The Carriere appliance works by moving teeth!
The Carriere appliance is a Class II corrector. This is promoted heavily by Henry Schein Orthodontics and their Key Opinion Leaders. They make many claims about its effectiveness, and I have posted about this several times before. I also discussed two low-quality papers that measured the effects of the appliance. One stated that it was effective, and the other suggested that it was not effective. This new paper looked at its effect on the dentition in three dimensions using CBCT technology.
A team from St Louis, USA, did the research. The Angle Orthodontist published the paper.
Daniel Areeponga et al
Angle Orthodontist: On line. DOI: 10.2319/080919-523.1
What did they ask?
They did this research to answer this question about the Carriere appliance:
“What are the three-dimensional treatment changes of the Carriere Motion Appliance in Class II adolescent patients”?
What did they do?
They carried out a retrospective investigation of a case series. They analysed a sample of 59 adolescents (16 boys and 43 girls). The inclusion criteria were
- Unilateral or bilateral Class II molar relationship.
- Bilateral Class II canine relationship
- Bilateral use of the Carriere Motion Appliance (CMA)
- Availability of pre-treatment (T1) and post CMA use (T2) CBCT measurements. They defined T2 as successful completion of molar correction. The clinicians took these CBCT images after a mean interval of 4 months. I am not sure that many orthodontists can justify this radiation exposure?
They divided the patients into two groups depending on the skeletal classification. Group 1 comprised 27 sets of records with an average ANB of 2.9 degrees. Whereas, Group 2 was 32 patients with an average ANB of 6.06 degrees.
They collected the case records from the offices of Drs Paquette, Shipley and Schreiner. These three well know KOLs are paid by Henry Schein Orthodontics, who market the CMA. You know where this is going! But more about this later.
They did not provide any information about the numbers of participants treated by each orthodontist. They all used the standard CMA protocols.
The primary outcome measures were treatment duration and analysis of three-dimensional tooth movement.
What did they find?
The mean treatment duration of the molar correction was 4.9 months for group 1 and 4.2 months for group 2.
They presented a large amount of data on dental changes. Importantly, they measured 36 variables for each group and ran univariate statistics across all of them. This approach is bound to find many statistically significant differences. Indeed, there were differences for nearly all the variables.
As with most cephalometric style papers, most of the effect sizes were small. I do not have the space to present these here. Nevertheless, I would like to illustrate the data with the movements for the upper molars for group 2. I also calculated the 95% confidence intervals from the standard deviations that they presented.
The data showed that the upper molars moved distally by 1.67 (95% CI= 1.12-2.2)mm, tipped distally by 6.45 (4.8-8.0) degrees and rotated distally by 4.64 (2.6-6.2). These wide confidence intervals reflect the small sample size and the high level of uncertainty in this data. All these small differences combine for overall molar correction.
The authors nicely summarised the clinically important effects as:
- Distal movement and the tip of the upper canines
- Distal movement and the tip of the upper molars
- Mesial movement of the lower molars
- Flaring of the lower incisors.
In effect, the CMA acted like Class II elastics.
“The CMA corrected Class II malocclusion through distal tipping and rotational movement of maxillary canines and molars and corrected mesial tip of lower molars”.
What did I think?
I thought that this study was interesting because the authors had adopted the simple approach of evaluating a case series. While this was a low level of evidence, it does illustrate the effects of the appliance. Importantly, their conclusions reflected the study design and they did not make any other claims for the effectiveness of the appliance. This could be a good “first step” paper.
Nevertheless, we need to be careful in interpreting their findings for the following reasons. Importantly, there was not a control group. As a result, we must assume that some of the tooth movement will have occurred during natural adolescent growth and is not due to the CMA.
Furthermore, the cases had all been successfully treated. There was also no indication of how the patient records were selected. As a result, the sample could be subject to considerable selection bias. It is relevant to point out that Drs Paquette, Shipley and Schreiner received substantial payments for their work as KOLs for HSO from 2016 to 2018 according to Open Payments. While there is nothing wrong with receiving these payments. Their conflict was not declared. I will just leave this here.
This paper shows that the Carriere Motion Appliance works the same as Class II elastics. I cannot help feeling that the CMA is a heavily promoted expensive way of applying Class II mechanics?
Emeritus Professor of Orthodontics, University of Manchester, UK.