Summary of functional appliance treatment for Class II malocclusion
In this post I am combining some of my most popular and relevant posts into one post that I hope will summarise the current knowledge of functional appliance treatment for Class II malocclusion. This will start with a brief guide to functional appliance treatment and then I will move on and discuss the research that underpins this important method of orthodontic treatment. I hope that you find it useful
A brief guide to removable functional appliance treatment.
I am joined on this first section by Professor Jonathan Sandler from the UK, who has extensive experience of Class II treatment using several types of functional appliance
As we all know, this type of treatment has been researched extensively and several trials and systematic reviews have been published. I have discussed these in previous blog posts on the results of systematic reviews and the incidence of incisal trauma. I have also discussed that the provision of care should be based on a combination of evidence and clinical knowledge in this post.
We think that the research evidence is very clear on most of the outcomes of treatment. In summary, early treatment, in addition to a later course of orthodontic treatment, compared to a single course of treatment in adolescence, does not have a more favourable influence on: the skeletal pattern, final occlusal result or the need for extractions.
Early treatment does however, lead to a transient increase in self-esteem and there is also weak evidence that it reduces the incidence of incisal trauma. One decision that we need to be make is whether the child’s self-esteem is in need of a boost at this stage or whether, bearing in mind the downside of doing two courses of treatment in terms of cost to the patient, the parent or the state, it would be better to wait until definitive treatment can be performed in one phase at a later stage.
When we consider the risk of trauma we need to evaluate if the child is at risk because of their general activities.
As a result, we feel that early treatment should not be routinely prescribed for patients with large overjets, but may be considered if one of our patients is either being harmed due to excessive teasing at school, or has a sufficiently large overjet (or lifestyle) that we feel makes them at a serious risk of significant trauma.
Patients in the late transitional or early permanent dentition with moderate overjets (6-10 mm) often with a moderate skeletal discrepancy.
We feel that, again, this decision is clear and we have a high level of certainty. We would tend to treat this group with a Twin Block. For the following certainties that are derived from our study into the effectiveness of Twin Blocks vs Herbst.
- There is a a rapid correction of the overjet in most patients
- Co-operation is reasonable, with a non-compliance rate of 30% in the UK.
- They are much less expensive than the Herbst appliances
- They are significantly easier to manage when problems occur
- The transition from the Twin Block to fixed is straightforward.
We know that this appliance will reduce the overjet, mostly by tipping of the teeth but it will not change the skeletal pattern to a clinically meaningful degree (although, occasionally we ‘strike lucky’ and see patients with very favourable mandibular growth). Importantly, we cannot predict those patients who are going to grow well and those whose teeth will purely tip.
We think that it is important that we inform patients that the evidence shows that their facial skeleton is not going to change significantly but we will certainly correct their appearance, if they co-operate with treatment.
Patients with a severe overjet and skeletal discrepancy.
This is where we have most uncertainty, and this is reflected in the comments that were made on the previous post. We are now faced with a genuine dilemma.
- Treat them now with the main aim of reducing the overjet and the overbite with a combination of upper and lower incisor tooth movement and accept that this will leave the child with a (camouflaged) skeletal discrepancy.
- Avoid treating now and wait until the patient has stopped growing and then provide definitive orthognathic treatment to fully correct the overjet and overbite as well as the skeletal discrepancy.
If we consider these options:.
The advantage of option 1 is that we will correct the overjet, overbite and sometimes the transverse problem (Figure below). This improvement in dental appearance as well as the associated soft tissues, during the formative adolescent years, may have benefits in self-esteem (although research evidence is lacking). We could argue that as this is a critical time in a child’s life when they learn most of their interpersonal skills. With the possibility of improved appearance they maybe happy to accept that their skeletal discrepancy is still present albeit in a much less noticeable form.
The disadvantage is that while we can attempt to correct the overjet, the patient may still be unhappy with their final facial appearance and they may request orthognathic surgery later. This will, mean undoing the dento-alveolar compensation that we achieved in our earlier course of treatment which might add an extra 6 months to the fixed appliance phase of treatment. Furthermore, in severe cases where camouflage is attempted we may run the risk of over proclination of the lower incisors and compromise gingival health.
The advantage of option 2 (surgery)is that we can correct both the dental and skeletal discrepancy in one course of treatment. Theoretically, there should be less uncertainty with this approach.
