January 24, 2022

A massive Cochrane Review on treatment for crossbite.

There has been a large amount of interest and research into maxillary expansion. A multinational team has now condensed this into a Cochrane Systematic Review. I thought that the results were clinically relevant and fascinating.

Maxillary expansion is currently attracting significant interest from both the clinical and research point of view. Furthermore, orthodontists are making many claims about the risks and benefits of this treatment. As a result, this review is timely.

It is challenging to do a Cochrane review, and the authors provide a high level of research evidence. This review adds to our knowledge of crossbite correction.

A multinational team from Genoa, Italy, Rio, Brazil and Liverpool, UK did the review. The Cochrane Collaboration published it.

Orthodontic treatment for posterior crossbites

Alessandro Ugolini  , Paola Agostino, Armando Silvestrini-Biavati, Jayne E Harrison , Klaus BSL Batista

Cochrane Database of Systematic Reviews 2021, Issue 12. Art. No.: CD000979.

DOI: 10.1002/14651858.CD000979.pub3.

What did they ask?

As with most orthodontic Cochrane Reviews, they asked a simple question;

“What are the effects of different interventions to correct posterior crossbites”?

What did they do?

The team did a very detailed systematic review of the literature. You have to carry it out to a very high standard when you do a Cochrane review. In effect, this means closely following Cochrane methodology and editorial review. As a result, Cochrane reviews tend to be of a high standard.

In this review, the PICO was

Participants: Children and adults with posterior crossbites

Interventions: Any orthodontic (not surgical) treatment used to correct posterior crossbites.

Comparison: Different types of treatment or no treatment.

Outcome:  The primary outcome was the correction of the crossbite measured as a dichotomous outcome.

There were multiple secondary outcomes, for example, the amount of expansion, stability, TMD, quality of life, length, and cost of treatment.

They confined the review to randomised trials.

They did the study in several classical stages. The first was an electronic search of databases, followed by relevant hand-searching. Next, two authors screened the study abstracts, identified the final sample of papers, and extracted the appropriate data. Then they assessed bias with the Cochrane Risk of Bias tool. Finally, they did the relevant meta-analysis.

What did they find?

The team identified 31 trials. This is a large number for an orthodontic review. As a result, the authors had to present a large amount of data. I do not have the space to go into all their findings here. Nevertheless, I shall concentrate on their significant results.

The age of the patients ranged from 5-17 years old. Of these 12 studies included children aged 5-11 years old, 13 studied adolescents between 11-16 years old. The trials reported the effects of simple expansion plates, quad helix appliances, Hyrax, Tooth tissue borne expanders (Haas), Tooth-bone borne and bone borne appliances.

Eight reported the primary outcome of correction of crossbite. All the others reported that the crossbite correction was 100% successful.

When they looked at the risk of bias, they found 15 studies were at high risk of bias, 8 were low risk, and eight were unclear.

The investigators carried out eight meta-analyses. This is an open-access paper, so you can read all these when you can. I am just going to report in general terms.

Treatment vs untreated control

Removable expansion plates versus untreated control were effective. The odds ratio of correction using a removable plate was 26.2 (high strength of evidence). Furthermore, when they looked at the molar movement, the effect size was 3.3mm (moderate strength of evidence).

They found similar results for the quad helix when compared to no treatment. The odds ratio of correction was 50.59 (High certainty of evidence).

Quad helix vs removable expansion plate

The quad-helix was more effective than the expansion plate in correcting expansion with an odds ratio of 1.29 (Moderate certainty). There was a difference in the final intermolar distance with the quad helix of 1.48mm (Moderate certainty). Treatment with the quad helix was a mean of 3.15 months shorter than with the expansion plate.

Other comparisons

When they looked at the Haas v Hyrax, there were no differences in success or amount of tooth movement.

Similarly, there was no difference between Hyrax and fixed bone-borne appliances and Hyrax vs bone-borne appliances.

The overall implications for practice from this review were:

“For children in the early mixed dentition stage (7-11 years old) using removable appliances and quad helix appliances was an effective form of treatment. The quad helix was more effective than the removable expansion plate”.


