Does AcceleDent increase the speed of Invisalign?
We would all like to make teeth move faster. This new trial looks at the effect of AcceleDent on the rate of Invisalign treatment.
Recent research has shown that there is no evidence that AcceleDent increases the rate of tooth movement when evaluated in good randomised trials. However, one criticism of these studies is that the investigators have not adapted adjustment intervals to reflect the speedier tooth movement. These investigators did this in this new trial. I thought that it was interesting, but we need to look at it very carefully.
Luca Lombardo et al
EJO Advanced access: doi:10.1093/ejo/cjy076
A team from the beautiful city of Ferrara, Italy did this trial. The EJO published it.
What did they ask?
They attempted to ask this question
“Was there any effect on the accuracy of tooth movement with Invisalign when low frequency vibrations are used with Aligners replaced every 14 and 7 days”.
What did they do?
They did a 3 arm parallel group RCT. The PICO was
Participants: 45 orthodontic patients with a mean age of 27 years (range 14.8-46.9 years).
Intervention: The study had three interventions
- A: Patients had conventional treatment with aligners replaced every 14 days.
- B: Aligners replaced every 14 days with 20 minutes of vibration therapy.
- C: Aligners replaced every 7 days with 20 minutes of vibration therapy.
Outcome: Accuracy of tooth movement with respect to the prescription.
They collected data from pre and post-treatment digital models and the ideal final model. They analysed the tooth movement by superimposition on a Cartesian grid that they constructed from other tooth points. In effect, they superimposed the models on teeth that could be moving. I will come back to this later.
From this data, they calculated the accuracy of tooth movement.
They looked at individual tooth movement with simple univariate statistical analysis. They provided no information on the total duration of treatment for the intervention groups. I could not understand why they did not include this in the paper.
What did they find?
All the patients completed the trial. When they looked at the compliance data with the AcceleDent device, they found that they achieved 80% compliance for the required 20 minutes per day.
They provided a large amount of data on the amount of predicted and actual tooth movement data. I found this really confusing. As a result, I decided to concentrate on the primary outcome measure of the accuracy of tooth movement. However, this was also rather complex and was confined to degrees of rotation of teeth. In other tables, they divided the tooth movement into maxillary and mandibular teeth and again reported the movement by tooth group. They did not include information on total tooth movement in these tables. The only important thing that I got from these tables was that the differences in accuracy were small, i.e. less than 0.7 degrees.
They then highlighted the statistically significant variables with no consideration of their level of clinical significance.
Finally, they concluded that
- Vibration had no effect on the accuracy of tooth movement when aligners were replaced every 14 days.
- When they changed aligners every 7 days with vibration, there was no difference with the 14-day protocols.
But then they also stated that
“In our sample, adding low-frequency vibration to the aligner protocol enabled us to reduce treatment time by 50 per cent without compromising accuracy. This seems to align with the research, that pulsating forces are clinically shown to stimulate the cellular activity in orthodontic treatment”.
The only evidence that I could find on this was that the 7-day protocol plus vibration resulted in the same tooth movement as the 14-day protocols. Unfortunately, this is an entirely misleading and incorrect statement. They can only have reached this conclusion if they had included a group who changed the aligners every 7 days without vibration. This is because the 7-day aligner change may have speeded up tooth movement without vibration.
What did I think?
I have looked at this trial closely. I thought that there were several significant problems.
- When I looked at the overall risk of bias. They provided no information on randomisation and concealment of allocation. This puts the study at high risk of bias.
- I thought that the sample size calculation was inadequate. This was because they did not give sufficient detail on the effect size that they were hoping to detect.
- The statistical analysis was too simple. It should have been a multivariate analysis that would take into account co-founders, such as gender and start malocclusion.
- They measured the tooth movement from a reference plane that was based on the teeth. These could have moved. As a result, it was completely misleading.
- The study needed a 7-day protocol without vibration to answer the study question.
- The measurements that they highlighted were not actually of any clinical significance.
- They did not report the total treatment duration. This was a major problem because this is the most useful and clinically meaningful outcome.
I am sorry to be so critical but a refereed journal published this paper and it does make claims that may be used in advertising material. I am still confused about how they reached their positive conclusion about the effect of AcceleDent.
Conflict of interest: This project was supported by a research grant from OrthoAccel Technologies.
Emeritus Professor of Orthodontics, University of Manchester, UK.