September 27, 2021

Do orthodontic extractions change the airway? A systematic review.

One of the most controversial areas of orthodontic treatment is the effect of orthodontic extractions on the airway.  There are firm opposing views on the risk/benefit of extractions.  The argument is certainly heated.  This new systematic review may help provide us with more evidence to discuss.

I have posted extensively on the relationship between orthodontic treatment and extractions on the airway.  These posts have generated a large amount of discussion. Unfortunately, these “discussions” are based on the science and myths of orthodontic treatment.  Currently, science tells us that evidence is absent on the effect of orthodontics on the airway.  Yet, people who oppose this view tend to rely on case reports and personal experiences.

I feel that research is undoubtedly needed on this question. As a result, this systematic review may provide us with information that should be useful.

 

A team from Alberta, Cleveland and Cairo did this study. The AJO-DDO published their paper.

Pharyngeal airway dimensional changes after orthodontic treatment with premolar extractions: A systematic review with meta-analysis

Noha Orabi et al

AJO-DDO advance access.  https://doi.org/10.1016/j.ajodo.2021.03.013

 

What did they ask?

They did this study to:

“Investigate the effects of orthodontic treatment aimed at occlusal and sagittal changes on pharyngeal airway dimensions assessed through 3D CBCT imaging”.  Which is nice.

What did they do?

The authors carried out a systematic review.  The PICO was:

Population: Adult and growing orthodontic patients with any malocclusion

Intervention: Orthodontic treatment aimed at sagittal dimensions, extraction and distalisation.

Comparator: Non-extraction or no treatment.

Outcome: One year: volumetric airway changes. Two year: Hyoid bone displacement.

The authors included retrospective, prospective cohort, randomised or quasi-randomised trials.

They did a standard systematic review with electronic and relevant manual searches. First, two reviewers selected the papers and discussed any discrepancies with a third author.  Then they extracted data from the papers. Next, they assessed the risk of bias with the relevant measures. Finally, they evaluated the overall quality of the evidence using the GRADE approach.

What did they find?

After excluding studies with no control groups, unclear reporting and non-standardised timing of CBCT imaging, they included seven retrospective studies in the qualitative analysis.

When I looked at the data, I thought that the most relevant findings were:

Nasopharyngeal volume

Four studies (269 participants) showed no statistically significant change in airway volume after premolars were extracted.  The mean decrease in volume was -0.09 cm3 (95% CI -.27 to 0.10).

Oropharyngeal volume

There was a statistically significant increase after extractions.  The mean volume increased by 0.41cm3(95%CI 0.05-0.8).

There were no other statistically significant differences between the extraction and control groups for Oropharyngeal MCA, Velopharyngeal volume, Velopharyngeal MCA, Glossopharyngeal airway volume, Glossopharyngeal MCA and total pharyngeal airway volume.

Finally, the GRADE analysis showed very low certainty of evidence.

Their overall conclusion was:

“There is no strong evidence to support the concept that premolar extractions reduce the oropharyngeal volume or MCA.”.

Importantly they wrote:

“As the level of evidence was considered very low, readers should be aware that there is little confidence in the magnitude and direction of the summaries”.

What did I think?

This is an area in which opinions are divided.  I have looked carefully at their methods, and there are several issues that we need to bear in mind.  The authors pointed these out.

  • All the studies were retrospective. This fact means that the overall level of evidence is low.
  • The sample size of the included studies was small.
  • The CBCT images were taken with the patients sitting. This position may not be relevant to images taken while the patient is lying down asleep.
  • There was a general lack of standardisation of the CBCT images.

Unfortunately, these are significant limitations and illustrate the difficulty of coming to firm conclusions on this problem.

So, where does this leave us?

I have thought about this and other studies. My feeling is that we do not know if extractions influence the airway. As a result,  we cannot inform our patients that extractions will or will not influence the dimensions of their airways with any certainty.

We simply need urgent research that uses patient-relevant outcomes into this increasingly important question.  If I had my time again, I would be trying to do this research.