The disadvantage is that we will leave these impressionable teenagers during their formative years with a substantial malocclusion.
What is our solution?
Our feeling is that the solution to our dilemma involves explaining all of these uncertainties to the patient and their parents. This means that they will then be aware of all the risks and benefits of each approach to treatment. They can then play a very active role in reaching the important decision of how to proceed.
Other areas of uncertainty.
While we feel that we have outlined sensible approaches to these clinical problems, there are still some other uncertainties. One of these is whether using fixed appliances and some form of Class II mechanics, whether it is a fixed Class 2 corrector or headgear and class 2 elastics, will result in a similar result to a course of functional appliance therapy. As some people argue that functional appliance treatment is simply a method of applying Class II traction. Our feeling is that we do not know for certain and it may, therefore, be useful to carry out a trial in this area.
As things stand, we would prefer to use Twin Blocks, on most patients with large overjets, presenting in the early adolescence mostly because we are confident that we can achieve our desired result with a functional appliance providing the patient will cooperate with treatment.
Let’s now move to some of the evidence.
Research Evidence on Functional Appliance treatment
Which are best? Fixed or removable functional appliances….
It is now many years ago that we carried out a multicentre trial that compared the Herbst and the Twin Block appliance. This can be found here. I was also one of the operators in the study and I learnt a lot about using fixed functional appliances. My personal experience was that the Herbst appliance was very effective but the trade-off was that we had major problems with breakages. As a result, several years later, my preferred appliance is still the Twin Block. This is my personal opinion reinforced by the results of our trial, but what does this new review tell us?
EJO Advanced publication. DOI: 10.1093/ejo/cjv086
This is another publication from the team at Queen Mary University, Whitechapel, London, South of England. Unfortunately, it is behind the impenetrable paywall of the European Orthodontic Society…
This was a nicely written paper. I thought that the literature review was particularly good and I recommend that anyone on a training programme should read this as it provides a great outline of functional appliance treatment. In addition to outlining the various advantages and disadvantages of the types of functional appliances the authors also pointed out that we need to move away from purely morphological measurements and include patient perspectives. I have covered this subject previously another blog posts.
Their objective was to provide evidence on the efficacy of fixed and removable functional appliances in terms of both morphological and patient centred outcomes and I felt this was very important.
What did they do?
They carried out a systematic review to high standards and they clearly stated the PICO.
Participants: Children less than 16 years old with Class II malocclusion
Interventions: Any type of fixed functional appliance
Comparison: Any type of removable functional appliance
Outcome measures: The primary outcomes were measures of skeletal, dento alveolar and soft tissue correction.
This review was carried out to a high standard as they only included randomised or nonrandomised trials. All the studies had to be prospective. It is important to work to this high level of selection criteria because this reduces the chance of selection bias that is inherent in retrospective investigations.
After their screening and application of selection criteria they identified four studies. They evaluated these studies with the Cochrane Collaboration risk of bias tool and provided a large amount of information on potential bias. They concluded that three studies were at high risk of bias and one was unclear. The most common reason for this allocation was unclear randomisation and allocation concealment.
I find it interesting that one of the studies they classified as “high risk of bias” was the Herbst vs Twin Blocks study that I carried out. In this study we reported that we had a greater dropout rate in the Twin Block group than the Herbst group. As a result, the authors classified study as being at high risk of bias. This is the correct conclusion from applying the Cochrane tool. However, it is important that this does not diminish one conclusion from our study in which we found that there was better cooperation with the Herbst appliance than the Twin bBock. Putting this aside, I will never forgive the authors for this classification!
More seriously lets look at what they found.
What did they find?
Firstly, two of the studies compared with the Twin Block and the Herbst appliance while the other two compared the Activator with the Forsus and the TFBC appliance. It was not possible to combine the data into a meta analysis because of differences in measurement between the studies. They did provide a lot of detail of relevant cephalometric measures that showed the effect of the appliances on dento alveolar and skeletal measurements (which were small). They concluded that all the variations of functional appliance successfully reduced the overjet to normal limits. There were also minor skeletal changes but as these were not compared to an untreated control group. We cannot, therefore, make any conclusions on whether the appliances changed the skeletal pattern more than normal growth.
