June 07, 2021

Simple removable appliance expansion is effective?

Recently, there has been an increased interest in the expansion of the maxillary dental arch.  This has involved the development of seemingly more complex methods of expansion.  But have we forgotten that simple techniques may also work?  This new paper looks at maxillary arch expansion with a simple removable appliance.  It is not perfect, but it is worth considering.

Maxillary arch expansion appears to be becoming increasingly complex with the development of RME, Hybrid RME, Maxillary Skeletal Expansion and other methods.  All these methods promise both dental and skeletal expansion. Orthodontic gurus are making claims on the use of these appliances and their effect on the airway. We have discussed these in earlier blog posts.  Sometimes, I wonder whether we forget the simple methods of orthodontic treatment. Although, I will concede that I may sound like an old Professor reminiscing about the old days and our techniques. Nevertheless, this new paper has made me think about the way that we used to correct crossbites.

A team based in Leuven, Belgium, did this study. The European Journal of Orthodontics published the paper.

Short term effects of interceptive expansion treatment: a prospective study

A.-S. Van de Velde et al.  EJO: Advanced access doi:10.1093/ejo/cjab006


What did they ask?

They did this study to determine if a simple removable expansion appliance was effective at interceptive treatment of anterior and posterior crossbites

What did they do?

They did a short-term prospective cohort study of simple removable appliance expansion.

The inclusion criteria for the patients were that they were receiving expansion treatment for crossbite, lack of space, canine impaction and functional shift.  The patients were all in the mixed dentition. They also had to have complete records of photographs, digital dental casts, panoral and cephalometric radiographs at the start and end of treatment.

Resident/postgraduate orthodontic students provided the treatment using a removable appliance expander with a midline screw, molar capping and a labial bow.

They used slow expansion, and the patients turned the midline screw at a rate of 0.25mm expansion a week.  They continued this treatment until they had corrected the transverse problems.

At the end of the expansion, they asked the patients to continue to wear their appliances for two months of full-time passive wear and two months of part-time wear.  They did the final data collection after this period.

The primary outcome measure was whether they had corrected the crossbite. The other outcomes were whether a functional shift had been corrected and the sagittal relationship of the molars.

What did they find?

The authors presented a large amount of data, and I shall concentrate on what I feel are the main findings.

They enrolled Two hundred seventy-four patients into the prospective cohort.   Unfortunately, 48 did not meet the inclusion criteria because of a lack of records, non-compliance or change to an external orthodontist, a dropout rate of 17%. I shall return to the implications of this later in my post.

The mean age of the patients at the start of treatment was 8.7 years.

At the end of treatment, 98% of the patients had their crossbite corrected. The mean increase in intermolar width was 3.8mm.

Their final conclusion was:

“A removable appliance plate was effective in improving the transverse dental dimensions of the maxilla in the mixed dentition”.

What did I think?

I thought that this was an ambitious study that required a lot of careful treatment and data collection. While it is not an RCT, its prospective nature provides a reasonably high level of evidence. As with most studies, there were some limitations. These were, firstly, they lost 17% of the original patients because of dropouts. This problem meant that the study suffered from selection bias, particularly concerning non-cooperation. If they had included the data from these patients in the analysis, I am sure that it would have changed the results.

Furthermore, there was no untreated control. As a result, we cannot discount that some of the crossbites may have self-corrected.

Nevertheless, the findings do illustrate that this simple interceptive treatment is highly effective for dental crossbites.  Furthermore, it may be that general dental practitioner can do this treatment. However, in an earlier study, the authors suggested that specialist practitioners are more effective than generalists.

We also need to remember that this is a short-term study. I am interested in seeing the long-term follow-up to this study as I am sure that the results will be fascinating and clinically relevant.

Final thoughts?

Finally, it is interesting to consider this treatment compared to much more invasive treatments, for example, MARPE. We could use a removable appliance for the straightforward dental case rather than screwing expansion devices into young children. This question would be an excellent subject for a trial.

Since publishing this post, I have received some great comments. Most of these have pointed out that when we expand we are looking for skeletal change. In this respect, my comments on MARPE are misplaced.  I have looked at these again and I wonder if was being a bit too “dry” when I commented. I certainly agree that when we want skeletal change then we should use the best skeletal expander. However, when we just have a dentoalveolar problem then we can use a simpler method.  I feel that my comment was directed at the “expand at all costs with as complicated method as possible” orthodontist.

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Have your say!

  1. previous studies have shown that removable appliance therapy is not effective for skeletal expansion

  2. Hi Kevin, thanks for your review of the paper. Your comments are making me want to actually read the paper itself, because I can’t believe you’d compare a MARPE to a Schwartz Plate or other removable expander! I don’t think anybody would ‘screw’ an expander into a young child that simply has a dental crossbite. I think it’s been well demonstrated that removable expanders can tip teeth out of cross bites, and if tooth position was the real problem, that may be an adequate solution. However frequently there is an underlying skeletal issue that a removable appliance will not be able to correct. As an orthodontic specialist I am trained to diagnose the problem correctly and I am able to tell the difference. I would not recommend the average general dentist try this, but would like to see these cases referred out for specialist assessment and treatment. The mixed dentition presents a unique window of opportunity where we can create tremendous changes for our patients’ benefit. I wouldn’t want to see it wasted with a removable expander when in fact the patient needs an RPE.

    • I fully agree, Sebastian. Many patients with transverse skeletal discrepancies do not demonstrate dental crossbites. Typically our diagnosis of the transverse dimension includes low dose CBCT to quantify the discrepancy and correction is best completed with an RPE.

    • Agree!!!

    • Well said.