Finally, I cannot help entering the controversial area of some orthodontists’ claims about past extraction treatment.  Surely, it is unethical to suggest that past extractions have influenced the airway? I have no doubts that we should not be selling “extraction reversal” treatment with this claim.

Have your say!

  1. What about head posture –> how much more forward head posture was noted with the extraction group compared to control group.

    CBCT is one thing –> but actually standardizing profile photos to include full body photographs is a must to assess cants and forward head posture.

  2. This study depicts one of the flaws inherent in orthodontic research. I believe that it is universally accepted that successful mandibular propulsive therapy of any type has some positive degree (to whatever extent that is) on increasing the oropharyngeal airway. Whether it is clinically significant enough to make a difference for that patient is specific to that patient. But here’s the thing. You can’t lump all forms of treatment into one group. If the case was treated non extraction, one may or may not have employed mandibular propulsive therapy as part of the treatment regimen. If the case was treated extraction, the clinician may or may not have used mandibular propulsive mechanics. Any time you have a retrusive mandible and you posture the mandible forward, the airway must, to whatever degree, increase in size. If this change is clinically significant, as opposed to statistically significant, will vary with each case. After 40 years of moving teeth from one position to another, I agree with the findings; but they don’t tell the whole story because they only address whether or not teeth were removed and that may be only part of the intervention rendered.

    I really wish we had a better way of doing clinical research but in orthodontics it is often elusive, as the methodology used often only looks at one facet of the intervention employed. Oh well.

  3. I have always said that on controversial issues we have to look to see what Mother Nature tells us.
    What is happening with Homo sapiens sapiens in relation to its dentomaxillary structures?
    The mouths are smaller and this is coupled with congenital dental absences, the jaws are smaller and therefore the number of teeth is decreasing, as the teeth do not fit in small jaws the same nature is removing teeth from the dental arches, the Mother nature makes the extractions that we refuse to do, nature clearly shows us a path to take, but man in his pride believes he/she can do the opposite, we think that our technology and devices can have what we want.
    So the extractions do not make the mouths small, they are in fact already small and therefore the teeth do not fit and that is why extractions are required.

  4. The changes in volume were extremely small. So my comment would be..so what? What difference does it make for the patient? None as far as I can see. Interesting study though.

  5. Another ‘cart before the horse’ paper IMO – wouldn’t we be better off putting the resources into actually Doing the trials that are needed rather than conducting another systematic review or meta-analysis that concludes we need more research? As a profession, it would be great if we could 1) define the questions in order of most importance to us and our patients and 2) pool our resources to address these. This harks back to a lecture I heard in 2005 at the WOC in Paris on the idea of needing only one journal which published only the very best research – can’t recall the speakers name tho 😉

  6. Considering its been shown that surgically setting the mandible back 10mm in Class III Patients has no effect on AHI, no effect on sleep fragmentation (arousal index), and only a tiny clinically insignificant increase in RDI, I find it extremely hard to believe 1-3mm of maxillary incisor positioning changes are remotely responsible for any of the evils extraction fearmongers peddle.

    https://www.nature.com/articles/s41598-019-46166-z

  7. But the paper says this:

    In this prospective study using overnight full PSG and 3D analysis with cone beam computed tomography (CBCT), MSS with or without maxillary surgical movement for skeletal class III patients resulted in significant changes in the sleep parameters of PSG, and volumes of PAS. Symptomatic sleep parameters including the RDI, and total RERA index significantly increased (both P < 0.001; Table 1). Particularly, even though BMI showed significant decrease after surgery (P < 0.001; Table 1), there were significant increases in the RDI, and total RERA index. In all types of PAS except for the nasopharyngeal airway, there were significant decreases in the volume, and the total volume of PAS also decreased significantly (all P < 0.001; Table 1). Several correlations between the sleep parameters in PSG and the amount of mandibular setback might indicate that the larger mandibular posterior movement is, the worse sleep quality becomes. Therefore, we suggest that MSS for skeletal class III patients could worsen sleep quality by increasing RDI, and total RERA index postoperatively. For this reason, it should be emphasized that there is a need to explain the possibility of deterioration of sleep quality after MSS in patients with skeletal class III patients, particularly in patients who require large amounts of mandibular setback.

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