3D assessment of Carriere Motion 3D appliance
We are now seeing more papers on the Carriere Motion appliance. This sectional fixed appliance provides a Class II force to correct buccal segment relationships. There has not been much research on this treatment method, and this new paper adds to our knowledge.
I have posted about this treatment method several times. In these posts, I have been critical of the claims made by the inventor and Henry Schein Orthodontics. This is because there is no evidence to support the following claims that they make.
- The appliance distalises the upper buccal segments.
- Treatment encourages forward positioning of the mandible
- It shortens treatment time by 3-6 months.
- It increases the airway volume.
Over the past few years, several research projects have been into the Carriere Motion. I have posted about them before. My overall feeling about these papers is that they outline early steps in research. They suggest that the main effects of this appliance are not very different from Class II elastics or functional appliance.
A well-known team from Michigan, USA, did this new study. The AJO-DDO published the paper.
Elizabeth V. Biggs, Erika Benavides, James A. McNamara, Jr, Lucia H. S. Cevidanes, Flavio Copello, Ronald R. Lints, Joel P. Lints, and Antonio C. O. Ruellas,
AJO-DDO online: https://doi.org/10.1016/j.ajodo.2023.05.031
All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest; none were reported.
What did they ask?
They did this study to:
“Quantify the outcomes of adolescent patients with Class II malocclusion treated with the Carriere Motion 3D appliance combined with fixed appliances”.
What did they do?
They did a retrospective case series study without a control. As a result, they measured the effects of the appliance and normal dentofacial growth.
The team collected the records of 28 patients who had completed their orthodontic treatment in one private office.
The main inclusion criteria were that the patients had a Class II malocclusion, completed treatment, and had full records.
They collected scans of the patient’s teeth and CBCT images taken at the start and end of the Carriere treatment and when it was completed with fixed appliances.
The team recorded and analysed many measurements with simple univariate tests across many variables.
What did they find?
They evaluated the 28 sets of records and excluded six of them for having a missing scan, the duration of treatment with the Carriere exceeded 12 months, and technical issues with data. This was an exclusion rate of 21%.
The mean age of the patients at the start of treatment was 13.5 (SD=1.6) years. At T1, this was 14.1 (SD=0.2) years; at T3, the mean age was 15.6 (SD=0.5). The mean duration of treatment with the CMA was 7.3 (SD=2.4) months; at the end of all therapy, this was 26 (SD=6.8) months.
The clinicians had taken CBCTs at the start of treatment (T1), at the end of the Carriere treatment (T2) and at the end of all treatment (T3).
They provided a large amount of very detailed data with multiple statistical tests. As usual, when I see a paper like this, I concentrate on what I feel is the most important outcome data.
These were the relevant skeletal measurements. I have included the means and standard deviations in brackets.
|SNA||82.0 (4.3)||81.8 (4.3)||81.7 (4.4)|
|SNB||78.3 (4.2)||78.1 (4.0)||78.3 (4.3)|
|ANB||4.1 (1.5)||3.9 (1.5)||3.5 (1.4)|
|SnGoGN||27.9 (3.3)||28 (3.1)||27.9 (3.4)|
There was also a large amount of data on tooth movement, which I found difficult to interpret. I hope that I have extracted the main points here.
“The upper molar derotated by -5.1 degrees during CMA treatment. Some of this was lost during fixed appliance treatment making the average -3.5 degrees.”
“The maxillary molar distalised -0.9mm during CMA treatment and rebounded during FA treatment to 0.1mm”.
“The upper incisor was proclined at 2.1 degrees by the CMA and further proclined during the FA phase to a total of 7.3 degrees. Similarly, the lower incisors were proclined 3.7 degrees by the CMA, and this was increased to 8 degrees following the FA treatment. In effect, the therapy flared the upper and lower incisors”.
I could not find any data on airway measurement or information on the overall quality of the treatment result.
What did I think?
Seeing more research into this treatment method and philosophy was good. However, we must consider that this traditional retrospective study has the following issues.
- There was marked selection bias. This was particularly characterised by the high exclusion rate of cases. This is of more concern when we consider that some cases were excluded because they took too long. This is similar to excluding patients from a medical clinical trial because they were not “getting better”. I am surprised that the AJO referees did not pick this up.
- The team presented a lot of data subjected to multiple selective statistical analyses. This means that there is a high chance of statistical false positives.
- Most importantly, there was no control group. As a result, we have no idea whether the changes were caused by the treatment or by normal growth. The study team pointed this out and suggested that enrolling an untreated control group and subjecting the patients to multiple CBCT exposures would not be ethical. I agree, but we must remember the lack of control when interpreting the results.
- I am also far from convinced that taking multiple CBCT images of growing children is ethical without clear clinical reasons.
The other important factor we must consider with this paper is the tiny effect sizes. In fact, they are not clinically significant. This leads us to conclude again that the Carriere appliance does not seem to do much and is perhaps a complicated method of applying Class II force.
Finally, this study does not support the claims made by the inventor and manufacturer of the Carriere Motion appliance.
Emeritus Professor of Orthodontics, University of Manchester, UK.