June 17, 2019

Are prefabricated Myofunctional appliances useful?

Wouldn’t it be great if you could simply take a functional appliance out of a packet and fit it to a patient without taking impressions?  This type of device is becoming more popular, but do they work?

Preformed myofunctional appliances have been used for several years.  The Myofunctional Research Company, in Australia, produces the most popular of these systems.  They target general dental practitioners in their marketing, and their appliances and philosophy are gaining popularity in the absence of evidence of their effectiveness.  In theory, these appliances correct malocclusion by addressing soft tissue problems. The advocates of this treatment also claim that they change the volume of the airway and treat childhood sleep-disordered breathing.

While the promoters of this treatment have not done any high-quality research on it. Some independent researchers have evaluated the effects of these appliances in randomised trials. I have posted about these before.

The EJO published this paper, which was a systematic review of the effects of these appliances.

Effectiveness of prefabricated myofunctional appliances in the treatment of Class II division 1 malocclusion: a systematic review

Hisham Mohammed et al

European Journal of Orthodontics, 2019, 1–10 doi:10.1093/ejo/cjz025


What did they ask?

This team, based in Edinburgh and Gothenburg, carried out this systematic review to answer the following question.

“What is the effectiveness of preformed myofunctional appliance compared to other forms of orthodontic treatment”?

What did they do?

They did a systematic review using standardised methods. These were electronic searches, hand searches, assessment of bias, data extraction, and relevant meta-analysis.

The PICO was:

Participants: 6-14-year-olds with Class II Division 1 malocclusion.

Intervention: Preformed myofunctional appliance

Comparison: Any active orthodontic appliance

Outcome: Amount of overjet reduction, any dento-alveolar changes, cost-effectiveness, airway changes and any adverse effects of treatment.

They wanted to include any randomised controlled trials (RCTs) and non-randomised studies (NRS).

Two independent investigators evaluated the papers and did the data extraction.  They assessed the risk of bias for the trials using the Cochrane Risk of Bias Tool and for the NRS, they used the ROBINS-Itool. Finally, they used the GRADE  approach to evaluate the overall strength of evidence.

What did they find?

They found 10 papers describing 6 different studies.  These included 3 RCTs and 3 NRS. When they looked at the risk of bias, they found that none of the RCTs blinded the examiners to the treatment allocation. This meant that they were all at high risk of bias. Similarly, they found that the NRS were at severe or critical risk of bias because of lack of control over co-founders, selection bias and lack of blinding.  They also found that two of the NRS were written up so poorly that they could not decide whether they were retrospective or prospective.

They presented their data as a narrative review with a limited meta-analysis. I will try to summarise this as simply as I can.

PMAs vs Activator. (3 RCTs)

  • The activator appliance was more effective in reducing overjet than the PMA in the short term. However, the mean difference was small at 1.1 mm (95% CI 0.44-1.77).
  • Both the PMA and the Activator improved lip seal.
  • One study reported that the Activator achieved a more significant change in ANB than the PMA. However, the differences were also rather small at approximately 1 degree ANB.
  • The activator treatment cost more than PMA treatment.
  • No studies reported on the airway.

PMA vs untreated controls (3NRS)

  • These studies were characterised by limited reporting of outcomes.
  • The PMA reduced overjets by 3.5mm compared to untreated control.
  • No soft tissue changes were reported upon.
  • PMAs did not influence the upper incisors, but they proclined the lower incisors.

They felt that the level of evidence from these studies was low.


Their conclusions were:

  • There were no clinically significant differences between the appliances
  • Activators were more effective than the PMAs in reducing overjet, but these differences were not stable in the long term and were not clinically significant.
  • The main advantages of the PMAs were reduced costs.
  • There was a high drop out and low acceptance rate for the PMAs.
  • There is an absence of evidence on stability and airway changes with any of the appliances.
What did I think?

I thought that this was an interesting and clinically relevant systematic review.  It was great that they were looking at a method of making treatment more straightforward.

When I looked at the results, I was interested to see that there were no marked differences between the appliances in terms of tooth movement, skeletal and soft tissue change.  Furthermore, because there is no need to take an impression and constructing the appliance, there appears to be a definite advantage of lower cost with the PMA.  However, the authors do point out there are relatively low compliance rates with the PMAs.  As a result, we may conclude that PMAs might be an effective method of treatment for Class II Division 1 malocclusion.

