January 29, 2024

A new study shows Invisalign Mandibular Advancement is not effective.

I’ve noticed that there has been an increase in the number of papers published on clear aligners recently. Align has been promoting the use of Invisalign for teenagers and has also developed a new appliance called the Mandibular Advancement appliance. This serves as an alternative to other functional appliances. A team has published a new paper on the effectiveness of Invisalign Mandibular Advancement. Their findings suggest that this method may be ineffective in reducing overjets.

I have discussed this appliance before, as previous research has produced conflicting results regarding its effectiveness. Nevertheless, the company and its paid clinical salesmen are still promoting it. In an earlier post on the mandibular advancement appliance, I wondered when we would see further research on this appliance. A team from Adelaide, Australia, recently conducted such research, and the AJO-DDO has published their paper.

What did they ask?

They did this interesting study to ask.

“Did the use of the MAA achieve the predicted changes in overjet and molar relationship”?

What did they do?

They carried out a retrospective analysis of collected case records. The study had the following steps.

They accessed the Australian Aligner Research Database. This database contains information on Invisalign treatments that 16 experienced orthodontists did. This included records of 16,500 patients.

The team used the following inclusion criteria to select the patients for this study.

  1. They had an initial phase of Mandibular Advancement treatment
  2. Complete STL digital records at the start of treatment and the end of phase I treatment to correct the Class II malocclusion.
  3. The patients were compliant.
  4. They also needed an initial set of aligners to complete the treatment

They collected standard demographic data of the patients.

Finally, they recorded the planned and achieved overjet and molar relationship from the ClinChecks. This enabled them to collect data on the deviation from the achieved and planned tooth movement. This was the primary outcome of the study.

What did they find?

The team identified 195 patient records after excluding 103 without final records. The mean age of the patients was 12.62 years old, and 53% were female. The orthodontists used a mean of 40.2 aligners.

When they looked at the tooth movement, they found.

  • The treatment reduced the initial overjet from a mean of 6.49mm to 4.61mm. This was 42% of the planned outcome.
  • 47% of the patients had an overjet greater than 4mm at the end of this phase of treatment.
  • The anteroposterior molar correction was 31% of what they planned.

This is not much to write home about…

Their conclusion was;

“Less than half of the planned overjet reduction and less than a third of the planned AP FPM correction were achieved with the MAA. Almost 20% of patients completed the MAA phase of treatment with an increased overjet despite a planned reduction”.

What did I think?

This large and ambitious study was a step forward for aligner research. As a result, it is important. The study findings and conclusions are somewhat controversial, and I have some concerns about the study. It is also good to see that the research team has highlighted these concerns. These are

  • There is selection bias in this retrospective study due to the exclusion of 103 (34%) eligible records. However, it is important to note that the direction of this bias is unknown, which results in a significant degree of uncertainty.
  • The study reports on the results at the end of the first phase of treatment, which is consistent with other studies on functional appliance treatments. Nonetheless, it is worth keeping in mind that these results are only interim outcomes since additional treatment may still be required to reduce the overjet.
  • Moreover, I am uncertain whether we can consider the deviation from the planned ClinCheck outcomes as an outcome measure. There seems to be increasing agreement that the ClinCheck represents a force system and should not be employed in this manner. Specifically, the ClinCheck involves a component of over-treatment, similar to increased COS to reduce an overbite.
Further thoughts

I have thought about these issues, and when we consider that the primary goal of phase I is to decrease the overjet, it’s safe to conclude that MAA treatment failed to achieve this objective. This finding is also consistent with another study that looked at the effectiveness of the MAA. 

I am not completely convinced about using ClinCheck deviations as a reliable outcome measure, because there is a risk of misinterpreting the data. I would prefer if researchers used a well-established outcome, such as PAR or the ABO index. However, we cannot ignore the fact that this study demonstrated unsatisfactory reduction of overjet in many patients. We need to discuss the pros and cons of using ClinCheck deviations as an outcome measure.

I would like to conclude with my regular comment regarding clear aligners. It would be highly beneficial if someone could carry out a trial using a final treatment outcome measure such as the PAR or ABO index. This trial is not difficult to do, and it would help us to determine the truth about the effectiveness of clear aligners. Unless we are not interested in discovering the truth? I’m still looking for pigs on the wing.

