Myofunctional appliances are cost effective: A new trial

A couple of weeks ago I published a very popular post on myofunctional appliances.  This post is about a new trial that looks at their cost-effectiveness.

A myofunctional appliance is an intra oral appliance similar to a positioner.  Its main advantage over other appliances is that it is preformed. As a result, we can fit it without taking impressions and getting the appliance made by a technician. In theory, this is great.  I have based this post on a second paper from a trial that I have previously discussed.  Emina Čirgić and a great research team from Gothenburg, Sweden did this study.  The European Journal of Orthodontics published the paper.

A cost-minimization analysis of large overjet reduction with two removable functional appliances based on a randomized controlled trial

Emina Čirgić et al

European Journal of Orthodontics, 2017, 1–7 doi:10.1093/ejo/cjx077

The team asked this question;

“Was there a difference in the costs of reducing large overjets with a preformed myofunctional appliance or an Andreasen Activator”?

What did they do?

They did a large multi-centre RCT in a general dental practice setting. The PICO was:

Participants: 97 children with a mean age of 10.3 years (SD+1.64) with an overjet of greater than 6mm.

Intervention: Myofunctional appliances

Comparison: Andresen Activator

Outcomes: Success of treatment and societal costs of treatment. This included the Direct costs (chair time) and Indirect costs (Parent time and costs).

Randomisation, concealment and allocation was clear. They collected and analysed the data blind.

General dental practitioners provided the treatment under the direction of an orthodontist. This is standard delivery of care in Sweden.

They asked the participants to wear their appliance nightly and for 2 hours during the day. This was for a total of 12-14 hours.

What did they find?

They classified successful treatment as a final overjet of less than 3mm.  If the overjet was not reduced at all, they classified the treatment as unsuccessful. The mean treatment duration for the Andresen was 1.5 years and for the myofunctional appliance it was 1.2 years. This was not statistically significant.

They achieved a successful treatment outcome for only 37% of the participants.

I have extracted the process data into this table.

 ActivatorMyofunctionalDifferencep
Number of visits11.45 (10.4-12.6)8.4 (7.7-9.2)3 (1.5–4.5)<0.001
Emergency visits0.7 (0.4–1.0)0.1 (0.03–0.2)0.6 (0.3–0.9)0.6 (0.3–0.9)
Chair time (mins)245 (213–277)167 (149–185)167 (149–185)<0.001
Costs (Euros)1548 (1366–1730)974 (876–1071)574 (385–764)<0.001

Their overall conclusions were

  • Myofunctional treatment is more cost-effective than activator treatment. This was because there were no technicians costs and there was a high number of emergency visits for the activator patients.
  • Both appliances had a low overall success rate.
What did I think?

I thought that this was a really ambitious study that they did in a “real world” setting. This was not easy.  Importantly, this study provided data on the costs and process of treatment. These are very useful outcomes for both ourselves and our patients. Again, it was great to read a “functional appliance” paper that did not have any cephalometrics.

I am being very critical, but I spotted that they allocated  more patients allocated to the myofunctional appliance than the activator. This suggests that there may have been a problem with the randomisation. As a result, this study may have some bias.

I would really have liked to see the Twin Block studied in this way and maybe this is another study.

I cannot help feeling disappointed at the low success rate for both of the interventions. When we have done studies with the Twin Block the overall failure rate was about 20%.  However,  specialists did these treatments and they may be more likely to be successful with the treatment than general dental practitioners. However, this is just conjecture.

One criticism that I know will come from the myofunctional physicians/orthodontists is that the practitioners did not prescribe any of  the breathing exercises that they recommend.   I  hope that another study can be done that includes the exercises.

Final comments

Finally, this is a great example of a study that can be done on myofunctional appliances.  Perhaps the myobrace “scientific advisor” or the company could start working on similar studies. This just needs time, effort and a willingness to randomise.

I think that I would use myofunctional appliances, if other trials showed a higher success rate. In the meantime, I will continue to use the Twin Block because of the evidence from trials on its effectiveness.

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  1. As an advanced Ortho tech working through the 80s etc there were many Myofunctional device design some complex and fun to make! Have all these been diluted to an off the shelf device?

