A new trial on myofunctional appliances.
One of the most controversial areas in orthodontics is the use of myofunctional treatment. While I have been critical of the evidence base underpinning this several times, I have also suggested that this treatment may have an effect. Nevertheless, we need to see some new studies. This new trial was flagged up to me, and I thought that I should have a very close look at it.
Myofunctional treatment has been defined as:
“Therapy of dysfunctions of the muscles of the face and mouth to improve orofacial functions such as chewing and swallowing and encouraging nasal breathing”.
Over the past 10 years, this treatment has been gaining popularity. Subjectively, most of this treatment appears to be done by general practitioners; however, specialist providers are now considering it to treat children with disordered breathing. This study looked at the effects of this treatment on a large sample of children.
A team from China did this study. BMC Paediatrics published the paper.
BMC Paediatrics. (2022) 22:506. https://doi.org/10.1186/s12887-022-03559-w
What did they ask?
They did this study to answer this question.
“What are the clinical effects of myofunctional treatment on children with mouthbreathing by cephalometric radiographs and study models”?
What did they do?
The team carried out a non-randomised concurrent controlled trial.
The PICO was:
Participants:
224 young patients aged 5-10 years with a normal body mass index, class I molar relationship, skeletal Class I and normal vertical facial growth.
Intervention.
The patients were divided into three groups
- Functional mouth breathers who had myofunctional treatment (n=75)
- Mouth breathers with no treatment (n=70)
- Nasal breathers with no treatment (n=79).
They based the treatment allocation on clinician and patient preferences. Notably, the functional mouth breathers with no treatment were placed in that group because the parent and child declined treatment.
Outcome
Cephalometric and study cast measurement at the start and end of treatment.
The patients were diagnosed as mouth breathers by an otolaryngologist physician from physical examination and patient history.
The nasal breathing group breathed through their noses but had mild malocclusions, and the orthodontist recommended regular visits. However, I think that they did not receive treatment.
The children in the myofunctional treatment group were asked to do myofunctional exercises and wear a Myobrace appliance for 2 hours during the day and night while sleeping.
The team did a sample size calculation based on detecting a difference of 1.47mm in overjet.
The statistician analysed the data with a paired t-test and analysis of variance.
What did they find?
The mean duration of myofunctional treatment was 13 months.
The team presented much cephalometric data with many measurements tested several times. They also presented data within and between the groups. I found this confusing and decided to look at the data simply.
Firstly, there were no fundamental differences between the groups at the start of treatment. I then looked for any differences between the groups at the end of the treatment. This is a logical step because if there were no differences at the start, any differences in the final outcomes should be due to the intervention or average facial growth. I extracted this information from the three highly detailed tables of cephalometric measurements.
| Outcome | Mouth breathing (treatment) | Mouth breathing (no treatment) | Nasal breathing (no treatment) |
|---|---|---|---|
| SNA (degrees) | 82.65(1.67) | 82.97(1.26) | 82.96(1.47) |
| SNB (degrees) | 80.0 (1.66) | 79.76(1.37) | 80.4 (1.53) |
| ANB (degrees) | 2.61 (0.65) | 3.21 (0.73) | 2.56 (0.83) |
| FH-MP (degrees) | 31.3 (3.0) | 32.29 (1.09) | 30.09 (1.5) |
| Overjet (mm) | 3.03 (0.66) | 4.34 (0.91) | 3.18 (0.48) |
| Overbite (mm) | 0.52(1.06) | -1.2(0.99) | 0.04 (1.28) |
| Upper canine width (mm) | 29.9 (1.72) | 28.18(1.08) | 29.9 (0.98) |
| Lower canine width (mm) | 26.8 (1.0) | 26.67(1.09) | 26.48 (1.14) |
You can see that I have not outlined the p values from the statistical analysis. This is because these are irrelevant when looking at the effect sizes. These differences are in the order of about 1 degree or 1mm and are not clinically significant, even though they may be statistically significant. Furthermore, if we consider that the nasal breathers group with no treatment represents average growth, it appears that the myofunctional treatment did not influence anything.
These small changes are even more relevant when considering that the overjet in the treatment group was reduced from 3.7 to 3.03mm after 13 months of treatment.
At the end of a lengthy discussion that did not address the small effect sizes, the authors concluded.
“After myofunctional treatment the treatment group showed better dentofacial growth”.
I think that the data does not support this bold conclusion.
They also pointed out that this study was subject to selection bias as they could not ethically carry out a randomised trial. They went on to state that an RCT was needed.
What did I think?
It should be no surprise to the regular readers of this blog to recognise that this study is subject to selection bias. As a result, we need to appreciate the high degree of uncertainty in the data. At this point, I would like to recap some basics of study design.
I was not sure about this definition. As a result, I found further information, this stated.
“In a non randomised trial the investigator has control over the allocation of participants to groups, but does not attempt randomisation (eg patient or physician preference)”.
“A concurrent cohort study is a follow up study that compares outcomes between participants who have received an intervention and those who have not”.
“Importantly, non-randomised studies are not designed to minimise bias and may give misleading results. As a result, non-randomised studies should only be undertaken when RCTS are unfeasible or unethical”.
