It is about time that I posted about a trial. This new study looked at the effects of bone anchored RME appliances on the airway. I thought that it was great.

The original RME devices were tooth borne and this resulted in the forces being applied to the maxilla via the teeth. A recent development has been the use of mini implants in the palate to anchor RME appliances. The force is applied directly to the maxillary bones. In theory, this reduces the effects of dental and alveolar bone tipping. This means that these new devices may have a greater skeletal effect and achieve greater airway change than tooth borne RME appliances.

vervolg: Kevin O'Brien: Bone anchored RME increases nasal airflow: A good randomised trial!


A team from Orebro, Sweden and Homburg, Germany did this study. The EJO published it.

Effects on nasal airflow and resistance using two different RME appliances: a randomized controlled trial

Farhan Bazargani , Anders Magnuson and Björn Ludwig

European Journal of Orthodontics, 2017, 1–4 doi:10.1093/ejo/cjx081

Unfortunately, this paper is behind the EJO paywall and only members of the EOS can get easy access to it.  I wonder if they could think about making this open access?

What did they ask?

They did a simple study to ask a simple question;

“Does the use of a tooth borne RME (TB) or tooth-bone-borne RME (TBB) influence nasal airflow and nasal resistance in growing children with a constricted maxilla?”

What did they do?

They did a randomised controlled trial. The PICO was

Participants: 40 children aged 8-13 with uni or bilateral cross bite with a constricted maxilla

Intervention:  A tooth borne RME device (TB)

Comparison: A tooth-bone borne RME (TBB)

Outcome: Rhinomanometric measured nasal airflow and nasal resistance before and after expansion.  They also measured dental movement.

I thought that it was great to see that they did not get bogged down in a cephalometric and airway volume festival with multiple testing in the endless search for significance. Instead, they simply measure the effect of the treatment on nasal airflow etc.  This is a good outcome measure as it is what counts and is relevant to the patients.

I thought that randomisation and allocation concealment was good. They recorded all the data blind including the airflow data. The statistical analysis was appropriate

What did they find?

They completed the trial and recruited 40 participants. Unfortunately, 4 of the TB and 6 of the TBB did not complete the study.  This resulted in the numbers of drop outs in the two groups being unequal and means that there is some bias in the study.  The authors addressed this, to a degree,  by imputing data for the drop outs.

Their findings were clinically relevant.  In brief, they found that there were no difference between the groups at the start of treatment. After expansion there was higher nasal flow in the TBB group with a mean difference of 51.0 cm3/s (95% CI 9.6-92.5). Similarly, there was a greater reduction in nasal airway resistance for the TBB group with a mean difference of -0.21 Pa s/sm3.

In summary, they did not find any differences in the dental movements. However, the TBB RME resulted in a significantly increased nasal airflow and decreased nasal resistance.

They pointed out that amount of decrease in nasal resistance was equivalent to the decongestive effect of a nose spray.  As a result, this is clinically significant.

Finally, in their discussion, they felt that the TBB was more effective because the forces were delivered directly to the maxilla and not via the teeth.

Their conclusion was;

“When it comes to treating patients with constricted maxilla and upper airway obstruction, it might be wise to use the TBB RME instead of the conventional design. This could be more beneficial to the patient”.

What did I think?

I thought that this was an interesting study. The authors carried it out well and they reported it very clearly.  They also dealt with the issue of “drop outs” using acceptable methods.  It was also good to see that they addressed clinical and statistical significance.

This study adds to the data on the effectiveness of RME on the nasal airway. It certainly appears that the use of bone anchored RME is clinically effective.

However, before the “orthodontic airway physicians” and myofunctional orthodontists get too excited. We need to remember that this was a skeletally anchored RME device.  We still know nothing about removable, semi-fixed or other magical devices.



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