    • you can certainly get stable skeletal expansions in maxillae with removable appliances
      This combined with myofunctional correction of the soft tissues corrects crossbiltes and mandible retrusion
      Jon Mews studies on twins is the indisputable
      demonstration of this.

  3. Dear Kevin did you never see my paper Mew, JRC “Relapse Following Maxillary Expansion: A Study of 25 Consecutive Cases” American Journal of Orthodontics. 1983; 83: 56-61. “The net expansion had been 3.5 millimetres and this had subsequently not relapsed” On average there was no relapse 2½ years out of all retention. Although some had relapsed others had continued to widen. Interesting don’t you think?
    Best wishes John.

  4. HI Kevin, thanks for this
    Increase in intermolar width of – let’s say – 4mm mean. 0.25mm per week expansion. 16 weeks.

    It’s not clear was there more expansion that relapsed down to 4mm, whether 4mm was obtained and was stable or whether 4mm was obtained and relapsed a bit.

    They required 16 weeks of active wear, then 8 passive then 8 part time passive. I would find that a fair commitment from my patients to get that degree of removable compliance without wearisome rows. And indeed, non compliance was cited as one reason so many kids dropped out.

    If that was a 6mm crossbite or an 8mm one then it’s very demanding on compliance – I think – and give more scope for breakages and lost appliances. Fixed RME would sort out the expansion relatively quickly and the passive phase would be much the same regardless of the amount of expansion.

    When I moved from URAs to RMEs I never really had the urge to return and this hasn’t encouraged me to change my mind.

    Stephen Murray
    Swords Orthodontics

  5. Hi Kevin:
    I have just written a chapter on this subject (RME appliances vs MSE surgery) for an ENT book that will be published later on this year. So, I believe there are many deficiencies with this current paper as well as your informative review. One of the issues with the paper is the appliance design (as well as its materials and the protocols used). In my opinion, there is nothing “simple” about the therapeutic approaches to the manipulation of the midfacial complex.
    When you say “we cannot discount that some of the crossbites may have self-corrected”, please could you provide one study from the medical, dental or orthodontic literature to illustrate this self-correction? I have never seen this putative phenomenon and wonder about a possible mechanism for self-correction. In addition, the conclusion of the study is flawed since it omits the pediatric qualifier. You might be aware that our sleep physician colleagues are investigating the possibility of Adult maxillary expansion as a possible alternative to CPAP, MSE etc. for the treatment of OSA. This approach is the subject of a book that I wrote during the pandemic, and which has now been published.

  6. Kevin,
    How they get full maxillary expansion if the appliance had a labial bow? Did they just measure molar width change?
    John McDonald
    Salem, OR

  7. Bonjour Dr OBrien,
    I would raise the same concerns of Dr Cooper and Dr Baumgaertel.
    1- Age of the sample: 8,5 y. It is very unlikely that a MARPE with 4 tads would be use for such young population. Hybrid Hyrax with 2 TAD could be use, but it would be for a different purpose, like Facemask therapy in cl III patient.
    Hence, one can not compare MARPE done in post pubertal and adult patient with prepubertal children.
    2- Dental expansion vs skeletal expansion. I would be very skeptical that they obtained any skeletal expansion. This raise the question of the alveolar housing. Does the bone follow the tooth or does the tooth move through the bone and buccal cortical plate?
    3- IMHO, the researcher ask the wrong question. The question is not if a removable expansion can achieve expansion to correct a posterior xbite.
    The question should be: How much skeletal expansion is obtained with a removable device compare to a fixed expansion device?

  8. Kevin,
    This is a flawed study with ambitious conclusions. I am surprised to read your final thoughts. Comparing RPE or MARPE to a removable expander with a labial bow is like comparing apples and oranges (dental tipping vs. skeletal expansion).
    I agree with most of the comments noted above.
    Ravi Nanda

  9. I will leave comments on the comments…It does work.
    to the comment on expansion with labial bow.. if there is a sagittal issue and you reduce the acrylic on the lingual the labial bow will reduce the overjet coincident with the expansion.
    For stability.. we have been expanding most of our patients for the past 40 years. Very early we recognized Our Native American population had an inherent problem with arch width. To correct it we utilized various Mx appliances till we finally settled on a Maxillary Transverse and depending on retention and stability requirements with and with out occlusal coverage. It took awhile but using a quarter turn per week resulted in the most stable cases–long term..25-35 years out.
    Most of our patients were still growing but we did manage to successfully treat a number of adults with the same protocol but with longer retention.

  10. This paper and others promoting dental/alveolar expansion are flawed with the basic misunderstanding of skeletal vs dent/alveolar physiology. The skeletal NASAL /maxillary component is the primary focus. A CBCT evaluation identifies if there is an obstruction within the nose and if the nasal volume itself is small. All relating to the transport of NO from the sinus’. It is imperative for nasal breathing vs mouth breathing…… performance and longevity colleagues! Sutural expansion is the Key, and a savvy ENT is necessary. Dental crowding, and narrow palates are a secondary and compensatory result of a Nasal obstruction and mouthbreathing primarily when supine. Low tongue posture=narrow arches. Nasal clearing and skeletal suture expansion is hand in hand. Dental/alveolar ‘widening’ doesn’t do it…. the patient is left with a potential progression to OSA.

  11. Since publishing this post, I have received some great comments. Most of these have pointed out that when we expand we are looking for skeletal change. In this respect, my comments on MARPE are misplaced.  I have looked at these again and I wonder if was being a bit too “dry” when I commented. I certainly agree that when we want skeletal change then we should use the best skeletal expander. However, when we just have a dentoalveolar problem then we can use a simpler method.  I feel that my comment was directed at the “expand at all costs with as complicated method as possible” orthodontist.

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