A sensible guide to removable functional appliance treatment?
This weeks post is a summary of the evidence behind the use of removable functional appliances. It is an update of an earlier post in 2014.
I am just back from the AAO meeting in Los Angeles. At this meeting, I saw several presentations on the use of growth modification appliances. As usual, presenters made claims about growing mandibles and improving breathing. As a result, I thought that it would be a good time to revisit some of the basic information on the correction of Class II problems with removable functional appliances. I am also massively jetlagged and I cannot write a new post today!
I published the original post on this method of treatment in December 2014.
My colleague and friend Professor Jonathan Sandler worked with me on this post. We will divide this up into several main areas.
As we all know, this type of therapy 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 . I have also explained that the provision of care should be based on a combination of evidence and clinical knowledge in this .
We think that the research evidence is unequivocal 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 evidence that it reduces the incidence of incisal trauma.
We, therefore, need to make an important decision on whether the child’s self-esteem requires a boost at this stage or if 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 may put them at 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 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 significant 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 essential that we inform patients that the evidence shows that their facial skeleton is not going to change significantly, but we will undoubtedly correct their appearance if they cooperate with treatment.
Patients with severe overjet and skeletal discrepancy.
This is where we have the 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 adequately 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. 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 may be 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 means 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 critical 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. 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 sure 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.
In summary, we feel that the evidence for the treatment of Class II malocclusion is available and can be readily interpreted. This is a mixture of the “art and science’ of orthodontic care. It is essential to remember however that despite being able to improve appearance significantly we just cannot grow mandibles!
Emeritus Professor of Orthodontics, University of Manchester, UK.