A new study shows how aligners close anterior open bite.
Several reports of successful treatment of anterior open bite with aligners have recently been published. This new paper sheds some light on how this is achieved.
We all know that treating anterior open bites (AOBs) can be quite challenging. Even when treatment successfully corrects AOBs, there is a high chance of relapse. Traditionally, our treatment involves intruding molars and avoiding extrusion of the incisors to prevent instability. Alternatively, we can do Orthognathic surgery, but this comes with risk. Recently, a new study has suggested that using aligners with posterior intrusion may be an effective treatment method for AOBs. The study aimed to assess the effectiveness of this approach.
A team from Seattle and Vancouver did this study. The AJO-DDO published the paper.
Does planned molar intrusion with aligners assist with closure of anterior open bite?
Sara Finkleman, Bobby Cohanim, Sandra Khong Tai, Roozbeh Khosravi, and Greg Huang
AJO-DDO advance access. DOI https://doi.org/10.1016/j.ajodo.2024.04.016
None of the authors declared a conflict. Align Technology funded the study.
What did they ask?
They did this study to
“Evaluate whether prescribed molar intrusion with or without virtual bite blocks resulted in molar intrusion and assist with AOB correction”.
What did they do?
They did a retrospective cephalometric evaluation of treatment.
The study team attempted to collect the records of consecutively treated patients. They used the following inclusion criteria. The patients needed to be older than 18, have an anterior open bite,have more than one incisor that did not have a vertical overlap and treated with aligners.
The team divided the patients into two groups.
- Patients without prescribed molar intrusion who did not exhibit a virtual bite jump were allocated to the no PMI group.
- Those prescribed molar intrusion with a virtual bite jump were placed in the PMI group.
They evaluated cephalograms at the start and end of treatment. One blinded operator traced the cephs.
Finally, they used ClinCheck software plans to identify the amount of planned tooth movement.
They calculated the sample size before the study, and analysed the data with the relevant uni and multivariate statistics.
What did they find?
6 orthodontic offices took part in the study. The number of patients treated in each office ranged from 2 to 9. The total number of patients in the study was 36. Of these, 15 were in the no PMI group and 21 were treated with PMI.
They provided a lot of data through diagrams, scatter plots, and cephalometric tables. My ageing brain was not able to process all this information. Nevertheless, the authors included the most important information in the text and abstract. This revealed that the average overbite change was 2.5mm for the no-PMI group and 3.2mm for the PMI group.
The treatment left the vertical molar position in the no-PMI group relatively unchanged. Whereas all molars in the PMI group had small amounts of mean molar intrusion from 0.2-0.7mm.
The average molar intrusion for the PMI group was 0.7mm greater than the no-PMI group.
They concluded
“Most of the AOB correction was incisor extrusion and retroclination, whether or not the clinician planned molar intrusion”.
What did I think?
I usually don’t review retrospective cephalometric studies because of the high risk of selection bias in the study design and the complexity of multiple cephalometrics. Nonetheless, it’s important to acknowledge that research on aligners is relatively new and this study starts to fill gaps in our understanding of aligners. However, we do need to remember that is likely that this study has a great deal of selection bias. Importantly, the authors acknowledge this in their discussion.
I have carefully considered their findings. Aligners are an effective method for treating AOB, and the correction may also be relatively stable. When we consider the effects of treatment, aligners seem similar to fixed appliances with TAD support. Nevertheless, I am still concerned that most of the tooth movement is due to the extrusion of the upper incisors. Clinical experience and hearsay suggest that this is very unstable. However, it’s important to note that this impression is based on a very low level of evidence.
Final thoughts?
I was also very interested to see that Dr Maz Moshiri, a major KOL for Invisalign, discussed this paper on orthodontic social media. He presented several well-documented, fully treated case reports with tracings and superimpositions. This is a stark contrast to poorly documented cases from other KOLs. It’s evident to me that aligners could be an effective method for treating anterior open bites (AOBs). We now need prospective studies to validate this assertion.
Based on my clinical experience treating AOB with aligners over approximately seven years, I contend that their ability to correct AOB by molar intrusion without using TADs is under appreciated. AOB is only about 2-4% of cases so my boutique practice does not treat enough for me to write a peer reviewed paper but I’m very impressed with what I have seen to the point that, unlike any other malocclusion, I would refuse to treat a patient with fixed appliances rather than aligners if they insisted on fixed.
This study has some very serious flaws when it comes to sample selection, among other things. It beggars belief that 6 offices only treated 36 AOB patients with aligners in 10 years! How can that possibly be?? Especially given that one of the authors is a KOL for Invisalign, and lectures frequently about closing AOBs with aligners. The authors did not define what “completed treatment” meant. It is very likely that open bites that did not close were considered to be “incomplete”.
Otherwise this would mean a 100% success rate for all AOBs treated with aligners, between 2011 and 2021!
This is simply impossible, given the many challenges with treating open bites, not the least of all being compliance. If one were to look at the examples the authors presented, except for #6, these are all the types of cases that we see in our offices everyday! One or more incisors that do not have vertical overlap means there should be 100s, if not 1000s of these type of cases between 6 locations. Why then did we see only 36 AOB aligner cases between 6 offices?? The authors appear to have cherry-picked the cases where the AOB was closed, and the others were simply considered incomplete. Thus, any estimates of tooth movement are likely to be overly optimistic
One of the authors appears to be an Align KOL, yet no conflicts of interest were declared. That seems to be a huge omission. Perhaps the authors can clarify?
The combination with a slight expansion together with intrusion will add to the treatment outcome since we will get a relative intrusion. In addition, sequential intrusion, tooth by tooth, starting from the distal and moving mesial is superior to en mass intrusion of molars. This is of course more time consuming but more predictable then en mass intrusion. We will publish the results from 30 consecutive cases in the near future.
Retrospective study and end of treatment CEPHs?
(sorry about the capital letters, but I’m not going to type lateral cephalom etc )
I can understand end of treatment CEPHs in a prospective study where you get approval for the CEPHs, but if you started these patients unaware that you were going to do a study, why are you taking a CEPH at the end of treatment? And 6 orthodontic practices (I’m not sure that it says the number of operators) had the same approach to radiographs.
Stephen Murray
Swords Ortho
It is disappointing to see reports like this in orthodontic journals that aspire to high academic standards. The authors explain that ‘in the retrospective arm of this study patients with AOB who had completed treatment were recruited’ (sic identified retrospectively). They go on to state that ‘All efforts were made to recruit consecutively treated patients’ yet there are no numbers of potential participants identified retrospectively, the number of those identified who fulfilled the inclusion criteria and the number invited for a follow-up examination. Without this information we are unable to judge how biased the sample is. Prospective follow-up (at least 1 year after completion of treatment) stability data are presented for only 14 out of 36 participants. If this were a report of a clinical drug trial with potentially adverse effects, I would not trust the findings. I think that editors of reputable journals and their reviewers should now routinely reject reports of studies with retrospective trial designs.
Yes. Possibly chance findings with the methodology flaws. The old removable orthodontic appliances with posterior bite planes were just as effective in good compliance patients. Talking to Ravi Nanda about tooth movements with aligners. Its all related to the amount of IPS rather than true intrusion.