  2. Thanks Kevin.
    I thought the consensus now is that functionals do not grow jaws and so it doesn’t matter which one we use, if any. All we have to do is pray for growth and maybe keep the teeth apart when it happens. If this is the current opinion (ie normal growth allows bite jumping in some cases) how about testing it with a functional v an upper posterior bite plane (the old bite plane effect), posturing the jaw forwards should be unnecessary. We also need to be realistic about success rates, 37% sounds about right to me; if only there were a way to know who will grow and who will not so as to avoid functionals that don’t work. I suppose we could just wait for growth and treat after with extractions, is this better?
    It seems that we are still wedded to our functionals despite the evidence that they do not grow jaws ( even still calling them myofunctional ) when there may be a simpler option for our long suffering patients.

  3. Thank you Kevin

    The study seems to have missed the mark. Where will patients end up? Will they need fixed appliances later? If so, will there be a difference between three groups, i.e. Myo, “functional” and no early treatment? What is the real cost of all treatment needed?

    Why not compare Myo treatment with a hammer or magic chewing gum. If is more effective at reducing overjet in the mixed dentition in a third of patients, then must be worth prescribing or researching? Not sure Lysle Johnston, the only one who seems to be prepared to have an opinion on and not pander to warm “fuzzy logic”, would agree.

    Is it not time that we had an honest opinion and stopped wasting time with treatments that have no scientific basis? Or should we also continue to research self-ligation and mouth vibrators? Wasting time researching and discussing Myo appliances just gives the promoters more opportunity to sell their snake oil. I breathe and my face grows. I see brachyfacial patients who have been referred by Myo practitioners to have tonsils and adenoids removed because they are “mouth breathers”. Surely, if we believe their bizarre theories, we sould force these patients to “mouth breathe” and change tongue posture, in an effort to increase the vertical growth?

    We are a mature specialty and should start acting that way.

  4. Interesting discussion. Thanks for posting this Kevin. Just a couple of points;
    1. In my limited experience with these devices, one of the main deficiencies is the lack of retention. This might explain the low success rate to some extent.
    2. The discussion needs to define ‘growth”. Since we now have 3D digital data and mathematical modeling, we can decompose the effect of size-change, shape-change and translation thru 3D space (Spatial matrix hypothesis; Singh 2004, Craniofacial Growth Series), using appropriate software. This permits us to determine what happened, where it happened and by how much (localization of allometry after scaling), and sometime yields surprising results devoid of (clinical) optical illusion (Singh and Clark 2001, Amer J Orthod Dentofac Orthop).
    3. If these devices re-position the mandible, they might be expected to have an effect on the upper airway – if so, tonsils and adenoids may not require surgical removal if the mode of breathing can enhance antimicrobial NO (nitric oxide) production, which might help regress the hypertrophic tissues in pediatric cases.

  5. I have to second Dr. Attric’s opinion. Unfortunately, the myo-folks are unwilling to use the scientific method in debate, and instead tend to rely on appeals to emotion, hyperbole or pseudo-science to make their points. There’s an a priori bias that seems impossible to overcome, and this coupled with all the smoke and mirrors and science denial makes for a rather frustrating debate. We need to move past “Do No Harm”, into “Show me the benefit”.

  6. Kevin you’d need to learn myofunctional therapy, understand fully how the jaw grows, osteology, anthropology, epidemiology, pulmonolgy and how to use the tongue to properly use myobrace. Medicine is not a pick n’mix, paint by number system and knowledge like this cant be accrued from a text book or quantified through existing software. It needs life experience and a huge paradigm change. Perhaps start by mouth breathing chronically for a year and you might accrue some real applicable experience. You may also be enlightened to understand why so many take dysfunctional breathing so seriously.

    • I worry about the validity of therapies based on “life experiences “.
      These are certainly important but well conducted studies are vital for us to have a viable ,respectable ,clinical ,scientific basis .
      If nothing else ,this excellent blog has reinforced this opinion !
      Thanks for allowing the input!