“For children and adolescents (aged 7-16 years) there may be no difference between the Haas and Hyrax”.


“For all other appliances (bone-borne and tooth-bone borne) the evidence was of low quality and insufficient to draw any conclusions”.


What did I think?

This was an extensive systematic review. The team did this using standard systematic review methodology and did the study to a high standard. The Cochrane editorial team would have had considerable input into the review. As a result, this is an excellent condensation of evidence on the correction of crossbites.

The conclusions are clinically relevant and helpful. While they reflect our clinical experience, it is good to see that trials reinforce this. Consequently, this review gives us evidence to plan treatment and inform our patients of the risks and benefits as part of consent.

This review did not wholly update us on all the clinical controversies. This was because the authors could not find any trials that looked at MSE/MARPE. Importantly, this leads me to conclude that we currently do not have strong evidence to recommend these techniques to our patients. Unless we fall back on clinical experience. There is nothing wrong with this approach. However, we need to be honest about this and do not suggest this treatment will do more than correct the crossbite.

The jury is still out on the effects of expansion on skeletal change, breathing, etc. There is an urgent need for trials into this question. These are not difficult to do. Surely, there are some researchers out there who are interested in answering this vital question.


I have previously worked on research projects with Jayne Harrison and Klaus Batista.

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Have your say!

  1. An excellent article. Cochrane Reviews were coming in as I was retiring. However, the findings are encouraging to me as it confirms that I was using the correct technique to achieve maxillary expansion (when necessary!) using expansion plates and Quad Helix appliances over 25 years of Orthodontic practice!

  2. The results were interesting and comprehensive. However, the limitation would seem to be that the measured outcome was correction of the dental crossbite, and not true orthopedic bony expansion of the palate.

    Within that limit, it would seem possible to correct the a posterior crossbite through exclusively dental means, cause dehiscence or fenestration of the posterior roots, and still consider the outcome a success. However, if we were to clinically correct a posterior crossbite, yet cause the roots to leave the bone, I expect that most orthodontists would consider that treatment to have been a failure.

    Since reading the research of Arnie Bjork in residency, I have held to the belief that fixed expanders achieve some bony expansion, while removable appliances exclusively tip teeth to the buccal. I personally do believe that Bjork’s research has an advantage that will always make it seminal. That is, researchers will likely never again be permitted to place metal implants in human patients and measure the results with radiographs, for the sole purpose of research. Even if we are able to determine true bony expansion with today’s CBCT technology, there is no benefit to the patient post expansion. Therefore, I do believe that research showing what exactly does happed orthopedically with various expansion techniques, will never be done again.

    My clinical philosophy will have to remain the same. If I want to tip teeth buccally, orthodontic wires, CAT, or removable appliances are fine. If I want true bony expansion of the palate, I do think that fixed is necessary.

    • “If I want true bony expansion of the palate……”

      God I hope I’m not displacing the hemi-maxilla, and the corresponding bilateral maxillary-zygomatic suture, the maxillo-frontal suture, the orbital process of the palatine bone, etc. Don’t want anyone measuring orbital volume changes and interoccular increase from my “true bony expansion of the palate”.

      Me, I’m just hoping to tip the alveolar process and have it stable long term!

      An all bone supported appliance tips the alveolar process without tipping the teeth within that alveolar process. (For maximum mechanical advantage and minimum force to tip the alveolus one would have the all bone supported force as close to the alveolar crest as possible.)
      An all tooth supported appliance tips the teeth within the alveolus and tips the alveolar process, the apportioned amount I have no idea, probably patient dependent.
      The MSE appliance, with those palatal TADs and then recruiting the teeth, confuses the entire force system so that one has an undefined force system.

      Does it really matter? After one transitions to all dental appliances to retain/maintain the maxillary perturbations, those skeletal structures probably rebound to what would have been accomplished with sole labial conventional appliance dental expansion with the same long term risks to dehiscence etc. ………………..maybe.

  3. Are only trans-palatal fixed or removable (verses labially affixed conventional appliances) capable of transverse dental normalization?
    And if labially affixed conventional appliances (in the permanent dentition or approaching permanent dentition) are capable of transverse normalization why are they not included in this mix?

