April 18, 2016

Fixed functional appliances do not make mandibles grow: Another massive systematic review of cephalometric data

Fixed functional appliances do not make mandibles grow: Another massive systematic review of cephalometric data..

A few weeks ago I posted on a systematic review of Class II treatment and concluded that functional appliances do not have a clinically significant effect on skeletal pattern. This new post is on another systematic review which investigated the treatment effect of fixed functional appliances.

Screen Shot 2016-04-18 at 11.52.34Treatment effects of fixed functional appliances in patients with Class II malocclusion: a systematic review and meta-analysis.
European Journal of Orthodontics, (May 2015), 1–14. doi:10.1093/ejo/cjv034
Zymperdikas, V. F., Koretsi, V., Papageorgiou, S. N., & Papadopoulos, M. A.

What did they do?

This was a standard systematic review based on Cochrane collaboration methodology. It is worth pointing out that this was not a Cochrane review. The authors use the following eligibility criteria to include/exclude publications

Difference between treatment and control95% CI

They carried out all the usual steps of a high quality systematic review. After the literature research, they identified nine studies for inclusion. They evaluated risk of bias with the Cochrane Tool for risk of bias and the GRADE approach. They summarise the data and carried out a meta-analysis of many cephalometric variables.  They had intended to analyse other outcomes that were more important to patients, but they could not find any.

What did they find?

They reported in detail on 24 cephalometric variables. I am not going to outline all of these (thank goodness I hear you cry!). But I have selected a few that I think are important and included them in this table.

If we look closely at this data it is clear that the skeletal change (ANB) is small and probably not clinically important. However, the dento-alveolar changes are much greater.

When I looked at the 95% confidence intervals for skeletal change (ANB) I found that this could be as little as -0.98° or as great as -2.5°. This represents some uncertainty and small treatment effects.

What did I think?

I felt that this review provided information that reinforced other reviews. They came to the same conclusion; functional appliances do not influence the skeletal pattern to a meaningful degree. It appears that they correct the overjet by tipping the lower incisors forwards and retrocline the upper incisors.

I think it is also relevant to point out that five of the nine studies involved a comparison with a historical control group. As a result, we need to interpret this data with a degree of caution because the selection of historical control groups may introduce bias. I have discussed this before.

I cannot help thinking that the question of whether functional appliances influence skeletal growth has been answered. They don’t have a clinically significant effect.

Finally, I also wonder if it is time that we stopped investigating the effect of functional appliances on cephalometric variables. We need to evaluate other far more relevant outcomes, for example, patient perceptions of the appliances and maybe breathing etc? to this end I have decided not to do another post on a cephalometric study.

Time to move on… There is nothing to see here

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Have your say!

  1. I do agree that with the amount of systematic reviews and meta-analysis about Class II malocclusion treatment management published lately (around 5 last year and over 25 in the last 10 years or so, not considering surgical approaches) there is clarity regarding the lack of clinically meaningful effects at skeletal level. There are factors that likely confuse the effects. For me two important ones are the time required to start seeing effects that may be considered clinically significant (24 or more months in treatment) – most studies report changes in the 6-12 month of treatment range) and the lack of proper differential diagnosis (vertical growth type, initial dental/skeletal positions – we seem to group everything together). This may mud the water, but unlikely to convert a patient that may benefit skeletally from a surgery only using functional appliances. Factors like patient compliance, patient’s experience with appliances, time required to achieve the results are the real clinical questions. Thanks Kevin. Carlos

  2. Wouldn’t new 3D xrays be interesting to see? If the dose is low enough, perhaps creating new longitudinal growth studies, maybe even put in a a super mini TAD long-term or something to index off of?
    Maybe off the kids free braces when it’s time for the hassel. And then do some functional appliances and see the true growth? Is there value there?

  3. Thank you for continuing to clarify this issue! I agree this question seems to be answered but I also realize there are still many that disagree. Also, thank you for using the facts (rather than emotion) to argue your points.

