Back to basics: Maxillary expansion.
In this latest “Back to Basics” post, we will continue with the orthopaedic theme that began last year when we talked about growth and growth modification and discussed the subject of maxillary expansion. There seems to be much maxillary development being done out there judging by the content of some orthodontic Facebook groups. This is possibly partly due to the continuing technical advances that we have seen in methods available to effect orthopaedic expansion of the maxilla – particularly bone-anchored devices.
We decided to look at the literature on maxillary expansion over the following few blogs. We will discuss conventional methods first. There are a LOT of systematic reviews on this subject; all hampered to varying degrees by a lack of high-quality investigations and significant heterogeneity between studies. In essence, there are too many case series, too many different appliances and too many ways of measuring expansion. And, of course, most studies only follow patients up over the relatively short term. We have tried synthesising what we think is the salient evidence (apologies for only including a few).
Maxillary transverse skeletal deficiency is a common clinical finding often associated with unilateral or bilateral posterior crossbites and crowding. It can be managed with orthopaedic expansion of the maxilla. This is readily achievable using a variety of appliances and techniques. The anatomy of the tooth-bearing and bony maxilla lends itself nicely to transverse force application. It is mechanistically relatively straightforward to accomplish separation of the intermaxillary suture using fixed expansion appliances, depending upon the child’s age.
A fundamental principle that sometimes gets lost when talking about maxillary expansion:
- Maxillary orthopaedic expansion aims to achieve skeletal development of a narrow maxilla. However, when prescribing this treatment, we should consider mandibular dental archform and buccal occlusal relationships. Significant expansion of the maxillary arch (either skeletal and/or dental) in the absence of posterior crossbites will inevitably require compensatory expansion of the mandibular dentition. This is likely to be unstable;
- Another thing to remember is that whilst there is a poor correlation between the maturational stage of the intermaxillary suture and chronological age, the suture does become increasingly interdigitated and complex with age. However, it is not thought to completely fuse until the late teenage years. Therefore, the older the patient, the more difficult it becomes to split the suture.
Rapid Maxillary Expansion
Increasing age and suture complexity in the late mixed and early permanent dentitions means that a robust and intensive high-force approach is required for effective suture separation. This is conventionally achieved using Rapid Maxillary Expansion (RME). This aims to maximise skeletal expansion by separating the suture and minimising buccal tipping of the maxillary molar dentition. Conventional RME is generally applied via the maxillary dentition using an appliance incorporating bands cemented to the first molar and first premolar teeth or via an acrylic plate cemented directly onto the maxillary dentition.
- Conventional RME can produce significant differences in post-expansion skeletal and dental dimensions over the short-term (+2.46 mm maxillary basal bone width; +3.09 mm alveolar palatal crest width; +5.69 mm intermolar width; +2.85 mm inter-molar root apex width; accompanied by +3.75 degrees dental tipping). However, at 4-8 months post-retention, around 10 per cent of this skeletal change can be expected to have relapsed in addition to some uprighting of the dentition.
- Over the longer term (2-14 years), it has been suggested that the skeletal effects of both rapid and slow conventional maxillary expansion are reasonably stable Nevertheless, more skeletal maxillary width seems lost when expansion is carried out in post-pubertal patients.
So conventional RME will provide significant skeletal and (greater) dental expansion, but some tipping of the posterior dentition will accompany this. Both will relapse to some extent, particularly over the short term. In the next blog, we will discuss the evidence relating to bone-anchored maxillary expansion as a stand-alone procedure and, in comparison, to conventional methods.
A version of this post appeared first on Martyn Cobourne’s and Andrew DiBiase’s Evidence-Based Orthodontic Facebook Group.
Professor of Orthodontics, Kings College, London.
Have your say!
Great read. What about expansion in the mixed dentition, is it needed in the absence of a cross-bite?
“1 in 10 children have a crossbite in the deciduous dentition. However, this self corrects in 77% of the children”.
“When we see a patient with a crossbite in the deciduous dentition, it may be wise to wait for the eruption of the first permanent molars before attempting treatment”.
Surely not needed in the presence of a deciduous Xbite, even if in mixed dentition. Even a deciduous or mixed dentition crossbite with shift off of deciduous dentition could be handled by eliminating the 1st contact deciduous causation.
Per what you’d quoted here about posterior ’dental’ crossbites as often being ‘self-correcting’ is indeed supported; however, might it be feasible to suggest that a molar crossbite might very well be associated with an underlying, and non ‘self-correcting’ maxillary ‘skeletal’ transverse deficiency?
Normative values for optimal transverse skeletal development should be based upon pre-industrial crania specimens that are archived within various museums throughout the world. To my knowledge these databases are seldom accessed/consulted by most well-intending providers of orthodontic/dentofacial orthopedic Tx providers…..yet anyway.
Some of the info noted in this piece is a little out of date since some newer work on this controversial topic has not been included. For example, I am humbled to say that I made history this year by being the inventor of the first palatal expander to be FDA cleared as a device for the treatment of mild to moderate OSA in adults. (My other device, which combines maxillo-mandibular correction for OSA in adults, was also approved in 2014)..
Disclaimer: I have no commercial affiliation with any device/company.
I’m confused about FDA “clearance” and FDA “approval”. In one area above this “first palatal expander..for OSA” is identified as “cleared”, however later this new device is compared to a device “also approved in 2014”.
These are different degrees of FDA investigation. The “approval” implies some degree of FDA determination of efficacy (not to Cochrane standards) while “clearance” is a darn low bar that every device that’s marketed has to present. There are different classes of cleared product. Class I, Class II and Class III, where a Class I may be a new bandage while a Class III may be new pacemaker, however “cleared” product is simply one the FDA sees as similar to a predicate.
I am “humbled” to ask for clarification of this marketing discrepancy. And why it is even in an evidence-based blog.
“Over the longer term (2-14 years), it has been suggested that the skeletal effects of both rapid and slow conventional maxillary expansion are reasonably stable Nevertheless, more skeletal maxillary width seems lost when expansion is carried out in post-pubertal patients.”
The radiographs of RPEs, both panoral and CBCT, show prodigious bone separation. Acute sutural changes and skeletal displacement (rotation) do not necessarily translate to long term skeletal alterations.
All maxillary expansions, from archwire to the current TAD(MARPE), assume dentally borne retention long term.
Alveolar bone and palatal perturbations can relapse and migrate past this dentally retained skeletal expansion. I’ve yet to see 5yr and 10yr studies let alone a trial that substantiates or quantifies skeletal differences in purported skeletally expanded populations.
The TONGUE is NATURE’S palatal expander in all animals!
As long as the tongue is applied to the entire palate, back to front, from birth, it will make the space that it needs. In addition, USING BOTH HANDS TO CONTROL ROUND, natural FOODS WHILE CHEWING, enables any animal to bite into food and pull at the food, which exerts an outward force upon both arches. Only humans abandon the hands for forks, removing this aspect of growth, and live with indoor air pollution and congested noses in some places, causing the tongue to drop from the palate. ALL DENTISTS SHOULD TEACH PARENTS AND CHILDREN ABOUT THESE NATURAL WAYS TO GROW A WIDE, FORWARD PALATE.
Since the majority of malocclusions are retrognathic in the maxilla as well as the mandible, it lacks logic to omit the sagittal dimension. I await with interest the outcome of the research analysis of Dr Simon Wong’s 145 consecutive cases.
As far as I know this is the analysis of the cases and the analysis was directed at evaluating change in the Sagittal dimension.
I believe it is about the whether the cases have a good outcome in all dimensions and the follow up will monitor the longterm stability. Patients are not one dimensional