An occasionally irregular blog about orthodontics

Headgear does not harm the airway? A new trial

By on January 15, 2018 in Recent posts with 26 Comments
Headgear does not harm the airway? A new trial

The relationship between orthodontic treatment and the airway is an area of controversy in orthodontics. This recently published trial may provide us with some answers to this question.

One of the newly discovered benefits of orthodontic treatment is to improve children’s breathing. I have written about this previously. The basic premise that is put forwards is the protractive forces on the maxilla result in an increase in airway volume. Paradoxically, retractive forces from headgear or retraction of upper incisors restrict the tongue and/or airway. This then causes sleep disordered breathing and other problems. While this area is clearly important. There have been no clinical trials into this “pathology” and most of the evidence is at the level of case report and personal opinion.

In many ways, we may have lost opportunities to study this question. For example, the investigators in the “classic” early Class II treatment studies did not evaluate the airway. When we designed our study, we did not even consider that treatment would influence the airway. This is probably because this problem had not been identified in orthodontic patients.

I was, therefore, very interested to see this new study. This looked at the effect of cervical pull headgear on the skeletal pattern and the airway.

A team from Oulu, Finland did this trial. The EJO published the paper.

Airway and hard tissue dimensions in children treated with early and later timed cervical headgear—a randomized controlled trial

Johanna Julku, Kirsi Pirilä-Parkkinen, and Pertti Pirttiniemi

European Journal of Orthodontics, doi:10.1093/ejo/cjx088

They asked whether

“The timing of cervical headgear treatment had an effect on pharyngeal airway dimensions”.

What did they do?

They did a parallel group controlled trial with a 1:1 allocation. The PICO was:

Participants: 7 year old children with Class II occlusion with overjets greater than 6mm and a deep bite. The investigators identified the children from a school screening programme.

Intervention: Standard cervical pull headgear when the patients were approximately 7 years old. This was the early treatment group.

Comparison: No active treatment. They observed this group for 18 months. After this time they treated them with cervical pull headgear. This was the later treatment group.

Outcome: Cephalometric analysis of hard tissues and airway dimensions. They collected this data at the start of treament (T0), after early headgear treatment/observation (T1) and when all the treatment was completed (T2).

The sample size calculation was fairly clear. Unfortunately,  I was not clear on the effect size that they used.

They used a pre-prepared randomisation, allocation and concealment were done using sealed envelopes. They could not blind the operators and patients to the intervention. Nevertheless, the ceph analysis was blinded.

What did they find?

They randomised 67 children to the early and later treatment groups. Seven of the early treatment group and 4 of the later group did not complete the study. They did not do an Intention to Treat analysis.

They presented their data in two massive cephalometric tables and analysed many variables. We need to be careful when we interpret this data because of the risk of finding statistical significance by chance because of the testing of multiple related variables.

I do not have the space to go through all the variables that they measured. However, in summary, they found the following

1          There was greater posterior movement of the maxilla in the early treatment patients. The mean difference between the early and later treatment groups for SNA was 1.2 degrees. They reported similar effects for ANB. These are small differences and I am not sure that they are clinically significant.

2          When they looked at the pharyngeal measurements, they did not find an effect of the headgear treatment.

They concluded

1          Cervical pull headgear effectively corrected Class II malocclusion

2          The headgear treatment did not have an effect on airway dimensions.

What did I think?

This was a well carried out and very ambitious trial. The authors reported it well and wrote a clear discussion on their findings.

As with all studies, there are problems.  We need to look at these closely so that we can decide on how confident we are with the studies findings.

The first, and most important, issue is the choice of cephalometric measurement as an outcome measure. This, of course, means that they could only measure the airway in two dimensions. As a result, many clinicians may not accept these findings. However, when they started the study, I am sure that CBCT imaging would expose the children to high levels of radiation and I am not sure that this would be justified.

The other issue is that they did not measure nasopharyngeal airflow as this is the most relevant outcome measure. Again, I think that this would be too resource intensive for this study.

Another important point that we need to consider is that the amount of “retraction” of the maxilla was small. I cannot see how this would have an effect on the airway.


I have thought about this carefully and I think that we should accept that this study is the best that we can get.  It is certainly better than the current “evidence” that is based on a few case reports and personal opinion.