They also stated that they were disappointed at the limited use of patient centred measures. They drew attention to our study in which we measured breakages and patient acceptance of the appliance. They also pointed out that our findings would have been viewed very differently if we had drawn greater attention to them in our paper. I completely agree, if I had my time again I would have emphasised the patient centres measures more. For example we showed that the Twin Block had a greater negative affect on speech, sleep patterns and schoolwork and the length of the treatment was longer than with the Herbst. Yet there were greater breakages with the Herbst appliance and it was more expensive. This information should be very useful when we are deciding on potential treatments with our patients.
What did I think?
I feel that this review does add to our knowledge, despite the limitations of the number of papers. I can conclude the following.
- There is little difference in the dental and skeletal effects of fixed and removable functional appliances.
- Most of the correction of the overjet is by dento alveolar movement, but there is a small amount of skeletal change (1-2mm).
- There is greater co-operation with fixed functional appliances but this is not 100%. There is no such thing as non compliance orthodontic treatment!
- Only one study reported on patient centred outcome and these should be included in all trials in addition to some cephalometric and dental measurements.
I will still stick with the Twin Block because of the cost and the additional time that is needed to deal with breakages with a fixed functional appliance.
I did this post with Badri Thiruvenkatachari, who has worked with me for several years, and was the lead author on our updated Cochrane Systematic Review, on the treatment of Class II malocclusion.
This can be accessed on http://goo.gl/puzQR5. This is one of the largest and most cited orthodontic Cochrane Reviews and was first published in 2007. One of the requirements of carrying out a review for Cochrane is that you have to commit to update the findings periodically. This means that as new knowledge from studies becomes available, this is included into the reviews. In effect, the review is a “living document” and the conclusions may change with time. This is one of the great advantages of Cochrane reviews compared to the more static conventional literature. The downside is that you are committed to updating your reviews for as long as you are working!
This update allowed us to include several new studies and evidence that has become available. It also resulted in several of the established studies being reassessed for the quality of evidence, and new statements made on the strength of evidence in the review.
So what did we find?
The review included 17 studies with data derived from 721 participants.
- Three trials compared early treatment with functional appliances (2 Phase) with treatment provided in adolescence only (1 Phase).
- Two trials compared early treatment with headgear to one phase adolescent care.
- Six trials compared different types of functional appliances when used in one phase adolescent treatment.
- Finally, one trial compared treatment with functional appliance against no treatment
What did we conclude?
I found it very interesting and important to find that adding newly available data resulted in a change in the conclusions from the first version of the review. This was relevant to the role of early Class II treatment in preventing incisal trauma Our overall conclusions were
“providing early orthodontic treatment for a child with Class II malocclusion is more effective in reducing the incidence of incisal trauma than providing one course of treatment in adolescence. There was no other advantage in providing early treatment”.
“When one course of treatment was provided in adolescence, no functional appliance was better than another. Any change in skeletal pattern when compared to a control was not clinically significant”.
It was also important to consider that the overall quality of evidence was low, apart from the findings on trauma, where the quality of evidence was moderate. This may be interpreted by considering confidence in the results. So where evidence is low quality, this may be defined as “further research is very likely to to have an important impact on our confidence in the findings’. When the level of evidence is moderate this means that “further research is likely to have an important effect on our confidence”. I have discussed this issue of confidence in a previous blog post. Sense about science: Dealing with uncertainty in orthodontic research.
How strong are the conclusions for Class II orthodontic treatment?
If I build on my post of last week. It is clear that when we consider most of the findings of this review, we must appreciate that the quality of the evidence is low because of bias in the studies. We also need to remember that Cochrane is pretty unforgiving in this assessment! The reasons for this classification are clearly stated in the review and I shall address this assessment in a future post.
Nevertheless, when we consider the important findings on trauma, we can have some confidence that this is a clinically important finding. At this point, we should examine the data concerned with the potential reduction in trauma. This data is shown in the paper in the summary of findings table 1 for the main outcomes. This reveals that 29% of patients with new trauma were in the 1 phase adolescent treatment group compared with only 20% of those patients receiving early treatment. The odds ratio was 0.59(CI 0.35 to 0.99). This is a clinically significant finding, but we need to appreciate that the CI is wide and almost contains 1. We also need to consider how to interpret the odds ratio. As with several statistical tests this is not straightforward and I had to look this up. I found this explained well in this blog http://goo.gl/lDWlI8. They explain odds ratio in this way…
“When you are interpreting an odds ratio (or any ratio for that matter), it is often helpful to look at how much it deviates from 1. So, for example, an odds ratio of 0.75 means that in one group the outcome is 25% less likely. An odds ratio of 1.33 means that in one group the outcome is 33% more likely.”
