New evidence from a trial of Orthodontic Expansion and Sleep Apnoea in Teenagers.

Studies on sleep-disordered breathing and orthodontics are coming thick and fast. This new trial was notable for examining the effect of expansion on obstructive sleep apnoea in teenagers at the post-pubertal growth stage. Importantly, this was not another retrospective study in which the authors made exaggerated claims about the effects of their orthodontic treatment on breathing. 

The study was done by a team based in Erciyes University, Turkey. The European Journal of Orthodontics published the paper. 

What did they ask?

They did this study to 

“Evaluate and compare the effects of different RPE appliance designs on sleep-related breathing, nasal airway resistance, and dental-skeletal outcomes in post-pubertal adolescents with maxillary constriction.”

What did they do?

They carried out a randomised controlled trial with 3 arms with a 1:1:1 allocation.  The PICO was

Participants

Orthodontic patients aged 14 to 17 years in the post-pubertal growth stage. They had mouth breathing, which was confirmed through a comprehensive ENT examination. They had skeletal maxillary constriction of between 4 and 10 mm transverse deficiency with unilateral or bilateral posterior crossbites. 

Intervention one. 

This was a full-coverage RPE appliance which covered all the buccal, palatal, and occlusal surfaces of the maxillary teeth. (FCRPE)

Intervention two.

A similar RPE appliance , however, the upper incisors and canines were not included in the appliance. (MMRPE)

Intervention three.

A MARPE appliance fixed with two palatally placed mini screws. (MARPE).

Outcomes

These included;

• Respiratory polygraphy
• Rhinomanometry
• Sleep questionnaires
• PA radiographs
• Digital models

They took measurements before treatment and approximately three months after treatment.

They used a pre-prepared randomisation scheme and conducted an adequate sample size calculation. I was unclear about their method of concealment. 

They carried out a relevant univariate statistical analysis.

They compared the active treatment groups with an untreated control group. This group comprised healthy people from the same age group who attended the department. However, little additional detail about this group was provided.

What did they find?

45 patients entered the study. At the end of treatment, forty-three completed the study. Fifteen participants were enrolled in the control group, and all 15 had data collected at the second data collection.

They produced a large amount of data, and I’m going to focus on AHI, oxygen desaturation and sleepiness scale.

There were no differences between the groups at the start of treatment. Importantly, the control group had lower AHI and fewer oxygen desaturations.

I have tried to interpret the large amount of data they included by focusing on the end-of-treatment values. This is a simple yet relevant method for analysing large data sets in a study such as this. I have included data on AHI, De SPO2 and the Epworth Sleepiness Scale (ESS).

	FCRPE		MMRPE		MARPE		Control
	T0	T1	T0	T1	T0	T1	T0	T1
AHI	3.8 (1.1)	1.3 (0.6)	3.4 (0.6)	1.2 (0.5)	3.8 (0.7)	0.9 (0.3)	1.2 (0.5)	1.1 (0.5)
De SPO2	3.5 (2.6)	1.6 (1.2)	2.8 (0.8)	1.1 (0.6)	2.9 (1.1)	0.8 (0.5)	1.2 (0.5)	1.1 (0.4)
ESS	7.1 (2.6)	6.5 (2.2)	7.0 (3)	7.3 (2.9)	7.1 (2.1)	6.4 (2.5)	5.9 (1.8)	6.1 (1.8)

The statistical analysis revealed the following:

• The control group had significantly lower AHI values and De SP02 index.
• When they looked at the data for the RPE groups, they showed decreases in AHI and De SPO2 across all groups. Importantly, there was no change in the control group.
• Although AHI values decreased in the MMRPE group, the effect was not as pronounced as in the MARPE group.
• There were no significant differences in EES scores between the groups.

Their overall conclusion was

“RPE decreases AHI. This approaches the values of individuals in the control group.”

What did I think?

This was another small-scale randomised controlled trial exploring an important question. The authors noted that since the participants were post-pubertal, facial growth likely had minimal impact. Therefore, any observed changes could probably be attributed to the expansion itself. However, factors like BMI and hormonal changes during late puberty might influence tissue remodelling around the airway. This highlights the need for an untreated control group to draw more definitive conclusions. Additionally, the follow-up period was quite short.

It’s worth mentioning that the AHI values in this study for all the groups suggest mild obstructive sleep apnea, and the EES scores indicate normal levels.

We should also remember that polysomnography is considered the gold standard for sleep assessment. In this case, the authors used respiratory polygraphy, which is more practical but generally less sensitive than PSG. Still, it offers reasonable validity for measuring AHI, though it’s a bit of a compromise.

The study also found that MARPE was the most effective method of expansion, adding to the evidence supporting the use of miniscrews in expansion devices.

It was encouraging to see that the authors avoided making exaggerated claims about expansion treatment. Overall, this study is much better than the retrospective, convenience-based studies often promoted by some “airway” orthodontists.

We’re gradually making progress in exploring this important area of research.