In summary, I feel that this paper adds to our knowledge. It is interesting that the findings do not support the current opinions and perceptions of those who are suggesting that retractive mechanics compromises the airway. This study also provides a model for future studies that should be carried out. Perhaps the myofunctional practitioners and the orthodontic physicians should get on with doing a study? Until then this is the best that we have got.

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  1. Peter Doyle says:

    Anything that distslises or entraps the mandible is bad news for the patient . Lost opportunity for mandibular advancement is also poor treatment IMHO.
    When is some going to post operatively follow up a retraction treatment group for migraine incidence ,canine eminence loss , mandibular distalisation (clicks) , poor cervical neck posture , and premature facial ageing , as excess facial tissue prematurely losses its elasticity around the mouth due to lack of hard tissue support (teeth) in the patients 30’s. The patient then develops atypical facial pain in their 40,s.
    Agree with your last comment , the myofunctional people need more scientific ammunition. Airway is only one of the clinical issues with traditional headgear.

  2. The static position of an airway while awake is not correlative to an airway when a person is asleep. If the author was aware of this the study would never been done as it is working off of a false premise to begin with. There are also other variables that are not taken into account, such as resting tongue position, Mallampati, palatal vault height, etc. that also impact overall intraoral volume.

    One cannot make a statement about a child and then extrapolate to 20+ years later when so many patients that have had serial extraction and retraction end up in my office for airway therapy. If there was no cause and effect why is there such a high percentage of OSA patients missing bicuspids? It seems that this is an oversimplified study presenting a conclusion from just a small amount of information working off of a false premise.

    Before a study like this is done, the author might become more knowledgeable about Sleep Disordered Breathing.

    • Lysle Johnston says:

      Post hoc ergo propter hoc, a classic logical fallacy. Such reasoning is to be expected whenever Kevin’s blog sounds a dog whistle for strange ideation and faulty science.

  3. Mohammad says:

    As you mentioned, not using CBCT is an important issue. So controversy still is a problem.
    And I should thank you so much for sharing all these useful Information.

  4. Fenris Ulfr says:

    But Kevin! There you go again using “facts” and “research” instead of “belief” and “opinion”.

    According to the alternative facts below, you are wrong.

    If there is no cause & effect relationship, why do so many patients with cardiac disease also have amalgam restorations? Why do 94.56% of female patients who had orthodontic treatment in the past eventually become pregnant several years later? They end up in my office, and must be representative of all patients world-wide (of course!)

    Do we really need research to prove unmistakable connections such as these?

    As acolytes of the flat earth society and disciples of the pyramid of denial, we simply must not let facts interfere with our deeply held beliefs. We mavericks and free-thinkers are not fettered by biological and logical implausibility…instead it spurs us on to even more specious claims and spurious therapies. Join us, and drop the burden of rational thought!

  5. Interesting study… Some thoughts: Headgear (Facebow) treatment involves the use of two bands on the upper first molars. The result of such therapy can be described by this possible outcomes:
    1. No change, if the patient uses the headgear less than 8 hours a day, no interdental spaces develop, and you can’t see any variations in cephalometric analyses. Any improvement in the first molar relationship could be attributed to mesial drifting of the lower molar or some forward mandibular growth, while the upper first molar is being held in position by the headgear.
    2. If the headgear is used for approximately 14 hours, you will see some distal movement of the upper first molars in a cephalometic x-Ray, some interdental spaces occur (about a 1/6th of a millimeter per month or 1 millimeter every 6 months).
    3. If the headgear is worn 24 hours a day (now a days, very rare to see this kind of cooperation), the upper molar will distalize about 1 millimeter per month, which is about the same that happens when forces are applied 24 hours a day on a tooth with a bracket.
    The changes in ANB may be due to remodeling in the upper incisor area being retracted by the interdental fibers (if the molar has moved distally), and some mandibular growth. In this case, this cephalometric measurements may be deceptive.
    On airways: I believe I have never seen a maxillary bone move backwards, except with a maxillary surgical setback. Most of the effect of a headgear is in holding the current position of the upper molar or its effective distalization.
    If we observe a lateral cephalogram, the maxilla, at it’s horizontal position, is at the widest part of the airway (except if we have adenoidal tissue reducing the space, which is transitory by nature). I believe we can hinder horizontal growth when used over 14 hours or more, but I don’t believe we can actually distalize the maxillary bone and reduce airway space. The mandible may be a factor in reduced airway space, but it was not the scope of this study. A thought: I’ve had thoughts about the accuracy of airway images in lateral cephalograms and CBCT’s… If the patient swallows during the taking of the x-Ray, the AP position of the head/neck… Also, airway problems really become a problem while sleeping, not with the patient in standing position. There are other many factors to analyze. Food for thought.