Final comments

This paper represents the highest level of evidence on the use of MA in phase I of Class II treatment that has been published. It suggests that it is not very good. I would stick with the Twin Block for Class II treatment.

Have your say!

  1. This is purely anecdotal…..but after a large amount of deliberation and research on my part, I decided to embark on aligner treatment (for my 12 year old son) ,privately, in the UK) as a costly alternative to twin blocks and metal braces. He commenced treatment JUly 2023. Initially, he was unable to have the MA part of the treatment, as he had milk teeth in places where the ‘wings’ of the MA appliances can only work with adult teeth in situ. So, he commenced treatment with just standard aligners.

    Then, in October, our Orthodontist called us in for an appointment and advised us that she was now offering us Angel Aligner therapy (first in the UK I believe) with MA, as Angel Aligners do allow for the MA appliance to be fitted before all adult eeth are in.

    Since October, and the commencing of the MA Angel Aligners, with attachments also, we have witnessed huge progress. My sons overjet was measured by two different Orthodontists before we started treatement, at 12 and 15 mm respectively. So it was significant. It has already shifted to around 9mm and that was at the last appointment over Christmas time. He is only 13 weeks into a planned 33 week intervention, and our Orthodontist is astounded by his progress and delighted and has no concerns whatsoever that it is not working just as it should.

    We clearly have many weeks of treatment to go. From a laypersons perspective, I will say that even at this stage, we believe our son’s bit to look seismically better than it did before. He was getting teased in school because of his protruding front teeth, and he has received no teasing since November – as essentially now his front teeth no longer appear to protrude as they did.

    We have no expereince of twin blocks or metal braces at all, but I would add that my son finds the clear Angel Aligners to be comfortbale and super easy to fit and remove. He is able to keep up his excellent oral hygiene with this system and you literally cannot tell he is wearing anything. Other changes, such as palate expansion and such things also seem to be working seemlessly too, thus far.

    I realise this is far from over for us, and is also only a case study of one boy. However, after I agonized over which choice to make with him, NHS twin blocks and then braces or expensive Aligner treatment, I just thought I would share our story so far. We could not be happier at this point.

    • Adam, thanks for sharing your son’s story. I also have a good experience with the MA device, the boy grew quickly at the same time – growth spurt. The father and the patient were very satisfied. Final Overjet was smaller then planned. We used posterior buttons and elastics some months to close posterior openbite. The result achieved and remained over 3 years, only Vivera, no night elastics.

      I think, the right MA protocol and timing are important.

      • Riina, thanks very much for sharing that, very reassuring. I believe my son is the first UK child to receive Angel Aligners with MA. He hasn’t needed any elastics as yet, but if he did Angel Aligners have a distinct advantage over Invisalign, as they allow for buttons to be an actual integral part of the Aligners…so no bonding required and no risk of breakages etc.

  2. Interesting findings for me!

    In our study club, we’re seeing great results. Is it patient selection ? Is it treatment protocol ?

    Mean age of 12,62 years old appears a little old for me.
    Similar studys for twin blocks usually include patient with mean age of 10-11 years old.

    When growth is done, it won’t work, right ?

    • So does that mean that age span for boys vs girls will differ? It seems like 12.6 would be fine for boys. I am hoping this is true as my boy 12.5 just started on this treatment.

  3. Thank you for this summary.
    The usual deal: all you can eat buffet of unlimited aligners, you get 50% of planned movements!!

  4. Surprising revelations in this research seem to be:

    *47.7% of patients finished this stage of treatment with greater than 4mm of overjet.
    If half our class II patients finished with greater than 4mm of overjet, would any of us consider those patients to have had successful treatment?
    *The mean change in the molar relationship was just under 1mm, as measured at the MB cusp.
    Do any of us consider a modality that achieves a mean change in molar relationship of 1mm a reliable treatment for class II correction?
    *19.5 % of patients actually finished with more overjet than they started with.

    Let’s ignore for just a minute what all of us likely by now realize, that functional appliances do not grow mandibles. Given the above, let’s also ignore our individual biases as to whether or not we believe the class II correcting dentoalveolar effects, and HG effects, of functional appliances make them worth using on patients or not worth using on patients.