    Are these trans-palatal appliances, which I assume are a separate unique step, and unique price, in the crossbite “correction” process, superior to a conventional labial transverse normalization in late mixed-dentition/pemanent-dentition in cost and clinical outcome
    1. At the conclusion of active, permanent dentition, treatment
    2. Yrs after the conclusion of active treatment

    (Perhaps this is addressed in the Full Cochrane Review, but dang I can’t figure out how to get to this open access paper without an up-charge which reveals my naivete in navigating Cochrane)


  4. Thank you Kevin for drawing our attention to this excellent study. The results do reflect and reinforce our clinical experience, as you stated.

    It would be beneficial to have a better understanding of when and why a crossbite should be corrected. It is often stated by proponents of expansion for most patients, (sometimes in the absence of a crossbite), that an uncorrected crossbite will cause facial asymmetry.

    Most posterior crossbites in the mixed dentition have an associated slide, generally on the primary canines. This slide, if monitored for years, does not disappear with “asymmetric growth” during this period of rapid growth. If we are unable to get any significant condylar change with an introduced anterior slide, by using a twin block, why would we expect it with a small lateral slide? If the slide is the concern then why not treat that with judicious grinding.

    If there is an absence of a slide, why correct the crossbite in the mixed dentition, unless the goal is to introduce a slide? If there really is asymmetric growth and this is the cause of the crossbite, what will expansion do to assist in correcting this unfavourable growth?

    Crossbite correction appears to be more effective and stable if treated in the permanent dentition and some crossbites self-correct when the primary canines exfoliate.

    Why then treat in the mixed dentition? We should perhaps reassess the “problem” in the permanent dentition and correct some with archwires or cross elastics, if treatment is going to be provided anyway.

    TMJ problems are another stated reason for early correction of crossbites. Evidence?

    It appears that the decision to treat early, and often, is dictated more by the desire for wallet expansion than evidence.

    • Dear Dr. Attric

      I appreciate your call for ‘Evidence?’ relative to the statement regarding the implication that early correction of crossbites might prevent TMJ problems; I also feel this implied hypothesis should either be supported, refuted or ignored for the time being. Similar to your own concern, I also have a desire to know if there is support for your statement that. ‘Crossbite correction appears to be more effective and stable if treated in the permanent dentition…..’; and, I’d be especially grateful if you could cite a reference or two about the rest of your statement regarding crossbite self-correction, ‘…. and some crossbites self-correct when the primary canines exfoliate.’

      Thanks for considering

      Kevin Boyd

  5. Regarding expansion timing, increased risk of TMD and asymmetry – see conclusions from Thilander, 1984 Ann Arbor Symposium , “Developmental Aspects of TM Joint Disorder”. Also, The Angle Orthodontist: Vol. 73, No. 2, pp. 109–115. 2003, Egermark “A 20-Year Follow-up of Signs and Symptoms of Temporomandibular Disorders and Malocclusions in Subjects With and Without Orthodontic Treatment in Childhood”. From the article, “This 20-year follow-up supports the opinion that no single occlusal factor is of major importance for the development of TMD, but a lateral forced bite between retruded contact position (RCP) and intercuspal position (ICP), as well as unilateral crossbite, may be a potential risk factor in this respect. “

  6. Thank you Kevin for posting this Cochrane Review. Given that maxillary transverse deficiency (MTD) within the early mixed dentition (without an associated posterior cross-bite btw), in the absence of appropriate intervention will indeed reliably persist beyond, will also usually become more severe, and might become/already is, co-morbid with sub-optimal development of the mandible in the sagittal and/or transverse dimensions. Several recent and historic papers have been published regarding the QOL and systemic health benefits of RPE; if it will work in the early mixed dentition as is evidenced by the excellent Cochrane report, why would it not also work at an earlier age?

  7. Its an interesting review. I feel Early maxillary expansion needs evaluation of habits relevant to maxillary narrowing. Adult maxillary expansion needs to identify whether its dental or skeletal and select a tooth-borne or bone-borne expansion. I am not sure whether the habits were considered in this review. Habit correction is vital for the stability of the corrected crossbite.

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