  6. As you say, Kevin, the analysis was done in 2D and so does not represent the functional morphology of the upper airway. There are numerous studies showing that 2D cephs have little correlation with 3D data, and that cephalometric analysis is not mathematically based (e.g. Moyers and Bookstein). The claim that CBCT scans would be involve “high levels of radiation” is a little far-fetched IMHO. The studies on the pediatric airway by Schendel et al., and others were done using 3D CBCT scans. One of the most important findings IMHO in those studies is that the pediatric airway shows a plateau in terms of growth and development during the age group studied in the article that you discuss above. This developmental behavior might, at least in part, explain why little or no differences were found. Finally, there are other studies that go beyond personal opinion and case reports (e.g. Singh and Hodge).

    Best wishes for 2018 –

    Moyers RE, Bookstein FL (1979) The inappropriateness of conventional cephalometrics. Am J Orthod., 75: 599-617.
    Bookstein FL (2015) Reconsidering “The inappropriateness of conventional cephalometrics”. Am J Orthod Dentofacial Orthop 149: 784-797.
    Schendel SA, Jacobson R, Khalessi S (2012) Airway growth and development: a computerized 3-dimensional analysis. J Oral Maxillofac Surg 70: 2174-2183.
    Singh GD and Hodge MR. Bimaxillary morphometry in patients with Class II division 1 malocclusion treated with Twin Block appliances. Angle Orthod. 72(5), 402–409, 2002

  7. Diana Batoon, DMD says:

    While I completely agree that there needs to be more scientific research in this area, open minds and the willingness to change the way we have always thought in dentistry and orthodontics would help facilitate the pathway.

  8. Fenris Ulfr says:

    The study cited “Bimaxillary Morphometry of Patients with Class II Division 1 Malocclusion Treated with Twin Block Appliances” is a retrospective study with no control group. Thus, the influence of growth remains unaccounted for, with regard to the pre and post-Tx differences. The other issue is one of measurement. Not very clear if inter-examiner reliability was calculated. Results of the linear analysis actually indicated an increase in antero-posterior midfacial distances in all groups. While WinEDMA did indicate some decrease in mid-facial distance, the methodological validity and reliability of WinEDMA has not been adequately established or addressed. The article by McIntyre and Mossey (PMID: 12831212) provides more information.

  9. Interesting as the survey is, it makes me wonder about a few things that have nothing to do with the airway analysis –

    1 For the ceph analysis to really be blind there would have to be attachments – likely bands – on the molars in the non-treatment group. Was that the case? These kids wore intra oral bands that didn’t do anything?

    2 I am more usually interested in molar correction, or canine correction than a reduction in ANB or SNA, but I guess it depends on the defintions used before you can conclude that headgear age at 7 effectively corrects class II malocclusion. I wouldn’t consider a 1.2 degree improvement in SNA for an 8 year old to be reassurance that they’re class I but I haven’t tried this kind of treatment or followed them up to adult dentition.

    3 If headgear at age 7 actually does correct class II malocclusion – do many people do it? I know I don’t, and I don’t know anyone that does. Is it popular? Have I missed something? I would have thought there are too many things still to happen after age 7 to make this kind of call.

    Stephen Murray
    Swords Orthodontics

  10. Here’s what I don’t understand about headgear….why do we think that a jaw that is so undergrown as to not have enough room for the teeth (ie: crowding or protrusion) should be inhibited from growing further? Isn’t it already stunted enough?

    Here’s what I don’t understand about this study….if you have two groups that already have maxillary jaws that are undergrown and you apply further restriction to their growth, why WOULD there be any difference between the two?

