March 19, 2018

A massive Cochrane systematic review tells us a lot about Class II treatment.

We have updated our Cochrane review on Class II treatment. The results are interesting and clinically relevant.

When you sign up to do a Cochrane review you have to agree to keep it up to date. This post is about the updated review that was published this week. I will declare an interest. I am a co-author on this paper and it included data from trials that I was involved with.

Orthodontic treatment for prominent upper front teeth (Class II malocclusion) in children and adolescents.

Cochrane Database of Systematic Reviews 2018, Issue 3. Art. No.: CD003452. DOI: 10.1002/14651858.CD003452.

Batista KBSL, Thiruvenkatachari B, Harrison JE, O’Brien KD.

A team from Manchester, North of England, did this study. The lead author is Klaus Barretto-Lopes, who worked with us for a year and has returned to Brazil. He does the excellent Portuguese translation of my blog.

We tried to answer three main questions;

1               What are the effects of treatment provided in 1 or 2 phases (early v adolescent)?

2               What are the effect of later treatment with functional appliances vs untreated controls?

3               Are there any difference in the effects of the various types of functional appliance?

What did we do?

We followed standard Cochrane methodology and only included randomised trials in the review. The PICO was

Participants: Children receiving orthodontic treatment to correct prominent upper incisors

Intervention: Any type of functional appliance

Control: Delayed or no treatment or other functional appliance

Outcome: Primary outcome was overjet. Secondary was skeletal relationship, harms, self esteem.

We carried out standard electronic and relevant hand searches. We evaluated the trials for bias using the Cochrane Risk of Bias tool.

What did we find?

After applying all the usual filters, we selected a final sample of 27 trials that provided data on 1251 participants. These were broadly divided into;

  • Four trials looking at early treatment for children aged 7-11 years old.
  • Twenty evaluating treatment of children aged 10-15 years old
  • The remaining seven treated children between 9-13 years old.

We divided the studies into two main groups;

  • Those that looked at early treatment (2 phase) and followed the participants until all treatment was completed when they were older.
  • Studies of later (adolescent) treatment. (1 phase).

We found that most of the studies were rated as high or unclear risk of bias. This was mostly for issues with blinding, concealment and randomisation. The other main reason was for attrition bias because of “drop outs”. I shall return to this later.

These are our main findings;

Early treatment

When treatment was provided early the only effect of treatment was a 12% reduction in the incidence of incisal trauma. At the end of all treatment 19% of the early treatment group had experienced trauma. Whereas, 31% of those that did not have early treatment had trauma.

There were no effects of early treatment on final occlusion, self esteem and skeletal pattern.

Adolescent treatment

It was clear that the functional appliances reduced the overjets of the patients. Interestingly, removable functional appliances statistically reduced the ANB by 2.37 degrees (95% CI 1.7-2.37). The use of fixed functional appliances did not have a significant effect.

There were minor differences between the Twin Block and other functional appliances.

What did I think?

Because I am conflicted, I cannot comment on the quality of this review. However, it is a Cochrane review and Cochrane operate to a high standard.

When I think about the findings. There are several important points that we should consider. Firstly, the risk of bias tool resulted in the identification of several main problems. This meant that the strength of evidence for the main findings ranged from low to moderate. This is not unusual for a Cochrane review.

I feel that it is important to point out that there was a strong effect of attrition bias. Unfortunately, this is a characteristic of most orthodontic studies because of the length of our courses of treatment and difficulty with long term patient recall. Nevertheless, the problem is there and we need to interpret the findings accordingly.

Perhaps the most important data we found is concerned with the reduction in trauma from early treatment. The strength of evidence was moderate. As usual, with findings of a percentage reduction, we need to remember that even when early treatment was done 19% of the children suffered some sort of incisal trauma. Nevertheless, these are interesting findings.

The adolescent treatment data was also clinically relevant. It is important to look at the effect sizes that we found. For example, removable functional appliance reduced the ANB by 2.4 degrees (low strength of evidence). It is up to you to decide if this is clinically signficant.

My feeling is that we can conclude that functional appliances are effective at reducing overjets and most of this reduction is a result of tooth movement. There is some skeletal change but this is small. We do not grow mandibles with our appliances.


This was a large and complex review that looked at a lot of data and patients. I think that the main conclusions are;

  1. Early treatment results in a reduction in incisal trauma, but it does not eliminate trauma
  2. There is an absence of evidence on any other benefits of early treatment
  3. Adolescent treatment with functional appliances reduces overjets. There are minimal differences between appliances. We do not grow mandibles.



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Have your say!

  1. Does it matter that males and females are lumped together in the trials? Some females are growing like crazy in the ages studies but many males are not. I hope you will address that at Harvard in May.

    • Yes, we can discuss this at Harvard. But if a trial is large enough the effect of gender tends to wash out in the randomisation etc. So it should not make a difference, providing the groups are balanced.

  2. These are great studies, thanks for your contribution to our profession! Since the control group also had Class II treatment, would a more accurate conclusion be, “there is no evidence that the timing of Class II mechanics influences the magnitude of mandibular growth”, instead of saying “we do not grow mandibles”? I believe some findings have shown that early treatment may grow mandibles relative to untreated controls? This has been an area of confusion for me. Thanks!

    • Yes, in effect the early treatment studies looked at the timing of a functional appliance treatment. While there is some difference in ANB in early treatment this tends to be small and not of clinical significance.

