A new randomised trial of miniscrew supported RME
Rapid maxillary expansion (RME) is an important orthodontic treatment method. A recent development has been miniscrew supported RME. This new trial compares mini screw with tooth borne RME.
Traditionally, RME devices are placed directly onto the teeth. It has been suggested that this method does not always achieve maximum skeletal expansion because of tipping the molar teeth. Recently, bone borne expansion devices have been developed with the aim of reducing these drawbacks.
A team from Turkey did this study to compare tooth borne and bone borne RME devices. The Angle orthodontist published the paper.
Tugce Celenk-Koca et al
Angle Orthodontist: Advanced access: DOI: 10.2319/011518-42.1
What did they ask?
The asked whether there were any differences between conventional and miniscrews supported RME devices.
What did they do?
They carried out a two arm parallel randomised trial with a 1:1 allocation of interventions. The PICO was
Participants: Orthodontic patients requiring 8mm expansion with a mean age of 13.8 years (SD=1.2)
Intervention: RME supported by mini screws
Control: RME placed on the molars and premolars
Outcome: The primary outcome was correction of crossbite. The secondary outcomes were skeletal and dental measurements (including root resorption) from CBCT images taken at the start of expansion (T1) and 6 months later (T2).
They did a pre prepared randomisation and concealed the allocation using sealed envelopes. They carried out simple univariate statistics.
What did they find?
The groups were similar at the start of treatment. They randomly allocated both interventions to 21 patients in each group. Unfortunately, I could not find any data on whether the crossbites were corrected. I have extracted this data from their CBCT information and calculated the confidence intervals. I have only presented this for data collected at T2 because this provides us with sufficient information on the effect size
|Incisive foramen width||4.7||6.7||1.9 (1.19-2.6)|
|Sutural width at premolars||2.5||4.6||2.1 (1.4-2.7)|
|Sutural width at molars||2.0||3.9||1.9 (1.2-2.5)|
When they looked at the buccolingual inclination of the teeth they found:
There were no marked differences in root resorption.
The authors interpreted their findings and concluded;
“bone borne expansion increased the maxillary suture opening more than 2.5 times tooth borne expansion”.
What did I think?
I thought that this was an interesting study. Nevertheless, there were some areas that they did not clearly report. For example, the inclusion criteria was that the patients had to have maxillary restriction. I could not find any information on how they diagnosed this feature. They also did not report their primary outcome.
It was a shame that this was another paper that the Angle published that did not conform to the CONSORT guidelines for reporting of trials. I felt that this made it difficult to read and interpret. Perhaps the Editor will address this problem?
When I looked at the conclusions, I was concerned that they stated that bone borne expansion was 2.5 times the treatment effect of tooth borne expansion. Again, I could not work out how they calculated this effect. We also need to remember that expressing treatment differences in this way tends to over exaggerate the treatment effect.
However, we need to look at the effect size of the sutural expansion. This is only 2.1 mm and the CI suggests that it could just as easily be 1.4 or 2.7mm. The headline now is:
“bone borne expansion is 2.1 mm more effective than tooth borne”.
This does not sound so good. But you may think that this is clinically significant and is sufficient for you to adopt bone borne expansion. But we also need to consider whether the additional trauma and burden of care is justified by a difference in expansion of 2mm. However, this study allows us to give this information to our patients. They can then decide on their treatment method.
I am sorry to be so critical of a study that appeared to be well done, but we need to consider these issues when we interpret papers.
Emeritus Professor of Orthodontics, University of Manchester, UK.