A couple of weeks ago I published a very popular post on myofunctional appliances. This post is about a new trial that looks at their cost-effectiveness.
A myofunctional appliance is an intra oral appliance similar to a positioner. Its main advantage over other appliances is that it is preformed. As a result, we can fit it without taking impressions and getting the appliance made by a technician. In theory, this is great. I have based this post on a second paper from a trial that I have previously discussed. Emina Čirgić and a great research team from Gothenburg, Sweden did this study. The European Journal of Orthodontics published the paper.
Emina Čirgić et al
European Journal of Orthodontics, 2017, 1–7 doi:10.1093/ejo/cjx077
The team asked this question;
“Was there a difference in the costs of reducing large overjets with a preformed myofunctional appliance or an Andreasen Activator”?
What did they do?
They did a large multi-centre RCT in a general dental practice setting. The PICO was:
Participants: 97 children with a mean age of 10.3 years (SD+1.64) with an overjet of greater than 6mm.
Intervention: Myofunctional appliances
Comparison: Andresen Activator
Outcomes: Success of treatment and societal costs of treatment. This included the Direct costs (chair time) and Indirect costs (Parent time and costs).
Randomisation, concealment and allocation was clear. They collected and analysed the data blind.
General dental practitioners provided the treatment under the direction of an orthodontist. This is standard delivery of care in Sweden.
They asked the participants to wear their appliance nightly and for 2 hours during the day. This was for a total of 12-14 hours.
What did they find?
They classified successful treatment as a final overjet of less than 3mm. If the overjet was not reduced at all, they classified the treatment as unsuccessful. The mean treatment duration for the Andresen was 1.5 years and for the myofunctional appliance it was 1.2 years. This was not statistically significant.
They achieved a successful treatment outcome for only 37% of the participants.
I have extracted the process data into this table.
|Number of visits||11.45 (10.4-12.6)||8.4 (7.7-9.2)||3 (1.5–4.5)||<0.001|
|Emergency visits||0.7 (0.4–1.0)||0.1 (0.03–0.2)||0.6 (0.3–0.9)||0.6 (0.3–0.9)|
|Chair time (mins)||245 (213–277)||167 (149–185)||167 (149–185)||<0.001|
|Costs (Euros)||1548 (1366–1730)||974 (876–1071)||574 (385–764)||<0.001|
Their overall conclusions were
- Myofunctional treatment is more cost-effective than activator treatment. This was because there were no technicians costs and there was a high number of emergency visits for the activator patients.
- Both appliances had a low overall success rate.
What did I think?
I thought that this was a really ambitious study that they did in a “real world” setting. This was not easy. Importantly, this study provided data on the costs and process of treatment. These are very useful outcomes for both ourselves and our patients. Again, it was great to read a “functional appliance” paper that did not have any cephalometrics.
I am being very critical, but I spotted that they allocated more patients allocated to the myofunctional appliance than the activator. This suggests that there may have been a problem with the randomisation. As a result, this study may have some bias.
I would really have liked to see the Twin Block studied in this way and maybe this is another study.
I cannot help feeling disappointed at the low success rate for both of the interventions. When we have done studies with the Twin Block the overall failure rate was about 20%. However, specialists did these treatments and they may be more likely to be successful with the treatment than general dental practitioners. However, this is just conjecture.
One criticism that I know will come from the myofunctional physicians/orthodontists is that the practitioners did not prescribe any of the breathing exercises that they recommend. I hope that another study can be done that includes the exercises.
Finally, this is a great example of a study that can be done on myofunctional appliances. Perhaps the myobrace “scientific advisor” or the company could start working on similar studies. This just needs time, effort and a willingness to randomise.
I think that I would use myofunctional appliances, if other trials showed a higher success rate. In the meantime, I will continue to use the Twin Block because of the evidence from trials on its effectiveness.