Nevertheless, we need to consider the strength of evidence. I must admit that I was disappointed to see that the three RCTs were at high risk of bias because of a lack of blinding.  This is a relatively basic methodological error.  Lack of blinding is fundamental because this may result in unintentional (or intentional) errors in recording data.  As a result, we need to bear this in mind when we consider the findings of the trials.


I feel that our only conclusion about PMAs is still that there is a lack of evidence on their treatment effects. While we may have an indication of their impact on the teeth, there is surprisingly no information on their impact on breathing, soft tissues, and sleep-disordered breathing.  As a result, there is no basis for the claims that are being made by their proponents.

I am also a little concerned that their ease of use may lead to remote prescribing or even in a direct to the consumer system of care. While we may feel that there is no risk of these steps being taken, nothing would surprise me with the developments that we are seeing in aligner therapy.

PMAs could be a significant orthodontic development. However, there is clearly a need for more research into their effectiveness. These trials are not challenging to carry out. I understood that Myofunctional Research is starting this work, but the silence is deafening. Is there anybody out there?


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Have your say!

  1. Clinical development officer at MRC here.
    Research is at the top of our agenda but many private practice orthodontists don’t understand the challenges of working for a multi national company that is rapidly growing. We are struggling to keep pace with staffing issues and all other complexities that come with a growing business, and as a result haven’t had the time to dedicate solely to research.
    Many people don’t understand the system or appliances, especially the critics. The appliances are a component of the system as a whole and the treatment should be delivered as a package. We don’t just sell appliances but we provide the education and highly specific protocol to go with it.
    Unfortunately some orthodontists view the appliances akin to functional appliances and therefore see them in the same light with the same inefficiencies regarding compliance.
    They don’t understand that they are to be delivered as part of a highly refined protocol which is all geared towards maximising compliance. Anecdotally we have about an 80 to 90 percent compliance rate in our clinics.
    If anyone would like to attend our clinics on the Gold coast and study our appliances without bias, you heard it here first, we are open to research and need help running them. Come study the system how it was intended to be used and come speak with us. We’re not as wacky as critics make out.
    Previously Kevin offered his services for I believe half a million pounds, which was out of our budget. Is this right Kevin?
    We thankfully have orthodontists using our system as an adjunct to their treatment from all around the world and we hope more will follow. If you are not addressing soft tissue and airway dysfunction, you are not addressing the most basic tenets of orthodontics that were taught by the most eminent orthodontists in history including angle, ricketts, graber and harvold, plus many many more. Even Proffitt in equilibrium theory, which Kevin recommends to his students to read, concluded with respiratory demands altering muscle equilibrium. None of what we do is controversial, and arguably should be mainstream, but we do understand that the system needs to be analysed more closely to help quantify and explain the changes we see in our clinics daily. Until then it doesn’t mean that the appliances don’t work, it just means that the mechanism of action is yet to be explained. If anyone has seen our cases you’d be in denial to not be impressed by what is achieved by wearing a prefabricated appliance for a third of the day, and not even every day (as compliance is never 100%). Preliminary studies have shown a positive change on the oral musculature and we hope these will be replicated at a higher quality.
    I recently met an orthodontist who was unsure about our methods and after 4 meetings with me and attendance of a course he is now wanting to implement it at his own clinic and is helping another clinic now treat over 150 patients. If you give us the time of the day with genuine interest to learn you will see we ain’t as wacky as people make us out to be. You always fear what you don’t understand.
    If you have any other questions I welcome anyone to contact me directly on [email protected]

    Thank you.

    • Emad,
      I am sorry to hear that your company is growing so fast that you do not have the time or resources to actually prove that it works. But then again, I understand the disincentive that is created by such a scenario, if people are buying your product anyway despite no evidence that it actually does what you say it does, why bother with research? I don’t think you are “wacky”….

      • I agree. If the company is growing fast. That means it has the potential to 1)make a lot of money and 2) either do patients a lot of good or a lot “bad”. So please do the responsible thing and start funding research to prove your product.