  7. What do people think of this article? See below. I wish I could send as an attachment. If you’d like me to send the full article and I have another from Tufts, please let me know.

    It’s a little different as it doesn’t use the generic preformed myofunctional appliance as it used a eruption guided appliance (Occlus-O-Guide) but the results are pretty impressive and it does empirically show increased mandibular growth in the treatment group by 3.9mm vs the control: A Summary of “Dentofacial Changes after Orthodontic Intervention with Eruption Guidance Appliance in the Early Mixed Dentition” Keski-Nisula, K. Keski-Nisula, L., Salo, H., Volpio, K. & Varrela, J., Angle Orthodontist, 78: 324-331, 2008.

    Orthodontic intervention in the early mixed
    dentition: A prospective, controlled study on
    the effects of the eruption guidance appliance
    Katri Keski-Nisula,a Riitta Hernesniemi,b Maritta Heiskanen,c Leo Keski-Nisula,d and Juha Varrelae
    Vaasa, Kurikka, Jalasjärvi, Tampere, and Turku, Finland
    Introduction: A prospective, controlled cohort study was started in 1998 to investigate the effects of
    orthodontic treatment in the early mixed dentition with the eruption guidance appliance. Methods: Occlusal
    changes were recorded in 167 treated children and 104 controls after they had reached the middle
    mixed-dentition stage. Treatment began when the first deciduous incisor was exfoliated (T1) and ended when
    all permanent incisors and first molars were fully erupted (T2). The children’s mean ages were 5.1 years (SD
    0.5) at T1 and 8.4 years (SD 0.5) at T2. Results: From T1 to T2, overjet in the treatment group decreased from
    3.1 to 1.9 mm and overbite from 3.2 to 2.1 mm. In the control group, overjet increased from 2.9 to 4.1 mm
    and overbite from 3.3 to 4.1 mm. At T2, the differences between the groups were highly significant (P .001).
    At T1, 18% of the children in the treatment group and 22% of the controls had tooth-to-tooth contact
    between the maxillary and mandibular incisors. All others had an open bite, or the mandibular incisors were
    in contact with the palatal gingiva. At T2, tooth-to-tooth contact was observed in 99% of the treated children
    and 24% of the controls (P .001). Almost half of children in both groups showed incisor crowding at T1.
    Good alignment of the incisors was observed in 98% of the treated children at T2, whereas maxillary
    crowding was found in 32% and mandibular crowding in 47% of the controls (P .001). At T1, 41% of the
    children in the treatment group and 53% of the controls had a Class I relationship; the rest had either a
    unilateral or a bilateral Class II relationship. At T2, a Class I relationship was found in 90% of the treated
    children and 48% of the controls (P .001). At least 1 occlusal deviation, including overjet 5 mm, overbite
    5 mm, open bite, gingival contact of the mandibular incisors, crowding, or Class II relationship, was
    observed in 13% of the treated children, but the deviations were mild, and no child was considered to need
    treatment. In the control group, 88% of the children showed at least 1 occlusal deviation (P .001).
    Conclusions: Treatment in the early mixed dentition with the eruption guidance appliance is an effective
    method to restore normal occlusion and eliminate the need for further orthodontic treatment. Only a few
    spontaneous corrective changes can be expected without active intervention. (Am J Orthod Dentofacial
    Orthop 2008;133:254-60)

    CONCLUSIONS
    The results indicate that orthodontic intervention
    with the eruption guidance appliance in the early mixed
    dentition is an effective treatment modality for malocclusions
    with Class II or Class II tendency, excess
    overjet, deepbite, open bite, crowding, anterior crossbite,
    or buccal crossbite. During the treatment, the
    erupting permanent incisors and first molars were
    guided into their correct positions in the dental arches.
    At the same time, intermaxillary relationships in the
    incisor, canine, and molar segments were largely corrected.
    During the observation period, only a few
    spontaneous corrective changes occurred in the control
    children. By the time the children reached the middle
    mixed dentition, little treatment need was left in the
    treatment group compared with the control group,
    where deviating occlusal characteristics were commonly
    observed.

