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.
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:
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).
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.
Emeritus Professor of Orthodontics, University of Manchester, UK.