Let’s have a look at the Carriere Motion III appliance!
In previous posts, we have looked at the Carriere II appliance. You may remember that we concluded that this appliance was just another method of applying Class II forces.
There is also a Carriere Motion III appliance! This recently published paper looked at the effects of this form of treatment. Luis Carriere highlighted the article in social media posts and felt that it was “excellent”. So I thought that I should have a good look at it.
A team from Michigan did the study. The Angle Orthodontist published the paper.
McNamara J et al. Angle Orthodontist, Vol 91, No 2, 2021 DOI: 10.2319/073120-669.1
As you know, I do not usually review retrospective studies unless they are controversial, or I feel that they provide us with helpful information, albeit with a high risk of bias. This paper ticked both of these boxes.
What did they ask?
They did this study to ask the following question:
“What are the treatment effects of the Carriere Motion III appliance on relatively non growing Class III patients”?
What did they do?
They did a retrospective study of patients who had Carrier Motion III treatment as part of a comprehensive course of orthodontic treatment.
The records were selected from patients who had an initial phase of treatment with the Carriere Motion III appliance, followed by fixed appliances.
They got the records from two sources. The first was Luis Carriere’s clinic in Barcelona, and the second was McNamara Orthodontics in Michigan. The records had to include lateral cephalograms taken at the start of treatment after removing the CM3 and after fixed appliances. If the patient did not have these three serial views, they excluded them from the study.
They used the CVM technique to check that the participants had stopped growing.
Their final sample of patients included 35 from Luis Carriere and 14 from the McNamara clinic. They then excluded 11 of the patients for having incomplete records or not satisfying other criteria. This meant that they rejected 25% of the original sample.
They did not use a matched control, but they compared the treated group with the records of 125 untreated Class II subjects.
They then looked closely at 11 skeletal and seven angular measurements from the cephs, using many univariate tests across the groups and stages of treatment.
What did they find?
Most of the data that they presented were concerned with the cephalometric analysis.
- The mean age of the CM3 patients was 18.6 years (SD=6.7). The duration of the CM3 treatment was 6.3 (SD=4.3) months.
- The overall treatment time was 19.2 (SD=6.5) months.
- When they compared the CM3 sample and the Class I untreated groups, there were many differences.
The cephalometric analysis showed:
- There was minimal skeletal change.
- The upper incisors and molars moved forwards by almost 2mm.
- In the lower arch, the lower incisors moved anteriorly by 0.5 mm during phase 1 and a further 1.9mm in phase II. Similarly, the molars moved forwards by 1.8mm, but there was a rebound during phase II, resulting in a total distal movement of 1.4mm.
Their overall conclusions were;
“The Carriere Motion III appliance is an effective and efficient adjunct to fixed appliances. Most of the treatment effects were dento-alveolar. No noteworthy skeletal changes can be anticipated with the CM3 appliance”.
What did I think?
A highly respected team of investigators did this study. They used their “tried and trusted” retrospective methods and have published many papers of this type. When we look at this method, we have to consider a high risk of selection bias. Importantly, other research methods have now superseded it—for example, the prospective cohort or RCT. As a result, I did not agree with Dr Carriere’s opinion that it was excellent. However, this is the only research that we have on this appliance.
Unfortunately, this study suffered from several issues.
- Firstly, there was marked selection bias, with the authors excluding 25% of the initial patient records. Importantly, we do not know the direction of the bias. We simply need better research.
- It was also not clear why they compared the patients with a historical record of Class I subjects. This step did not add to the paper.
- The primary outcome measures were cephalometric values that they analysed with multiple simple statistical tests. This analysis increases the risk of false positives. I also felt that many of the effect sizes were not clinically significant.
I was concerned that they did not declare the apparent conflict of interest of Luis Carriere. He is a major KOL for Henry Schein Orthodontics, and the appliance has his name on it! Notably, he selected most of the patients from his clinic. Again, I will emphasise nothing wrong with a conflict as long as it is declared. I am surprised that the Journal did not include the conflict.
Finally, I am left with the feeling that the effects were similar to Class III elastics. This brings us to the suggestion that the Carriere Motion III is similar to the Carriere II. At present, we have to wonder if this is just a fancy and expensive way of applying intermaxillary elastics? Perhaps, someone will do a much-needed study comparing elastics with the Carriere appliances? Or do we just believe in the publicity?
Emeritus Professor of Orthodontics, University of Manchester, UK.