A massive Cochrane Review on treatment for crossbite.
There has been a large amount of interest and research into maxillary expansion. A multinational team has now condensed this into a Cochrane Systematic Review. I thought that the results were clinically relevant and fascinating.
Maxillary expansion is currently attracting significant interest from both the clinical and research point of view. Furthermore, orthodontists are making many claims about the risks and benefits of this treatment. As a result, this review is timely.
It is challenging to do a Cochrane review, and the authors provide a high level of research evidence. This review adds to our knowledge of crossbite correction.
A multinational team from Genoa, Italy, Rio, Brazil and Liverpool, UK did the review. The Cochrane Collaboration published it.
Alessandro Ugolini , Paola Agostino, Armando Silvestrini-Biavati, Jayne E Harrison , Klaus BSL Batista
Cochrane Database of Systematic Reviews 2021, Issue 12. Art. No.: CD000979.
What did they ask?
As with most orthodontic Cochrane Reviews, they asked a simple question;
“What are the effects of different interventions to correct posterior crossbites”?
What did they do?
The team did a very detailed systematic review of the literature. You have to carry it out to a very high standard when you do a Cochrane review. In effect, this means closely following Cochrane methodology and editorial review. As a result, Cochrane reviews tend to be of a high standard.
In this review, the PICO was
Participants: Children and adults with posterior crossbites
Interventions: Any orthodontic (not surgical) treatment used to correct posterior crossbites.
Comparison: Different types of treatment or no treatment.
Outcome: The primary outcome was the correction of the crossbite measured as a dichotomous outcome.
There were multiple secondary outcomes, for example, the amount of expansion, stability, TMD, quality of life, length, and cost of treatment.
They confined the review to randomised trials.
They did the study in several classical stages. The first was an electronic search of databases, followed by relevant hand-searching. Next, two authors screened the study abstracts, identified the final sample of papers, and extracted the appropriate data. Then they assessed bias with the Cochrane Risk of Bias tool. Finally, they did the relevant meta-analysis.
What did they find?
The team identified 31 trials. This is a large number for an orthodontic review. As a result, the authors had to present a large amount of data. I do not have the space to go into all their findings here. Nevertheless, I shall concentrate on their significant results.
The age of the patients ranged from 5-17 years old. Of these 12 studies included children aged 5-11 years old, 13 studied adolescents between 11-16 years old. The trials reported the effects of simple expansion plates, quad helix appliances, Hyrax, Tooth tissue borne expanders (Haas), Tooth-bone borne and bone borne appliances.
Eight reported the primary outcome of correction of crossbite. All the others reported that the crossbite correction was 100% successful.
When they looked at the risk of bias, they found 15 studies were at high risk of bias, 8 were low risk, and eight were unclear.
The investigators carried out eight meta-analyses. This is an open-access paper, so you can read all these when you can. I am just going to report in general terms.
Treatment vs untreated control
Removable expansion plates versus untreated control were effective. The odds ratio of correction using a removable plate was 26.2 (high strength of evidence). Furthermore, when they looked at the molar movement, the effect size was 3.3mm (moderate strength of evidence).
They found similar results for the quad helix when compared to no treatment. The odds ratio of correction was 50.59 (High certainty of evidence).
Quad helix vs removable expansion plate
The quad-helix was more effective than the expansion plate in correcting expansion with an odds ratio of 1.29 (Moderate certainty). There was a difference in the final intermolar distance with the quad helix of 1.48mm (Moderate certainty). Treatment with the quad helix was a mean of 3.15 months shorter than with the expansion plate.
When they looked at the Haas v Hyrax, there were no differences in success or amount of tooth movement.
Similarly, there was no difference between Hyrax and fixed bone-borne appliances and Hyrax vs bone-borne appliances.
The overall implications for practice from this review were:
“For children in the early mixed dentition stage (7-11 years old) using removable appliances and quad helix appliances was an effective form of treatment. The quad helix was more effective than the removable expansion plate”.
“For children and adolescents (aged 7-16 years) there may be no difference between the Haas and Hyrax”.
“For all other appliances (bone-borne and tooth-bone borne) the evidence was of low quality and insufficient to draw any conclusions”.
What did I think?
This was an extensive systematic review. The team did this using standard systematic review methodology and did the study to a high standard. The Cochrane editorial team would have had considerable input into the review. As a result, this is an excellent condensation of evidence on the correction of crossbites.
The conclusions are clinically relevant and helpful. While they reflect our clinical experience, it is good to see that trials reinforce this. Consequently, this review gives us evidence to plan treatment and inform our patients of the risks and benefits as part of consent.
This review did not wholly update us on all the clinical controversies. This was because the authors could not find any trials that looked at MSE/MARPE. Importantly, this leads me to conclude that we currently do not have strong evidence to recommend these techniques to our patients. Unless we fall back on clinical experience. There is nothing wrong with this approach. However, we need to be honest about this and do not suggest this treatment will do more than correct the crossbite.
The jury is still out on the effects of expansion on skeletal change, breathing, etc. There is an urgent need for trials into this question. These are not difficult to do. Surely, there are some researchers out there who are interested in answering this vital question.
I have previously worked on research projects with Jayne Harrison and Klaus Batista.
Emeritus Professor of Orthodontics, University of Manchester, UK.