  2. Kevin an important point not mentioned is the burden (or not) of the treatment time. These devices are used over a long time spam (factor that explains the significant drop out). When reporting PROs treatment time is a consideration from the patient’s point of view. From our side it should be a factor considering the overall treatment cost. This may minimize the advantage of no impression time and cost.

  3. Interesting review and conclusions. How could it possibly be misquoted, or be used to promote PMAs?

    The “differences were not stable in the long term and were not clinically significant” and there “is an absence of evidence on stability and airway changes”. Why would any rational clinician use them?

    The cost of manufacturing a preformed mouthguard is considerable less that the laboratory cost of fabricating a custom “functional” appliance such as an activator. The cost of treatment may not be. In the home of the PMAs, costs can be anything up to $7,000 for “a full course of treatment”. Perhaps there is another reason for their use?

    Just remember, if it does not work because of the “high drop out and low acceptance rate”, the patient can be blamed for the poor compliance. If the patient has worn the PMA and the results are not impressive, just imagine how bad the malocclusion would have been without the “treatment”. It’s impossible for the clinician to lose!

    I see the “results” regularly and I must say that I’m not impressed and would never consider using one. A patient, who previously underwent a complete course of PMA treatment, has just had a mandibular setback. Her “normalised” breathing did not help her, perhaps she would have been worse but for the PMA intervention?

  4. Doc O’Brien,

    I posted this in an old blog you wrote but since I found your site by accident twice… i wanted to post it to your current discussion! Everything I wrote is still applicable, but I offered some food for thought to parents whom might find your article interesting. Of note, I am not a dentist.

    As a parent of three, one of my kids received standard (if such a term should be used) ORTHO care (braces), while my other two were recommended the MyoBrace by the pediatrics dentist. After reading the original blog posted, reading through the first 1/3rd of the discussion on the post, it’s interesting to see how discussion/arguments play out – call it a discussion or professional arguing between leaders in your fields and I think I found the same thing. Some people like it, some people don’t and others just ask.. what is the science behind it?

    As a parent, I ask some basic questions (a bit retrospective) – what was the reason this device is being suggested, what is the problem that the dentist identified and what do you expect to see this device do. As a scientist, I asked for the peer reviewed research that show valid application and results (this blog was the link – albeit, i found it after visiting the pediatric denist earlier today). But that is not what I received from the recommending dentist; aside from some cute side by side pictures of some test case that marketing pamphlets show “successful use”. We used it for over one year, and all but given up on the device. First and foremost, I think it should be mentioned that the Myo device was recommended by the pediatric dentist, and no consultation was made by an Ortho, an ENT or any other specialist that identified a specific problem that we needed to solve (I salute the posted comment by Caroline Fielden on your original article October 16, 2017 at 12:52 pm, who pointed out she actually consultated with ENT’s and other specialists outside of pediatric dentistry…) The dentist/company claim that within 6 months of use, the program should progress from the initial “training” devices to the hardened “jaw widening” adjustment device (I use quotes her to replace the techncial terms but the idea stands). After a year, we barely moved up one device – and that was by size only. After what should have been the deciding visit to “upgrade devices”, the tech only looked at her mouth, made my daughter walk back and forth, breath a bit and then said… “she is not ready”. That blew my mind. I was expecting something a bit more technical. I mean, this is a device that is supposed to be correcting some malocclusion (mis-aligned teeth for the layperson) however, no X-rays, no pictures, not even a side-by-side photographic comparative to show where we were, and where we are. Even if she took photos, never were they used to show us what was good/bad/indifferent. Red line crossed?

    You have got to know what medical issue you are correcting before just applying a blanket bandaide to all possible issues. Crowded teeth, snoring, hearburn, headaches, grinding teeth, 100 year old genetic adaptation because we don’t eat the same… Fear sells this device, when you tell a parent their child needs to be prepared to adapt their soft tissue to allow for… {fill in more technical dental medical terminology}… and this corrective device will help. “Will help”. it does not say it “will prevent”… “help prevent”… well, it may or may not… so fear based sales allows for this device to exist. No science to prove, and no one really disproved so is it a win-win? i mean, you pay and you don’t hurt anything?

