 2019. However, they also stated that 17,000 patients had used Invisalign MA. So I am struggling to understand why they only have data on 7 additional patients between 2019 and now?

Final thoughts

Finally, and most importantly. All the authors have a financial interest in Invisalign treatment. Unfortunately, they did not declare this in the paper. This is a major conflict of interest.

Ultimately, I still feel that we need better information on this appliance before we use it on our patients. I am unsure how long we will have to wait for a final study on this intervention to be published in a scientific journal?

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Have your say!

  1. Interesting results. I wonder how little or much effect it had in vertical growth itself as in AFH or MP. How different did it affect in high MP angle and low MP angle de patients.

  2. Research sponsored by Align favorable to Align products. When will orthodontists demand better?

    • It costs $ to do a study and for ANY new product in any industry the only ones who care to do the studies are the companies who are going to profit from that product. What we need to demand is that residents stop sending us questionnaires and then claim they got a master. This is exactly what universities should do. Nobody else has $ or interest. But residents should do real studies such as this to obtain a Master degree.

  3. An initial overjet of 6mm? I don’t think I would have bothered using either invisalign MA or a functional appliance for that! Interesting paper though.

  4. Cephalometric parameters (such as CoGn) exist in the minds of our orthodontic colleagues that use them; they don’t necessarily exist in real 3D space since the medio-lateral dimension has been arbitrarily reduced to zero thru superimposition.
    Moyers RE, Bookstein FL. The inappropriateness of conventional cephalometrics. Am J Orthod. 1979

  5. How much greater are these changes than what we would expect from normal growth at that age?

  6. agree about the 6mm OJ being a bit small. I think we need to catch ourselves on sometimes. In the desperation to do more braces more and more minor stuff gets done, it almost seems that there is no such thing as a minor malocclusion anymore. I’m sure we all get hundreds of referrals from worried dentists (not to mention patients) who see every small deviation from some arbitary normal as a case for braces (and they’re all doing invisalign remember, so if I won’t do it they will). The brace has become a desirable thing to wear as well, rather like someone wanting a cast on their leg without having a broken bone. Consequently long treatment times are ok since more braces must be better, even for one or two mms overjet change.

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