Open Bite Closure: Should we extract?
Closure of open bite can present a mechanical challenge with extractions, which may assist closure by promoting mesial movement of the posterior dentition. The ‘stability’ of open bite reduction is known to be particularly problematic. I don’t think the two words sit well in the same sentence. Open bite correction is typically unstable, and to compound matters, we don’t seem to have proven ways of retaining open bite correction either.
A previous publication from this prospective cohort study involving a network of North American practices, for example, suggested that fixed retention may not mitigate the issue. But are there treatment-related factors that ensure a more predictable and ‘less unstable’ result?
This interesting study involved reanalyzing previously published data. The authors specifically assessed the potential impact of extractions on the success of active treatment and the recurrence of open bites at the 12-month follow-up.
The study was coordinated in Seattle. Ideally, I would like to visit Seattle and combine my visit with a skiing trip.
Geoffrey Greenlee, Jessica Collins, Brian Leroux et al.
Angle Orthod. 2025.
What did they do?
They conducted a follow-up of a multi-centre prospective cohort with patients recruited between October 2016 and December 2017.
Participants and Interventions:
Participants were aged 18 years or older with no vertical overlap of at least one incisor and no incisal contact on any of the incisors. They underwent active treatment with or without extractions using fixed appliances. Subjects receiving treatment involving orthognathic surgery, mini-implants, or aligners were excluded. All patients presented with crowding in at least one arch. The extraction group comprised participants who had at least one premolar, canine, or incisor removed.
The authors evaluated the stability of open bite correction over a minimum period of 12 months using cephalometry and clinical photographs. The photographic open bite severity index (POSI) has scores ranging from zero to 6. Zero represents vertical overlap involving all four incisors, while a score of six was given for open bites spanning the incisor to premolar region.
What did they find?
In total, 115 participants with a mean age of 33.2 years were included, with 33 having undergone extractions and 82 treated non-extraction. The extraction group was younger (29.6 versus 37.7 years). Unsurprisingly, extraction patients exhibited more crowding and lip protrusion at baseline. Pre-treatment open bites were notably marked with a score of 4 (indicating no overlap of all four incisors), being the most common in both groups.
Success (defined as complete open bite closure or a residual open bite involving only a lateral incisor) was achieved at debond in 93%. This increased to 97% with extractions and 91.5% without them. However, according to the inferential statistics, positive overbite was unrelated to the extraction pattern or any other variable. As anticipated, extractions led to a greater reduction in the inclination of the incisors, with an average of 4 mm retraction in the extraction group. This tendency diminished in the presence of greater crowding.
Short-term stability (up to 12 months) was examined within a smaller sample, with all 11 patients undergoing extractions (100%) and 49 (89%) in the non-extraction group maintaining open bite closure. No statistical difference was observed, although this conclusion was drawn from limited data.
What did I think?
I think that this was an interesting study. It is great to see a prospective study that considers the success of open bite therapy and indeed the associated stability, albeit in the short term.
I have reviewed a previous study based on this data and continue to feel that the use of numerous ‘real-world’, primary care settings is all too rare in orthodontics.
The results are encouraging with the success of treatment being high, although we know this to be founded on good diagnostics. The preliminary stability data is also encouraging.
As with the rest of the study, the methodology and writing are excellent. The sample size is adequate, although there was significant attrition of the post-treatment data. The number of participants in the extraction group was low, with just one-third of the participants considered at this point. The descriptive data, therefore, points to a potential benefit associated with extractions, although the statistical power was insufficient to fully interrogate this.
The authors opted to exclude those treated with mini-implants. This is appropriate in terms of rigour, limiting the potential confounding effects of any associated reduction in the vertical dimension. However, I do think that considering the relative stability of TAD-based intrusion in the present sample(s) would be interesting, as intrusion is now increasingly accessible. It may be that this is considered part of allied research.
The observation period was limited to 12 months, and details of the retention regime were not presented. The authors recognise that a longer evaluation could provide more insights.
