A new clinical study on Invisalign Mandibular Advancement.
Several years ago, Invisalign released its Invisalign Mandibular Advancement to treat Class II malocclusion. At that point, I wrote that there was little evidence to support the use of this appliance. However, it is great that some Invisalign clinicians have now produced an interim report on this treatment.
The Mandibular Advancement appliances incorporate precision wings into the upper and lower aligners. These are then advanced to achieve progressive mandibular advancement. This is, of course, similar to other functional appliances. This treatment method may have a scope as an invisible functional appliance.
A USA and Canada-based team did this study. The Journal of Clinical Orthodontics published the paper.
Barry j. Glaser, Sandra Khong Tai, Regina Blevins, Sam Daher,
What did they ask?
They did this study to;
“Test the safety and effectiveness of this appliance in growing patients with Class II malocclusion”.
The study team pointed out that this was an interim report.
What did they do?
They did a prospective multi-centre clinical study. The PICO was
60 orthodontic patients aged 11-19 with a fully erupted dentition. They had a bilateral Class II malocclusion of at least 3mm measured at the first permanent molars.
Invisalign mandibular advancement appliances
Dental and cephalometric measurements. The secondary outcome was the quality of life.
They collected data at the start of treatment (T1), end of mandibular advancement (T2), and end of treatment (T3).
What did they find?
They enrolled 60 participants in the study. 47 of them completed the mandibular advancement stage of treatment (T2). In addition, 25 completed all treatments at T3. 55% of the enrolled patients were female. The mean age was 12.75 at the start of treatment.
Class II elastics were not used in the mandibular advancement phase of treatment but in the final stages of therapy to T3.
These were the main findings:
- The mean time to the end of the mandibular advancement phase of treatment was 12.6 months.
- The total treatment time from T1 to T3 was 25.6 months.
- These tables include cephalometric data on what I felt were the critical variables. I calculated the 95% confidence intervals, and these are in brackets.
T1 to T2 (n=47)
|ANB (degrees)||5.46 (4.86 to 6.06)||4.32 (3.67 to 4.97)||1.1 (0.21 to 1.99)||0.0152|
|CoGn (mm)||104.0 (102 to 106)||107.0 (105 to 109)||-3.0 (-5.9 to -0.0)||0.0152
|Overjet (mm)||6.2 (3.47 to 4.73)||4.1 (2.8 to 3.6||2.0 (1.18 to 2.8)||0.0001
T1 to T3 (n=25)
|ANB (degrees)||5.11 (4.29 to 5.93)||3.44 (2.5 to 4.38)||1.6 (0.07 to 3.3)||0.0412|
|CoGn (mm)||103.2 (100 to 106)||106.8 (104 to 110)||-3.6 (-7.7 to 0.5)||0.0892
|Overjet (mm)||6.1 (5.32 to 6.88)||2.7 (2.41 to 2.99)||3.4 (2.5 to 4.2)||0.0001
“Invisalign MA seems to produce similar treatment results to other functional appliances”.
They also stated that mandibular incisor angulation is well controlled, and patients rate their discomfort as low.
What did I think?
First, it is good to see that the team has produced some data on this appliance, and they should be congratulated. Nevertheless, we must remember it is an interim report. As a result, we need to be very cautious in our interpretation. The authors have been clear on the nature of the information. However, I cannot help feeling they could have been more careful interpreting the data.
This is because we need to consider the following problems with this study.
- There is no comparison with any other treatment or untreated control. This is important because we do not know the contribution of natural growth to the changes that they report.
- The differences between the means are relatively low. For example, I would have thought that most functional appliances would have reduced overjet by more than 2.0mm in 12 months.
- The confidence intervals are relatively wide. This reflects uncertainty in the data and is a result of the low sample sizes.
- They did not report any information on 13 patients who were initially enrolled. This may have altered the data.
I am not sure when this study started, but the sample size appears low? I am also a little confused about the source of the data. When I first discussed Invisalign MA in my blog, Invisalign responded to my post. In this response, they provided data on 40 participants in their study in 2019. However, they also stated that 17,000 patients had used Invisalign MA. So I am struggling to understand why they only have data on 7 additional patients between 2019 and now?
Finally, and most importantly. All the authors have a financial interest in Invisalign treatment. Unfortunately, they did not declare this in the paper. This is a major conflict of interest.
Ultimately, I still feel that we need better information on this appliance before we use it on our patients. I am unsure how long we will have to wait for a final study on this intervention to be published in a scientific journal?
Emeritus Professor of Orthodontics, University of Manchester, UK.