    I digress. The point is, I really wanted to find out the answer to… should pediatric dentists be making recommendations and using devices that alter bone-face-muscular structure just because “they are familiar with the science of it”. More specifically, just because you take a class to have some familiarization in ortho-ENT-other specialization, is that something that you are supposed to be altering simply because “it’s a kid, so it’s pediatric”? If my kid needed some kind of serious ENT/ORTHO/Other consult, why was a device recommended without anyone else whom specializes in that said science consulted (obviously, I am asking this after the fact simply because as a parent, you trust the specialist you are taking your kids to). I just get a feeling that, like a pyramid scheme, MyoBrace was very good at marketing their product, and it seems if you are a believer it’s easy to just get into rhetorical arguments that has zero basis in attempt to not prove the device does good for all; instead, it simply distracts the discussion so no one has to point to actual evidence to prove the efficacy of use.

    Forgive me in advance, for my lack of complete knowledge of the dentistry field and by NO means am I wanting to get into a dentist to dentist to parent to patient to ORTHO to ENT to denist argument; I don’t know what I don’t know.

    • It is difficult to follow your comments.

      I hate to be cynical, but then I guess that I am have to live with it. Treatment is being provided by someone without adequate training or knowledge. I can only see two reasons. They are so busy and don’t have any interest or time to read, or are interested in the financial gain by providing treatment and do not care about anything else.

      This financial gain is true of all orthodontic treatments. One can only really be sure that the opinion being offered is not influenced by money, if the advice is to do nothing. For example, “all of the evidence shows that there is no benefit (to the patient) in early treatment and that the same result will be achieved with braces later, this will also reduce the duration of treatment“.

      A wonderful orthodontic researcher stated that most treatments work to some degree, and as a result there is often not much scrutiny of treatment. Even devices that don’t work, like the Myo, don’t raise the suspicion of the believers. As I often say, you don’t know whether something works until you stop doing it.

      Most orthodontists are well trained in science, but many still believe snake oil salesmen (KOLs). Paediatric dentists tend to believers and as such are more likely to use Myo appliances. Warm and fuzzy principles often reflect fuzzy thinking. Science is often cold but is more likely to be correct.

  5. @Kevin: Your concern as to ‘direct to the consumer’ is genuine: ‘Coz the ads here were claiming: ‘For open bites and deep bites, for crowdings and spacings, for class II and Class III, for cross bites and scissorsbites, for habits, use our single appliance- with advantages of: No impression required, no case/size selection required, no adjustment required’ – In fact when I was asked about these by general dentists during a mixed dentition lecture, I told them, hidden in the advertisement was the hint that “No dentist/orthodontist required!”.That summed it up subtly?

  6. Interesting topic. As a residency-trained orthodontist, I have noted with interest the great difference of opinion re: myofunctional positioners between orthodontists and dentists. Orthodontists have long used customized positioners for finishing tooth movement, but have eschewed generic positioners in favor of other types of function appliances, or fixed appliances. I associated in a practice that used generic myofunctional positioners in the mixed dentition to guide eruption and retain class II correction (usually done with a twin block or Herbst), and I have continued to use them in my own practice. It is a useful tooth-mover/bite retainer during the chaotic late-mixed dentition when it can be difficult to fabricate a well-fitting hawley or other acrylic appliance. I also feel that there is a benefit to encouraging proper lip-posture/lip-competence, especially in the maintenance of a class II div I. I have noted that compliance/success is negatively correlated with the size of the overjet. Very large overjets are very difficult to correct with a myofunctional positioner alone. I have found much higher success using a combination of herbst or twin block, which can be activated gradually over 6-12 months, then retention with a myofunctional positioner. It is not uncommon for these patients to not require Phase II due to the benefits of the positioner on the erupting dentition and the oral posture. So I’m glad attention is being paid to these appliances by the orthodontic community. I think we need to ask the right questions. They may be more difficult than another study on OJ reduction.

  7. As Carlos pointed out, some of the myofunctional appliance treatments went quite long; from 12-36 months! Also, Janson followed up myofunctional appliance treatments and found they dropped back to a net 1.5mm overjet change and crowding and overbite dropped back to basically the starting point. Is that cost effective?

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