    Last stupid question…If you study two groups that already have craniofacial risk factors for airway dysfunction (ie: narrow palate, retrognathic mandible) and you try to make the problem worse, what exactly are we trying to prove? That a headgear doesn’t make the problem worse?

    OK…one more silly thing….why don’t we study ways to make the airway BETTER and stop defending constructs that were developed without ANY concern for breathing, sleep or overall health. (BTW, Kevin, we have an IRB already in place and we’re moving ahead to find positive solutions to a world-wide scourge.) Hint: the study is going to look at ways to reverse growth stunting and help them grow to what genetics (per anthropologic standards) predicts they should be.

    • Peter Doyle says:

      Agree and Well said. This study sets out to defend a treatment option that has been suspected clinically of many other adverse post operative symptoms. A “we found no negative impact “does not convince me with it as a treatment .

  11. Fenris Ulfr says:

    Who says the maxilla is “undergrown” and relative to what? Where does it say that the palate is narrow? Does creating 13 mm of overjet and iatrogenic bimaxillary protrusion “reverse” growth stunting and help subjects grow to their atavistic potential? Is the goal to reanimate homunculus?

  12. Fenris Ulfr says:

    That’s great to hear. Please share your findings about making the airway better once it has been published. In the meantime, as has been repeatedly and conclusively proven, headgear and extractions are great treatment modalities and should be continued.

  13. Fenris Ulfr says:

    “Suspected clinically of many other adverse post operative symptoms” – By who and on what basis? Or is this just more resistance to well-done science that does not support some of these fringe opinions?

  14. Carlos Flores-Mir says:

    Lateral cephalometry or CBCT imaging provide only snapshots of a specific moment in the respiratory cycle. Hence any measurement obtained from them is questionable. Eventually we should be able to measure dynamic imaging. The larger the sample the more representative it maybe as there would be a “tendency to the mean” effect. In any event the upper airway includes also nasal and other maxillofacial structures (several sinuses, nose, etc). We seem to centre our discussion on the oropharynx and nasopharynx but not on the other areas that are extremely more complex and equally able to suffer an obstruction. Also any discussion about breathing should include a physician assessing the function. We are not legally qualified to make such statements.
    This manuscript, as any other manuscript, had a specific question to be answered. Our discussion should be about the fact that the question could or not have been answered in a better way. I believe that those that question everything that is publish should publish data. It is not easy to publish. No study is ever perfect but some level of evidence is better that no evidence at all. We all have personal opinions but all are theoretically equal. We seem to diverge into extremes from never to always do something. If middle age have given me anything is the wisdom to see that live is never black or whit but a shade of grey. Therefore I suggest that the truth is somewhere in between. Just my grain of salt.

  15. Just to put a different perspective on everything —why are folks still using head gear at all ?Wrong force level ,wrong force vector and v.poor compliance ??? As a classics scholar in my catholic high school days,I really enjoyed the Latin discussion .Dont watch TV but I may ,now ,make exceptions for old episodes of West Wing.

  16. Hi Carlos: I love it when you say “I believe that those that question everything that is publish(ed) should publish data. It is not easy to publish”. I could not find any studies by Dr Fenris Ulfr in the medical, dental or orthodontic literature.

  17. Fenris Ulfr says:

    According to Dr. Singh, the DNA appliance is a new way to achieve natural jaw development and airway remodeling through craniofacial enhancement.
    This new technique has wide-ranging and thoroughly non-invasive applications in the treatment of sleep apnea, cosmetic dentistry, tooth-grinding and headaches, and crooked teeth related to narrow jaws and improper jaw position.

    However, I could not find no studies in the medical, dental or orthodontic literature supporting these claims of the DNA appliance as proposed by Dr. Singh. What journal might I find this information in?

