A new study shows Invisalign Mandibular Advancement is not effective.
I’ve noticed that there has been an increase in the number of papers published on clear aligners recently. Align has been promoting the use of Invisalign for teenagers and has also developed a new appliance called the Mandibular Advancement appliance. This serves as an alternative to other functional appliances. A team has published a new paper on the effectiveness of Invisalign Mandibular Advancement. Their findings suggest that this method may be ineffective in reducing overjets.
I have discussed this appliance before, as previous research has produced conflicting results regarding its effectiveness. Nevertheless, the company and its paid clinical salesmen are still promoting it. In an earlier post on the mandibular advancement appliance, I wondered when we would see further research on this appliance. A team from Adelaide, Australia, recently conducted such research, and the AJO-DDO has published their paper.
Maurice J. Meade and Tony Weir.
AJO-DDO: Online advanced access. https://doi.org/10.1016/j.ajodo.2023.11.008
What did they ask?
They did this interesting study to ask.
“Did the use of the MAA achieve the predicted changes in overjet and molar relationship”?
What did they do?
They carried out a retrospective analysis of collected case records. The study had the following steps.
They accessed the Australian Aligner Research Database. This database contains information on Invisalign treatments that 16 experienced orthodontists did. This included records of 16,500 patients.
The team used the following inclusion criteria to select the patients for this study.
- They had an initial phase of Mandibular Advancement treatment
- Complete STL digital records at the start of treatment and the end of phase I treatment to correct the Class II malocclusion.
- The patients were compliant.
- They also needed an initial set of aligners to complete the treatment
They collected standard demographic data of the patients.
Finally, they recorded the planned and achieved overjet and molar relationship from the ClinChecks. This enabled them to collect data on the deviation from the achieved and planned tooth movement. This was the primary outcome of the study.
What did they find?
The team identified 195 patient records after excluding 103 without final records. The mean age of the patients was 12.62 years old, and 53% were female. The orthodontists used a mean of 40.2 aligners.
When they looked at the tooth movement, they found.
- The treatment reduced the initial overjet from a mean of 6.49mm to 4.61mm. This was 42% of the planned outcome.
- 47% of the patients had an overjet greater than 4mm at the end of this phase of treatment.
- The anteroposterior molar correction was 31% of what they planned.
This is not much to write home about…
Their conclusion was;
“Less than half of the planned overjet reduction and less than a third of the planned AP FPM correction were achieved with the MAA. Almost 20% of patients completed the MAA phase of treatment with an increased overjet despite a planned reduction”.
What did I think?
This large and ambitious study was a step forward for aligner research. As a result, it is important. The study findings and conclusions are somewhat controversial, and I have some concerns about the study. It is also good to see that the research team has highlighted these concerns. These are
- There is selection bias in this retrospective study due to the exclusion of 103 (34%) eligible records. However, it is important to note that the direction of this bias is unknown, which results in a significant degree of uncertainty.
- The study reports on the results at the end of the first phase of treatment, which is consistent with other studies on functional appliance treatments. Nonetheless, it is worth keeping in mind that these results are only interim outcomes since additional treatment may still be required to reduce the overjet.
- Moreover, I am uncertain whether we can consider the deviation from the planned ClinCheck outcomes as an outcome measure. There seems to be increasing agreement that the ClinCheck represents a force system and should not be employed in this manner. Specifically, the ClinCheck involves a component of over-treatment, similar to increased COS to reduce an overbite.
I have thought about these issues, and when we consider that the primary goal of phase I is to decrease the overjet, it’s safe to conclude that MAA treatment failed to achieve this objective. This finding is also consistent with another study that looked at the effectiveness of the MAA.
I am not completely convinced about using ClinCheck deviations as a reliable outcome measure, because there is a risk of misinterpreting the data. I would prefer if researchers used a well-established outcome, such as PAR or the ABO index. However, we cannot ignore the fact that this study demonstrated unsatisfactory reduction of overjet in many patients. We need to discuss the pros and cons of using ClinCheck deviations as an outcome measure.
I would like to conclude with my regular comment regarding clear aligners. It would be highly beneficial if someone could carry out a trial using a final treatment outcome measure such as the PAR or ABO index. This trial is not difficult to do, and it would help us to determine the truth about the effectiveness of clear aligners. Unless we are not interested in discovering the truth? I’m still looking for pigs on the wing.
This paper represents the highest level of evidence on the use of MA in phase I of Class II treatment that has been published. It suggests that it is not very good. I would stick with the Twin Block for Class II treatment.
Emeritus Professor of Orthodontics, University of Manchester, UK.