  4. A lot of people have too much invested in functional appliances (money, ego, credibility, and yes, money) to ever accept the truth.

  5. I´m agree. And also, functional appliances have a better effect in soft tissues.. and thats why people feel confortable with them.

  6. This sort of gives the MaxFac surgeons something to smile about.

    If we accept that these appliances don’t have much skeletal effect, can we start to find out if they have much effect on overjet (which is a typical patient complaint and a dental health feature) or buccal segment relation and occlusion? I think those are reasons that a lot of orthodontists use functional appliances.

    And does a fixed functional work better than a removable functional on average just due to compliance?

  7. Is it possible that when you have big data sets and average out the values you loose the ability to see subgroups of patients who are excellent, average and poor responders to functional appliances?

    • Thanks for the question. You are correct that the big data approach will evaluate the mean effect of any treatment and this is what we really need to find and understand. All trials measure the mean effect of a treatment carried out on an average population. However, if the data set is large enough then other analyses can be carried out to identify the characteristics of good responders. We tried that on our large Class II studies, but we could not find any predictors of good response

  8. What is the definition of “functional appliances” used in this study?
    I believe these types of studies tend to reinforce stereotypes/myths without actually getting to the ‘truth’ of the matter – in the sense that 2D cephalometric analysis is far from the truth.
    If surgical techniques can ‘grow’ the mandible, then what is the mechanism of that growth? Obviously, the answer resides in a viable stem cell population(s). However, if that stem cell population resides in the mandible/condyle a priori, then who is to say that a sub-population cannot be targeted using an epigenetic approach?

  9. Thanks for your post! Another solid piece of evidence that we cannot grow mandibles with functional appliances. Why are we so reluctant to recommend mandibular advancement surgery? I, of course, am extremely biased.

  10. My concern with Fixed functional appliances is that they do not, by design, address the maxilla properly. Since we know that the maxilla is as often retrusive in Class II cases, why would we want to use anything that uses the maxilla as anchorage? At very best – and the literature attests to this – you get half of whatever correction you get by moving the maxilla back even further. And the mandible can only come halfway to a retrusive position. No wonder we can’t get results.

    An ideal approach would be to first put the maxilla back where it belongs, ie: forward toward the front of the face, and then move the mandible all the way forward to where it should be as well. If you can do this without using the maxilla as anchorage, maybe we could see some statistically significant results.

    • Thanks for the comment.How do we make the maxilla move forwards? Have you any proof that this can be done?

      • Only 25 years of experience using appliances which develop the maxilla both laterally and sagittally, ie:
        Biobloc stage 1, Harry Orton’s ELSA, the ALF, Myobrace + Bent Wire System, Clark Trombone Appliance. Correcting the retrognathic maxilla has to be the first goal of treatment before translating the mandible forward to a stable result. My private orthodontic practice was in the town of Haslemere, Surrey and my practice was built on word of mouth. Parents frequently brought younger siblings for treatment following what they felt to be successful treatment for their older child.

  11. Hi Dr. Kevin,

    Probably this mistake is made by many…including me to convince the parents n to reinforce the wearing of functional aapliance …. Probably from next time will refrain from using the term jaw growth modulation and concentrate more of patient concern of prominent teeth and their correction…..
    I just have one doubt… Let’s say a 11 yr boy with peak growth spurt retrognatic mandible…chief complaint ..prominent upper tooth…Angles full cusp class 2 overjet 10mm and positive vto ….now what 3 option (functional; fixed functional; start aftr puberty and extraction)would you suggest to parents in order of your preference and why.

    P.s. I will mail you one such case which I treated with twin block….got decent results ….it was difficult for the parents to convinc for twin block initially ….total treatment time was 28months…. Would like to know your view on this .

  12. I saw they reviewed all types of fixed functional appliances, including forsus which just pushes the teeth, it doesn’t bite jump like the herbst or mara. Appliances that dont bite jump shouldn’t be able to make a difference skeletally.

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