Unfortunately, there was a considerable degree of attrition from the sample by the 12-month mark; thus, later assessments may be challenging. As always, the value of further prospective research remains, with the challenge of loss to follow-up being significant during sample size calculations.
What can we conclude?
The successful closure of open bite was nearly universal in this sample, treated both with and without extractions. Short-term follow-up revealed encouraging levels of stability; however, a larger sample would be necessary to better understand whether extraction-based treatment leads to more stable occlusal correction.
Professor of Orthodontics, Trinity College Dublin, The University of Dublin, Ireland
Let us see the long-term (3 to 5 years) results…I don´t think it will be the same
I have found that Asynchronous short Class II elastics from the mesial of the upper canines to the distal of the lower first premolars are very effective at closing anterior open bites and correcting malocclusions with minimal mandibular rotation. The elastic force vector is anterior to the maxillary center of rotation but it runs through the center of rotation in the lower arch. A large moment is only produced in the maxillary arch, closing the open bite and reducing or correcting the Class II malocclusion. Class III, open bite malocclusions can also be corrected with the same mechanics due to the lower arch being more forward. I have the records on a Class II and Class III case that I have finished and would be happy to share them with you. They are in a Power Point format.
Hi Padhraig:
It’s interesting that you describe the treatment of AOB as a mechanical challenge. This is one of the assumptions that the Spatial Matrix Hypothesis (SMH) addresses. As an orthodontist/dentist, our attention seems to focus on the teeth without thorough assessment of the contextual tissues. The SMH suggests that ‘deformity follows dysfunction’. In this case, the AOB represents a dysfunctional spatial matrix in which the tongue plays a pivotal role since AOB is often associated with tongue thrust. Even tho’ a thrust may not be apparent clinically, the position of the tongue can perpetuate AOB. Thus, the tongue becomes an arbiter of long-term stability. The question arises as to why the tongue is inappropriately positioned. To answer this, the clinician needs to assess the maxilla. Often, AOB is associated with a gummy smile and a narrow, high-arched palate. Thus, the tongue is displaced from optimal positioning and function. The etiology of the maxillary dysmorphology remains controversial also, altho’ genetic and epigenetic influences play a role. The size, shape and position of the dysmorphic maxilla in turn impacts on the mandibular spatial matrix, which exhibits developmental and/or postural compensation, resulting in AOB.
The SMH teaches that decompensation is a first step in management, altho’ in this case, re-training muscle memory (oral myofunctional therapy) may be central to clinical stability. In AOB cases, a biomimetic (not mechanical) approach could be taken to correct the maxilla thru “palatal expansion”. Palatal expansion represents a broad range of clinical protocols, which I will not discuss here. In any case, the change in midfacial shape space is primarily to accommodate the tongue and then the mandible can follow suit. Final orthodontic finishing can help with enhancing a positive overbite and posterior occlusal interdigitation.
In 2006 we presented at the European Orthodontic Society meeting, showing how we closed AOB in kids. Later, we published similar findings in adults (1). Note also that AOB is not a single condition (a bit Class III malocclusion in that respect). I consider that there are 4 sub-types of apertognathia, which I won’t describe here for the sake of brevity. Hope this note helps others in the treatment planning of AOB cases.
Reference
1. Harris WG, Singh GD. Resolution of ‘gummy smile’ and anterior open bite. J Amer Orthod. Soc. 13(4):30-34, 2013.
Good morning Sir,
Thank you for highlighting this study on AOB.
As it has been pointed out that AOB is multifactorial, would it be prudent to delay the treatment similar to Orthognathic cases where we try to intervene after skeletal growth is finished?
Would it be better that AOB becomes a routine criteron for referral to secondary care Orthodontics where Post-graduate supervision and research is more readily available?
This way the children with chief complaint of AOB (especially with minimal crowding) may be able to access NHS treatment where they qualify (even after turning 18).
Thank you.
Yours sincerely,
Mr Karun Sagar
Orthodontic Assistant