Let’s have a first look at Midfacial Skeletal Expansion (MSE).
Orthodontics may be in an expansionist phase. Recently, there has been a large amount of social media publicity about Midfacial Skeletal Expansion (MSE). I thought that this paper provided us with some initial evidence about this technique.
Orthodontic expansion is clearly an established form of treatment. There are several methods of expansion. However, Rapid Palatal Expansion is indicated when there is a marked skeletal transverse discrepancy. When RPE is provided before the palatal suture is fused, there is expansion at the suture. Nevertheless, there are also risks of tooth tipping, bone dehiscences and root resorption. This is because the RPE appliances are tooth-borne. Concern over these side effects has led to the development of bone borne expanders. One of these is the Midface Skeletal Expander.
The inventor of this technique was a co-author of this paper. He also holds the patent for the Midfacial Skeletal Expansion device jointly with Biomaterials Korea. In the introduction, they stated that this technique had been thoroughly studied. They quoted three papers to support this claim. I had a quick look at these. One article was a case report, the other two papers reported on cohorts of 15 patients. I am not sure that this is “thoroughly studied”. I shall look at this evidence in another blog in the next couple of weeks.
The authors pointed out that when we measure the effects of MSE, we should use an angular measurement system to take into account that expansion is archial.
I decided to have a good look at this paper because it dealt with a new, perhaps controversial, method of treatment.
A team from Los Angeles did this study. Progress in Orthodontics published the paper.
Ney Paredes et al. Progress in Orthodontics: https://doi.org/10.1186/s40510-020-00320-w
This paper is open access, so anyone can read it.
What did they ask?
They did this study to :
“Quantify the differential components of MSE expansion by calculating the fulcrum locations and applying a novel angular measurement system”.
What did they do?
They did a retrospective study and analysed the records of 39 successfully treated patients. All had been diagnosed with maxillary deficiency and were aged 18.2 years. Importantly, the patients had to have CBCT images taken at the start of treatment and within 3 weeks after active expansion.
They identified the maxillary deficiency using lines drawn at coronal cuts of the CBCT images. You can find details of this in the paper.
They developed a rather complicated method of measurement. Essentially, they superimposed the sequential CBCTs on the cranial base. They then identified the fulcrum of any skeletal movement. I thought that this methodology was very complicated, and to be honest, I could not understand it. Perhaps, I am getting old, but this was beyond me. They then used the traditional linear measurements and the novel angular measurement to evaluate the effects of the treatment. Finally, they ran univariate statistical tests across several pre and post-treatment variables.
What did they find?
They provided a large amount of data and statistical tests. I extracted the most relevant variables into these tables. The first is the traditional linear measurements.
|Treatment change (mm)||Means and 95% Cis|
|Zygomatic line||2.31 [1.986, 2.614].|
|Alveolar bone line||2.93 [2.5659, 3.2941]|
|Dental Line||3.84 [3.3253, 4.3547].|
They suggested that this represented 60% skeletal expansion, 16% alveolar bone bending and 23% dental tipping.
This second table is the angular measurements.
|Treatment change (degrees)||Means and 95% Cis|
|Frontozygomatic angle||2.82 [2.423, 3.177]|
|Fronto alveolar angle||2.83 [2.4534, 3.2066]|
|Frontodental angle||3.92 [2.5434, 3.2966]|
These values represent 96% skeletal, 0.3% alveolar bone bending and 0.09% dental tipping.
“MSE produced almost pure skeletal rotational movement. Importantly, alveolar bone bending and dental tipping were not statistically significant”.
“Conventional linear measurements can falsely exaggerate the alveolar and dental components of MSE treatment”.
No authors declared a conflict of interest.
What did I think?
Firstly, this is a retrospective paper, and I do not usually review these unless it raises important issues about a new technique. I felt that this was the case with this paper. We need to remember that when a study includes retrospective data, we must assume that it is subject to selection bias. Unfortunately, this is the case with this paper because all the patients were successfully treated. As a result, we do not know anything about the cases that were not successful. No one is 100% successful in all their treatment.
Nevertheless, we should not totally ignore retrospective papers. This is because they provide useful information that can be used for sample size calculation for future trials. Significantly, we should not change our practice based upon retrospective studies.
I would like to see a trial of this technique. The authors state that this is not ethical. I disagree. They could randomise to MSE and a delayed treatment group. This would not be unethical because the control group can be treated six months later. As they are not growing, there would be no harmful effects. This would be a great study.
Unfortunately, I was not too convinced about their method of measurement. I could not help thinking that a new measurement was developed to evaluate a new technique?
It was important to see that the effect sizes were relatively small. For example, they were in the order of 2mm with wide 95% confidence intervals. I am not sure that these are clinically significant and I would like to see what we can get with traditional RME. I am posting about a trial that looks at this later this month.
Finally, in writing this blog, I came across a large amount of information about this invasive technique. Consequently, I am going to have a closer look at this and post about it. Hopefully, this will help us understand this novel and exciting approach a lot more.