If we now look at the OR we found (0.59) this means that in the early treatment group (functional appliance) the chance of trauma was 41% less likely than for the group whose treatment was provided when they were in adolescence.
So what does this mean clinically?
Whenever, I give a course or speak to trainees, I stress that one we have read a paper we need to consider the “so what” question and whether we are going to change our practice based on the results of the study. It is clear from this review that moderate level of evidence suggests that providing early Class II treatment with functional appliances reduces incisal trauma. This means that when I see an 8 year old child with an increased overjet, I will explain to them that early treatment will result in a transient increase in their self esteem and that they will be 40% less likely to have trauma than if we waited to provide treatment when they are older. They can then decide. I suspect that we will be providing more early treatment…
Removable functional appliances do not change the skeletal pattern to a meaningful degree
It appears that the journals are publishing more and more systematic reviews. This review was on the effects of removable functional appliances on the skeletal pattern.
Vasilis Koretsis et al
EJO 2014, 1-7. Advanced access
What did they want to do?
The authors aimed to assess the effects of removable functional appliances in treated vs untreated patients using outcomes from radiographs. Bearing in mind my comments about radiographs and research, I did start reading this paper with a degree of trepidation, as I feared that I was entering a morass of cephalometrics. However, I was pleasantly surprised and I thought that this was an interesting and relevant review.
When I started reading I did become concerned because they did not confine the review to RCTs and included prospective non-randomised controlled clinical trials. As a result, we need to bear in mind that this is not as high a level of evidence as a Cochrane review, which only includes randomised studies. However, reviews of this nature do have a place, as long as we remember this shortcoming and interpret them accordingly.
What did they do?
They outlined their methods in a very clear way. It was good to see that they carried out a quality assessment of the literature that they included. They did this by assessing the RCTs with the Cochrane risk of bias tool and the CCTs with a similar instrument. They finally used the GRADE methodology to evaluate the overall strength of evidence from the review.
What did they find?
They included 17 studies and these were divided up into 7 RCTs and 10 CCTs. They carried out a series of planned meta-analyses. These were clearly set out.
They concluded that when the effects of removable functional appliances were compared to no treatment, the following differences occurred
|Variable||Mean Change/Year(Degrees)||Confidence Interval|
They also found that the Twin block was the most effective appliance, when compared to others.
The strength of evidence according to GRADE varied from moderate for SNA change to very low for ANB change.
They finally concluded that the skeletal effects of RFAs are minimal and of negligible importance. Most of the change was dental.
What did I think?
I thought that this was an interesting review that came to good sensible conclusions. I was a little concerned about the inclusion of CCTs, particularly when there was an adequate number of RCTs to draw some conclusions. However, they did report this in sufficient detail for the critical reader to interpret the evidence that they presented.
I did disagree with one of their conclusions when they stated that “more research is needed”. I cannot help thinking think that we have enough research from trials and systematic reviews to conclude that
“WE CANNOT GROW MANDIBLES OR RESTRICT MAXILLARY GROWTH TO CORRECT SKELETAL DISCREPANCIES WITH REMOVABLE FUNCTIONAL APPLIANCES TO A CLINICALLY MEANINGFUL DEGREE”.
I actually think that it is time to move on…….I now wonder whether it is necessary to carry out any more studies on the cephalometric effects of removable functional appliances. This review systematically covers a large amount of the published literature and it pretty much says it all….
Can we say the same for fixed functional appliances? I have seen no reason to say otherwise…
Does this finding help us in practice, when we see a patient with a Class II malocclusion. If the skeletal discrepancy is mild to moderate then I would be fairly certain that if I used a functional appliance I could obtain a good result from a combination of dental movements and some favourable growth. But what if the skeletal discrepancy is severe? I think that I would treat with a functional, but I would warn the patient and parent that they will still have a skeletal problem and this may need surgical correction in the future.
Do functional appliances influence skeletal pattern? More reviews giving us the answer!
In the final section of this summary I’m going to review two systematic reviews on functional appliances. Both aim to identify skeletal effects of functional appliances.
Ishaq et al
AJO-DDO Volume 149, Issue 5, Pages 612–624
These investigators carried out a systematic review to evaluate the effect of fixed functional appliances combined with multi bracket appliances on class II skeletal pattern.