  8. As always a fascinating ,valuable and educational insight into a clinical study.Thanks.I do feel ,however , that the appliances studied are of historical interest only. Both appliances have been shown ,both in terms of final outcome ,efficiency and compliance (“bulky “) to be of little ,pratical use in most geographic locations.I may be missing something (quite possible !) BUT what is the point ,given the above ,of spending time and resources on comparing 2 ,out of date ,appliances that are hardly used in practice?

    • I’m not sure how a 9 year old study over 3 years is considered out-of-date and I’m not sure how it’s been concluded that it has little practical use in most geographic locations. In any case, they are still very widely used and I think it could be argued that they are much more effective than other preformed, non-tooth specific appliances that only achieve mediocre results. Plus, these actually have bona fide clinical studies confirming their orthodontic efficacy. If anything these appliances were ahead of their time in that they prevent and correct malocclusions very easily and passively before those conditions worsened. Also, if you’d like a more current study, this one was done in 2014:

      Randomized controlled trial
      One year treatment effects of the eruption
      guidance appliance in 7- to 8-year-old children: a
      randomized clinical trial
      Rita Myrlund*, Mari Dubland*, Katri Keski-Nisula** and Heidi Kerosuo*
      *Institute of Clinical Dentistry, Faculty of Health Sciences, University of Tromsø, Norway, **Department of Oral
      and Maxillofacial Diseases, Vaasa Central Hospital, Finland
      Correspondence to: Rita Myrlund, Dental Health Service Center for Northern Norway (TkNN), PO Box 2406, NO-9271 Tromsø,
      Norway. E-mail: rita.myrlund@tromsfylke.no
      Summary
      Background: The eruption guidance appliance (EGA) aims to correct sagittal and vertical occlusal
      relations concomitantly with alignment of the incisors. Few reports have been published on
      treatment effects with the EGA but no randomized studies have been available.
      Objectives: The aim was to find out if 1 year active treatment time with EGA was sufficient for
      achieving normal occlusal relationships and dental alignment in 7- to 8-year-old children.
      Participants, study design, and methods: Eligibility criteria for participants were: fully erupted
      upper central incisors, and Angle’s Class I or Class II molar relationship combined with any of
      the following traits: deep bite, increased overjet ≥5 mm, moderate anterior crowding with overjet
      ≥4 mm. After screening of 148 children, 48 7- to 8-year-old children were recruited in the study. The
      participants were randomly assigned into a treatment group (N = 25) and a control group (N = 23).
      Children in the treatment group received treatment with the EGA for 1 year. The controls had no
      orthodontic treatment. Changes in overjet, overbite, Angle’s Class, and crowding were used as
      primary outcome measures. Occlusal assessments were performed on dental casts obtained from
      all subjects at start of the study (T1) and after 1 year (T2). Lateral cephalograms were obtained
      from all subjects at T1 and from the treatment group at T2. All measurements on dental casts and
      cephalograms were carried out blinded.
      Results: Forty-six children completed the study. Mean overjet and overbite decreased significantly
      in the treated subjects during 1 year, in contrast to a slight increase in the controls. Class II molar
      relationship decreased from 46 to 4 per cent in the treatment group, with no significant change in
      the control group. Mandibular anterior crowding decreased significantly in the treated subjects,
      while the controls showed a slight increase.
      Conclusions: In short term, the EGA seems to be effective in correcting increased overjet and
      overbite, Class II malocclusion, and lower anterior crowding in the early

      • Good comments ,much appreciated BUT I am not able to charge Pts /Parents for anything with a 37% success rate (put simply).These appliances certainly were ahead of their time when first used -several decades ago !
        My thoughts may be based on the practice envoirenment I deal with in Canada.
        I am not sure what “non-specific tooth appliances “are but many thanks for the comments.Any discussion always teaches me something !

  9. The design of the study is good. The statical and the analytic process of the data were a strong methdology. In my opinion the complete address of the malocclusion was not clear, some overjet cases can be easily treated by stoping oral habit , however other skeletal class II malocclusion associated with increased overjet will require different mechanics and growth modification to be implemented. Functional appliance has tremendous dental and skeletal correction of class II malocclusion.