As far as I am concerned, there are no ethical reasons that stop investigators from doing a trial of myofunctional treatment.
Final thoughts
Even if we accept that this study has some flaws, we cannot possibly get excited about the small effect sizes. In fact, I wonder how anyone can state that this treatment is effective when we consider that the treatment took 13 months to achieve very little.
It is great to see that some groups are carrying out studies into this interesting treatment. However, this is another study that suggests this treatment does not really do much?
Emeritus Professor of Orthodontics, University of Manchester, UK.
I think it does a lot.
It burns the pocket of families very early on in the child’s life.
It erodes the confidence of any clinician, from the parent’s perspective.
It is heavily marketed for GP’s and parents who love playing the role of orthodontists from their home computer.
It completely exhausts all compliance that the child would have in their life.
Very well said !
“Very early on in the child’s life” is precisely when a child’s optimal oral habits, chewing technique for natural tooth alignment and growth, nasal breathing, and posture should be encouraged for optimal long-range results. Therefore, proper oral habit training must be FREE and available to all children of all economic levels so that it does not “burn the pockets of families”.
This training is free and found in all wild animals in nature, and in indigenous peoples, and occurs naturally, instinctively where modern life’s incorrect habitats do not interrupt the natural methods of optimal growth. There should be more studies to document all of the natural methods which could be FREE for ALL economic levels of society.
Modern habits: remove biomechanical proprioceptive force links between hands, food and teeth by using UTENSILS.
Primitive Instincts: use BOTH HANDS to hold and control food to form biomechanical proprioceptive force links between hands, food, and erupting teeth for optimal alignment and growth.
Echo of Linder-Aronson post adenoidectomy studies. Post “change mode of breathing” very small perceived change in facial growth 5 years on,..
Did they eliminate the cause of the mouth breathing before the myofunctional treatment and if not, did the myofunctional therapy convert mouth breathers into nasal breathers (I wouldn’t see a reason why).
They did not mention the effect of any of the treatment on mouthbreathing in the paper. However, they did use Myofunctional exercises as part of the treatment.
When I read “there were no fundamental differences between the groups at the start of treatment”, and there was no effect after 13 months of treatment, then I was interested to know whether or not the mouthbreathers stopped mouthbreathing. After a quick review of the article, I could not find any note on whether treated patients actually stopped mouthbreathing. Did I miss it?
You are correct, they did not report on the effects on airway, mouthbreathing or any other outcome measures that are more relevant and interesting than cephalometric.
Excellent review, Kevin – thank you. BTW – since the study was done in China, the subjects presumably had short (anterior) cranial base morphology. The original orthodontist (Dr Earl Bergersen) who introduced this idea in the 1960s designed his devices based on a sample of Caucasian (presumptive long cranial base) children. In any case, the “commercial dilution” of his approach has not delivered promises made by various companies using a “diluted” approach – but Dr Srinivasan identifies financial reasons for its continued promotion and use.
Tell me if I understand the result of this study, there is no difference among the groups before tx. There is no difference among the group s after tx. And we do not know whether the mouth breathing patients have stopped mouth breathing after the myofunctional therapy. So, is there any positive or negative change that has been done to the patients?
Dear Dr Mui, I believe they mentioned it in the discussion and not the results:
In our study, from T1 to T2, the lower facial height of children in the MB-M group did not increase significantly. The upper anterior teeth were retroclined, the overjet reduced, and the overbite increased. There was a slight increase in the width of maxillary canines, suggesting that myofunctional treatment played a role in controlling the lower facial height and promoting the transversal development of the maxillary arch. After passive myofunctional therapy, Chuang et al. reported changes in craniofacial parameters and life quality for children with sleep apnea. They also found improvements in nasal breathing, mandible linear growth, and airway morphology [18]. Unlike our study, Chuang et al. discovered more vertical growth in the anterior facial height in the treatment group subjects, indicating the mandible clockwise rotation trend [18]. These inconsistent findings might be related to the differences in patient characteristics and methodological techniques between our study and Chuang et al’ study.
Myobrace trainer, as an oral muscular trainer, could promote the lateral development of the dental arch for kids with insufficient lateral development of the maxillary arch [37]. It has also been reported that a myobrace trainer could reduce overjet while increasing facial height for patients with ANB angle > 4° [38]. However, our research found that vertical development was controlled after mouth breathers wore myobrace trainers. The different results were probably caused by subjects with different sagittal and vertical skeletal discrepancies. In the MB-M group, the ANB angle was 1–4°, and the SN-GoGn angle was 28–37°, indicating that myofunctional treatment combined with myobrace trainer might have some control over the vertical development of mouth breathers with normal sagittal and vertical growth.
With a treatment of 13.0 ± 1.1 months, 66 children in the MB-M group had improved lip sealing and nasal breathing, consistent with those reports on the improvement of peripheral muscle functions of children with the myofunctional treatment [39,40,41].
Dr. Ahangari,
Could you please enclose a copy of your study? I was unable to find it on either Google Scholar or PubMed. Thank you very much.
John
Its a great pointing out to a study design that is clearly biased. 13 months and 1mm? pfft..