    • Singh GD. Kraver M, Chernyshev O. Restoration of sleep using a novel biomimetic protocol for adult OSA: Clinical case report. CRANIO, 2018 (in press).
      Singh GD, Cress SE. Biomimetic oral appliance therapy in adults with mild to moderate obstructive sleep apnea using combined maxillo-mandibular correction. J Sleep Disord Mang 3:014, 3(1), 1-7, 2017.
      Singh GD and Kim KY. Facial enhancement using biomimetic oral appliance therapy in adults. Dent Oral Craniofac Res 2(4):313-317, 2016.
      Heit T, Sebastian J, Singh GD. A novel combined protocol for the resolution of severe obstructive sleep apnea. J Sleep Disord Ther 5(5), 251-254, 2016.
      Jung SC, Singh GD, Resolution of chronic rhino-sinusitis using biomimetic oral appliance therapy. Open J Clin Med Case Rep. 2(4):1082, 2016.
      Singh GD, Griffin TM, Cress SE. Biomimetic oral appliance therapy in adults with severe obstructive sleep apnea. J Sleep Disord Ther 5(1); 1-5, 2016.
      Singh GD, Heit T, Preble D, Chandrashekhar R. Changes in 3D nasal cavity volume after biomimetic oral appliance therapy in adults. Cranio 34(1):6-12, 2016.
      Liao F, Singh GD. Resolution of Sleep Bruxism using Biomimetic Oral Appliance Therapy: A Case Report. J Sleep Disord Ther 4: 204. 2015.
      Singh GD, Griffin TM, Chandrashekhar R. Biomimetic oral appliance therapy in adults with mild to moderate obstructive sleep apnea. Aust J Sleep Dis, 1(1);5, 2014.
      Singh GD and Chapman DC. Craniofacial changes after combined atlas-orthogonal and biomimetic oral appliance therapy. Annals Vert Sub Res. 4, 112-118, 2014.
      Singh GD, Heit T, Preble D. Changes in 3D midfacial parameters after biomimetic oral appliance therapy in adults. J Ind Orthod Soc. 48(2), 104-108, 2014.
      Singh GD and Cress SE. Craniofacial Enhancement using a Biomimetic Oral Appliance: Case Report. Dent Today, 329(12):92-92, 2013.
      Chapman DC and Singh GD. Combined effect of a biomimetic oral appliance and atlas orthogonist cervical adjustment on leg lengths in adults. Annals Vert Sub Res. 46-50, 2013.
      Singh GD and Callister JD. Use of a maxillary oral appliance for the resolution of obstructive sleep apnea. J Cranio Sleep Prac. 31(3):171-179, 2013.
      Singh GD, Ataii P. Combined DNA applianceTM and InvisalignTM therapy without interproximal reduction: A preliminary case series. J Clin Case Rep. 3(5), 2013.
      Harris WG, Singh GD. Resolution of ‘gummy smile’ and anterior open bite using the DNA applianceTM: Case Report. J Amer Orthod. Soc. 13(4):30-34, 2013.
      Singh GD, Cress SE. Case presentation: Effect of full mouth rehabilitation and oral appliance therapy on obstructive sleep apnea. Dialogue, 2, 18-20, 2013.
      Utama J, Singh GD. Effect of the DNA applianceTM on migraine headache: Case report. Int J. Orthod. 24(1); 45-49, 2013.
      Singh GD, Wendling S, Chandrashekhar R. Midfacial development in adult obstructive sleep apnea. Dent. Today, 30(7), 124-127, 2011.
      Singh GD, Lipka G. Case Report: Introducing the Wireframe DNA applianceTM. J Am Acad Gnathol Orthop. 26(4); 8-11, 2009.