What did they do?
They carried out a systematic review of articles published until April 2014. They included papers reporting randomised clinical trials and non-randomised controlled clinical trials. Each study had to include an untreated control group. Their main outcome measure was cephalometric data collected at the end of the functional phase of treatment.
They assessed risk of bias with the Cochrane tool for RCTs. They used the Newcastle-Ottawa scale to assess the quality of the non-randomised studies.
They initially identified 1366 papers and after the usual filters they identified 5 trials. These were divided into 1 RCT, 2 quasi RCTs and 4 prospective controlled trials. There was some variation in the measurements used in the studies, nevertheless, they did extract data on relevant measurements. This data was not presented in the table and I found it a little difficult to follow.
In summary, they showed that the use of fixed fractional appliances when combined with multi-bracketed appliances did not have an effect on the skeletal pattern. However, the evidence was weak.
Nucera et al
This was a paper from a team based in Italy and Greece.
What did they do?
They carried out this systematic review to find out if there was an effect of removable functional appliances on maxillary growth.
They included studies that were randomised controlled trials and prospective controlled clinical trials that included an untreated control group. Again, the outcome measure was cephalometric measurements.
They carried out the usual search, filtering and assessment of risk of bias. They finally identified 14 papers. These were divided into 4 RCTs and 10 prospective CCTs.
What did they find?
They found that the main effect of functional appliances on the maxillary restraint was -0.61° per year. This was statistically significant. But my feeling is that this was not clinically significant
They also found that there was a mean difference of -0.61 mm in anterior maxillary displacement. There was no effect on maxillary rotation.
In the discussion they pointed out that they only found a small number of trials and this led to a large amount of variation in the data. Nevertheless they did conclude that removable functional appliances appeared to inhibit sagittal maxillary growth.
What did I think?
A few weeks ago I covered another systematic review on the effects of functional appliances on skeletal growth. You may remember that this was on the effects of fixed function appliances and the authors concluded that there was no influence on the skeletal pattern to a meaningful degree. It is interesting to see that these two papers have reached the same conclusion.
In the comments section of one of my previous posts Carlos Flores-Mir pointed out that in the last 10 years there have been 25 systematic reviews on class II treatment. He also felt that the most important findings from any trial should be concerned with factors such as compliance and patient experience. I totally agree with him.
The authors of both of these papers made the “usual” conclusion to a systematic review that “more RCTs were needed”. I am not sure that I agree with this statement as it is now becoming very clear that functional appliance treatment does not influence cephalometric measures to a clinically important degree. Nevertheless, I think that if further trials are to be carried out investigators should evaluate other outcomes such as compliance, experience, socio-psychological factors, trauma and even breathing. These are far more important outcomes that are relevant to our patients.
I cannot help feeling that we are in danger of carrying out too many systematic reviews into Class II malocclusion based on cephalometric measurements. There appears to be a trend to review the effects of every individual functional appliance on every different facial bone! I am worried that we will soon be having systematic reviews of systematic reviews in the endless quest to find out if we can alter facial growth.
At this point I’m sure that the question has been answered. I will also not write another blog on a systematic review on the effects of functional appliances.
Finally, I will make a plea to investigators and Journal editors. Please make this stop….. and I do not think that CBCT will tell us any more than we know now!
Summary: What do we know about functional appliances
I would like to provide a summary of these posts that is fairly clear and straightforward. I hope that it is useful
- There are limited advantages to providing early orthodontic treatment of Class II malocclusion. However, there may be reduction in the incidence of trauma. Early treatment could also be provided to reduce teasing and bullying, but only if a child is being teased or bullied.
- Most of the reduction in overjet is achieved by tooth movement. There is minimal skeletal change and this cannot be predicted.
- When we provide treatment in adolescence there is nothing wrong with extracting upper first premolars and reducing the overjet. This treatment is practiced all over the world in countries where functional appliances are not so extensively used.
- There are no differences in the treatment result of fixed and removable functional appliances
- There is greater patient co-operation with fixed functionals than removable
- The Twin Block is the most popular functional appliance in the UK.
- There is no point in putting on or leaving off the labial bow on a Twin Block.
- If headgear is used to “drive Class II molars distally” the average length of the “drive” is 1.6mm
- No one can grow a mandible!