  3. I had a discussion on incisor trauma with Dr Proffit and Dr Wheeler. They both disagree with the previous conclusion of an earlier Cochrane review on this topic.
    They explained me that the review seemed to have failed to distinguish cases by the severity of problems, mistaking statistical significance for clinical significance.
    They concluded: UNC and Florida had it right, the Thai guy made a big deal out of weak statistical significance and no clinical significance at all.

    Am J Orthod Dentofacial Orthop. 2011 Oct;140(4):e155-60. doi: 10.1016/j.ajodo.2011.02.023.
    Effect of early Class II treatment on the incidence of incisor trauma.
    Chen DR1, McGorray SP, Dolce C, Wheeler TT.
    Many researchers have examined the prevalence of dental injuries in children and adolescents. The purpose of this study was to examine the prevalence and incidence of incisor trauma in subjects who participated in a randomized clinical trial designed to investigate early growth modifications in the treatment of Class II malocclusion.
    The subjects were randomized to 3 treatment groups during the initial phase of the study: (1) headgear or biteplane, (2) bionator, and (3) observation (no treatment). All 3 groups underwent phase 2 treatment with fixed appliances. Incisor injury was scored at every data collection point with the Ellis index by a blinded examiner using dental casts, intraoral photos, and panoramic and periapical x-rays.
    Twenty-five percent of the subjects had incisor trauma at the baseline examination, and 28% experienced new or worsening maxillary incisor injury during the study. No significant differences were found with regard to sex and prevalence of injury at baseline. No differences in incidence of trauma were found between the 3 treatment groups throughout the study (P = 0.19); however, boys were more likely to experience maxillary incisor injury (odds ratio estimate, 2.37; 95% CI, 1.33, 4.21), and those with an injury at baseline were more likely to experience an additional injury (odds ratio estimate, 1.81; 95% CI, 1.03, 3.17).
    Early orthodontic treatment did not affect the incidence of incisor injury. The majority of the injuries before and during treatment were minor; therefore, the cost-benefit ratio of orthodontic treatment primarily to prevent incisor trauma is unfavorable.

    • This problem arises from the methods of classification of trauma. All studies used a different method. As a result, we decided to go with the simple yes/no classification. This is logical because there could be minimal trauma visible i.e. an enamel crack, but the tooth could be devitalised. The paper that you quoted was a good one but it concentrated on cost effectiveness. I tried to bring this out in my blog post when I calculated numbers needed to treat. While prevention is one thing whether it is worth the cost is another!

  4. We do not grow mandibles. But do we restrain maxillas?

    • Hi Danny, thanks for the comment and there is an absence of evidence that we do anything to maxillas…

      • Kevin:

        You say, “But if a trial is large enough the effect of gender tends to wash out in the randomisation etc.” I think this would only be true if there was no decomposition into shape- and size-change, after correcting for size, since size tends to mask shape differences, such as sexual dimorphism. In fact, I believe geometric morphometrics could also elucidate any differences in mandibular growth, as well as any concomitant effects on the maxilla. For example;

        Singh GD and Hodge MR. Bimaxillary morphometry in patients with Class II division 1 malocclusion treated with Twin Block appliances. Angle Orthod. 72(5), 402–409, 2002.
        Singh GD and Clark WJ. Localization of mandibular changes in patients with Class II division 1 malocclusions treated using Twin Block appliances: finite-element modeling. Am J Orthod Dentofacial Orthop. 119(4), 419-425, 2001.

        I am sure there are other papers of this nature in the orthodontic literature – but I only have these two on hand – best wishes –

      • I seem to remember that Prof. Lysle Johnston has published Class 2 research addressing the effectiveness of maxillary restraint. I could be wrong. Hopefully, Prof. Johnston will weigh in.

  5. Thanks for that Prof
    I have 2 questions
    1 .why you may find that 2.4 reduction in ANB is not clinically significant however that could be enough to change the skeletal base from class II into class I

    2. what do you think about this new protocol
    Thank you

  6. Great review. If the sole benefit is incisal trauma reduction, I would hope that the better comparison group would be use of mouthguards. I wonder if use of removable appliances would create wearer fatigue in such a group as well thereby increasing the incidence of incisor trauma. Theories are easy, the hard work is testing them.

  7. It would be interesting to see if the functional appliance correction stayed the same after all permanent teeth erupted or if some relapse had occurred.

  8. Hi Prof , Do you reckon the conclusion would be different if these trials had included just one type of skeletal pattern? I mean our ability in changing growth potential of mandible might be different in brachyfacial comparing to dolichofacial ? your thoughts?

  9. Kevin, thank you for publishing this material again.

    While claiming to understand the findings of the Cochrane Review on class II treatments,
    Many orthodontists still perform Class II corrections of large class II discrepancies using functional appliances, because they believe that functional appliances are the most effective devices they know for producing the large dento-alveolar changes required to compensate for large Class II discrepancies.
    The practitioners are not claiming that growth is being changed by their treatments.
    They only claim that functional appliances are powerful and effective devices for class II correction.
    After many, but not all of these large Class II discrepancy cases, the orthodontists continue to finish the correction of their class II cases using fixed appliances to produce the fine details of a fully detailed compensated class II treatment outcome. Sometimes by the end of all this, growth has helped them, sometimes not.

    What does an interpretation of the Cochrane Review have to say about this strategy of using Functional appliances as an adjunct to severe class II corrective treatments?

    Thanks for answering this.

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