  18. Conference Papers Published (Abstracts)

    Singh GD. Restoration of sleep quality using a novel biomimetic protocol for the resolution of obstructive sleep spnea. Am J Respir Crit Care Med 2017;195:A2577
    Singh GD. Pediatric epigenetics for systemic conditions associated with obstructive sleep apnea. J Sleep Disord Ther. 5(6): 20, 2016.
    Singh GD, Liao F. Effects of biomimetic oral appliance therapy in adults with obstructive sleep apnea. J Sleep Disord Ther. 5(6): 25, 2016.
    Cortes M, Wallace-Nadolski ME, Singh G. Upper airway remodeling as a treatment for obstructive sleep apnea in adults with craniofacial deficiencies. SLEEP 39 Supplement; A142, 2016.
    Wallace-Nadolski ME, Cortes M, Singh G. Non-surgical upper airway remodeling as a treatment for obstructive sleep apnea. SLEEP 39 Supplement; A139, 2016.
    Liao F, Singh GD. Effects of Biomimetic Oral Appliance Therapy on Epworth Scores in Adults with Obstructive Sleep Apnea. J Dent Sleep Med. 3(3), 98, 2016.
    Singh GD, Griffin TM. Effect of biomimetic oral appliance therapy in adults with OSA. J Sleep Disord Ther. 4(4): 58, 2015.
    Singh GD. Effect of biomimetic oral appliance therapy in adults with OSA. J Sleep Disord Ther. 4(4): 51, 2015.
    Griffin TM, Singh GD. Effects of a non-mandibular advancement device in adults with severe obstructive sleep apnea. J Dent Sleep Med. 2(3), 129-130. 2015.
    Cress SE, Singh GD. Effects of combined maxillo-mandibular oral appliance therapy in adults with severe OSA. J Amer Dent Sleep Med. 2(3), 137, 2015.
    Singh GD, Cress S. Effects of combined maxillo-mandibular oral appliance therapy in adults with mild to moderate OSA. SLEEP 38 Supplement; A194-195, 2015.
    Singh G, Griffin TM, Chandrashekhar R. Effect of a biomimetic oral appliance in adults with obstructive sleep apnea. World Association of Sleep Medicine, 2015.
    Singh GD, Heit T, Preble D, Chandrashekhar R. Changes in 3D nasal volume after biomimetic oral appliance therapy in adults. Sleep (Abstract Suppl.) 37: A150, 2014.
    Singh GD. Changes in 3D nasal volume after biomimetic oral appliance therapy in adults. Oral Health and Dental Manag. 13(2): 27, 2014.
    Singh GD, Heit T, Preble D. Changes in 3D midfacial parameters after biomimetic oral appliance therapy in adults. J Amer Acad Dent Sleep Med. 17: 889-890, 2013.
    Singh D, Heit T, Preble D. Changes in 3D maxillary parameters after DNA appliancetm therapy in adults. Oral Health and Dental Manag. 3(2): 27, 2013.

  19. Fenris Ulfr says:

    Since the issue at contention is the DNA appliance, I will restrict the discussion to the (lack of) data surrounding it instead of all the other red herrings. Appears like all the literature on the DNA appliance is of rather low quality and in the form of case reports/series with no controls or any of the other prerequisites that would confer scientific validity. Poor quality data such as this does nothing to corroborate these rather far-fetched claims. At this stage, and based on the repeated obfuscations, it is only fair to conclude that either A- It does not work like the proponents claim, or B – The proponents are more interested in sales than proving efficacy. Time to prove these claims or stop making them.

  20. So the mythical, scandinavian she-wolf speaks again? Last time she asked “However, I could not find no studies in the medical, dental or orthodontic literature supporting these claims of the DNA appliance as proposed by Dr. Singh. What journal might I find this information in?” Now given the peer-reviewed, published literature proving that she was completely wrong, she decides that she knows better than everyone else in the entire, international orthodontic profession and gives the expected cheap shot reply. I have been warded three international prizes for this work. My students/residents have followed suit. Talk is cheap. As so eloquently put by Dr Carlos, “I believe that those that question everything that is published should publish data. It is not easy to publish”. I could not find any studies by “Dr Fenris Ulfr” in the medical, dental or orthodontic literature. Perhaps she doesn’t have the courage of her convictions to stop using a pseudonym?

  21. Fenris Ulfr says:

    Chimerical claims can only be adequately addressed by lupine mythology. Dr. Singh must be quite familiar with such responses given the nature of the claims he makes. If the DNA appliance can correct ” the misalignment of body-posture, correct TMD, OSA, hypertension etc.” is it so far-fetched that a wolf could knowledgeably critique these claims?

    And the so-called ” peer-reviewed, published literature” posted so kindly by Dr. Singh? This yet again proves exactly why nobody with a scintilla of scientific knowledge would give credence to these specious dissimulations.

    But we are not that different, Dr. Singh and I. Much like him, I too have received multiple awards for creative fiction, which is why the pseudonym is required when debating such hot topics. We both eagerly await the day when one just has to make claims without the pesky burden of actually proving them.

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