    No matter which side of that coin we are on, use functional appliances for their dentoalveolar and HG effects or don’t, this research seems to show that Invisalign MAA does not seem to be a reliably successful means of class II correction. I am guessing that most of us consider 4mm of overjet a failure.

    While we are on the subject of comparing Invisalign MAA to other functional appliances, I wanted to offer a possible alternative explanation as to the claim that MAA “offers superior control of mandibular incisor angulation (torque)”.

    The dentoalveolar effects of non-MAA functional appliances have the known side effect of flaring the mandibular incisors. As Invisalign caps the mandibular incisors, and that seems likely the reason lower incisor torque is maintained, it seems entirely possible that with MAA, the mandibular incisor roots are being translated right outside the facial cortical plate instead. Tipping the lower incisors facial, secondary to the dentoalveolar effects of other functional appliances is generally not the best side effect. However, translating the entire mandibular incisor roots outside the facial cortical plate, as seems quite possible from the dentoalveolar effects of MAA, would be a far worse situation.

    With Invisalign, the rule of getting the opposite of what we want with incisor torque seems to often apply. When we want maxillary incisor torque to be maintained, as with upper bicuspid extractions, the appliance does not produce the moment to force ratios needed. When we don’t want incisor torque to be maintained, was with the dentoalveolar effects of functional appliances, the MAA appliance maybe just does translate the roots.

    This is just my theory as to what is happening with the lower incisor roots with MAA. Quite obviously, there is no research either way on this. IMO, this shows another of the dangers of releasing an appliance for general use, with all the marketing and regalia, though without the scientific evidence to support it.

  5. There are no dates as to when these cases were done.
    The MA feature when first released had lots of failures, which is probably when this data was obtained , but of that I’m not sure.
    The new design of “wings” is way better.
    So if your just reading this article without understanding this you could very well be misled.
    It certainly works in my hands .

    Fully agree we need more research as Prof suggests .

  6. I’ve seen pretty good outcomes long term with MA- but you have to hold it LONGER than the techs often do and overcorrect and then “deprogram” Certainly better than with TB and less damage and discomfort than with a herbst/forsus- better patient expereince

  7. Just to add- yes, if you’re doing the study at a mean age of 12.5 and not factoring out the post-pubertal patients, it’s a “trash” study! We’re using MA on much younger patients and having great outcomes supported with the numbers.

  8. Hi all,

    I would like to provide some context about which you can frame your comments/criticism.
    1. If you read the paper you will find the average age matches those for twin block studies and those eg done by Align’s KOLs (Glasser et al 2022 AJODO). It is interesting that online comments have been both “sample is too old AND “sample is too young”.
    2. The cases were drawn from a database of 17 orthodontists, all 10+ years aligner experience, 9 of whom are/have been KOLs for Align and 9 (some overlap) hold some form of academic position. One would think they might know what they are doing?
    3. The other papers on MAA – including Glasser et al have reached very similar conclusions, and all we have to put against the “evidence” are corporate claims and anecdata. Yes the evidence is not excellent. On the other hand, what we do not have is evidence of excellence either.
    4. If you have evidence of excellence you should indeed publish it in a peer-reviewed journal for the benefit of everyone.
    5. Since “a lie gets 1/2way around the world while truth is still getting its pants on” and we were investigating the claims made for SUPERIOR efficacy of MAA made by a company, I think that maybe we have helped the truth to get its pants on a little faster.
    6. We have “put our cards on the table”. It is up to you to decide what to do or believe, hopefully having read ours and the other papers on the subject, and, if you do have evidence to the contrary, publish it. Indeed, I will help you to do so, since it is the truth we are after, but you would have to provide me with ALL the data you have. My email is [email protected]. Surprisingly when I make this offer to people who claim different results I have not, so far, had a single person willing to take up the offer.

  9. Thank you for this observation. I have yet to read and experience myself with my growing patients. I started working with Angel Aligner and they have this Mandibular Advancement as well.

  10. Both of my children (ages 11 and 13) are struggling with a proper bite following 6 months of use of Invisalign with Mandibular Advancement. The overjet is clearly gone, but their incisors touch while a posterior open bite exists. The orthodontist has recommended not wearing any aligners. After 3 weeks, we are seeing the posterior open bite improve. The mandibular incisors are now slightly posterior to the maxillary ones. We essentially ended up with an underbite following MA.

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