December 16, 2019

Long term effects of eruption guidance look impressive?

The use of myofunctional/eruption guidance therapy is one of the most exciting areas in orthodontics.  This new long term study about this treatment surprised me with its results. This is because they potentially intercepted 100% of developing Class II malocclusion. As a result, I thought that I should have a close look at it in this post.

It is now well established from previous randomised trials that early orthodontic treatment for Class II malocclusion, provided in the late transitional does not offer many advantages.  However, one of the criticisms of the large scale trials is that treatment was provided at the time of slow facial growth.  This led to suggestions that treatment early treatment should be done when children are younger at approximately 5 years old.  Furthermore, there may be a role for using pre-formed eruption guidance appliances in this age group.  

There have been a few trials into the use of this type of appliance. I think that these are interesting and there may be potential in this form of treatment. However, further research is needed for us to adopt these more widely.  I was, therefore, really interested to see this new paper that the European Journal of Orthodontics published.  A team from Finland did this study.

Class II treatment in early mixed dentition with the eruption guidance appliance: effects and long-term stability.

Katri Keski-Nisula et al  EJO Advanced access.  doi:10.1093/ejo/cjz092

I think that the author has made a pdf of their paper available on Research Gate.  

This paper reports a subset of data from a large scale study on the effects of early treatment with Eruption Guidance Appliances (EGA).  They have published articles on this before, and I have discussed one study recently.

What did they ask?

They did this study to ask this simple question:

“What are the occlusal and skeletal effects of Class II treatments that were carried in the early mixed dentition with an Eruption Guidance Appliance”?

What did they do?

In this paper, they report on a group of patients with Class II malocclusion.  I thought that it was worth going into this in some detail, as it is a bit tricky to follow.

They started this prospective cohort in the mid-1990s.  The participants were children who were born 1992/3, living in three rural communities in Finland.  They offered children with malocclusion who lived in two of the villages early eruption guidance (EGA) treatment. The children who lived in the other town were not provided care, as this was the practice for this town. This group acted as the control.

They used these inclusion criteria for the Class II sample of participants.

The distal step was equal to or larger than 1mm or Class II canine relationship equal or larger than 2mm.

They examined all the children at the beginning of treatment (T1) and at the end of the early mixed dentition period (T2).  Then they followed those in the early treatment (EGA) group until their 17th birthday (T3).  They provided early treatment from T1 to T2. The participants wore the appliance every night and then then it was used a retainer for two nights a week.

They examined the control group of children at T1 and T2. They all received treatment in the middle mixed dentition. However, they did not look at them at T3.  This is important, and I shall return to this later.

They recorded the following data:

  • They measured overjet and overbite directly in the mouth.
  • Other dental measures, for example, crowding/spacing, Class II were measured from study casts
  • Finally, they did an extensive cephalometric analysis.
What did they find?

To understand this study, we need to look carefully at the flow of participants.  They set this out very nicely in a flow chart. I thought that this was relevant data.

  • 315 participants with malocclusion were identified. 50 declined treatment or were treated by other interceptive methods.
  • 255 started treatment with EGA.  Then they selected a Class II subgroup of 115 children (according to the criteria that I mentioned above).
  • Of this group, 8 moved away, 23 were non-compliant, and for 19 the parents were concerned about the “effects of the appliance material”.
  • This left a final sample of 65 participants who attended T2.  This is a drop out rate of 44%.

When they looked at the process of treatment, the mean age of the treated group at T1 was 5.4 years, and the control group was 5.1 years. At T2, the treatment group was 8.5 years old, and the control group was 8.4 years old. This meant that the EGA treatment was approximately 3 years duration.

They provided a large amount of data, and I thought that these were the most important findings.

  • The mean overjet of the treatment and control groups at T1 was 3.4mm. At the end of T2, it was 2.2mm for the treatment and 4.7mm for the control. At T3, the overjet for the treatment group was 2.1mm.
  • The frequency of Class II decreased in the treatment group from 100% to 14%, Whereas, in the control group, it reduced from 100% to 78%.
  • In the maxilla between T1 and T2, there were no differences between the groups
  • Mandibular length increased by 11.4mm in the treatment group and 6.4mm in the control group.  This was statistically significant.  This continued between T2 and T3.  As a result, the best time to carry out growth modification treatment may be the early mixed dentition.
  • The early intervention group did not require any further treatment.

Their overall conclusions were:

“Early Class II treatment with the EGA resulted in significant dental and skeletal effects. These appeared to be stable. As a result, the early intervention eliminated the need for the second phase of treatment”.

What did I think?

I thought that this was a large, complex and ambitious study.  I have done some long term ortho studies, and these are difficult to do, and I would like to congratulate the authors.  It appears that this is another study that suggests that myofunctional appliances may have a role to play in orthodontic treatment.  However, we need to look at the study very carefully, and I hope that I have highlighted this clearly.  

If I am to be very critical, I would like to point out the following.

Firstly, this was not a trial; it was a prospective cohort. As a result, there is likely to be more significant bias than in a well-conducted RCT.  This is evident when we consider that the treatment group was comprised of 38 girls (58%) and 27 boys. Whereas, the control group had 26 girls (44%) and 32 boys. As a result, the groups were not balanced for gender.  This could have influenced the results, particularly concerning facial growth. Importantly, they did not take this into account in their statistical analysis. In fairness to the authors, they pointed this out in their discussion.

I was also a little concerned that even though this was a Class II sample of patients the mean overjet at the start of treatment was only 3.4mm and even after three years of treatment this was reduced to 2.2mm.  These are small changes for such a lengthy procedure.

Furthermore, we need to consider whether this treatment was efficient.  We can decide on this by looking at the completion rate of treatment.  It appears that 42/115 (36%) of the patients did not complete. While this is similar to some other functional appliance studies, we also need to factor in the small amount of overjet change.  As a result, I wonder if these small treatment effects and high non-co-operation rate justify the considerable burden of a three-year treatment.

I was particularly impressed with their conclusion that none of the early treatment group required a second phase treatment.  Importantly, all of the control group received conventional treatment.   It appears that the choice for patients is three years of EGA treatment or some sort of traditional treatment when their permanent dentition erupts.

Unfortunately, there were no comparisons between the treatment effects and process at T3. I may have missed this, but this is a critical factor when we want to evaluate the impact of a treatment.

Final thoughts.

When I have considered all these factors. I still think that this was an interesting and well-done study.  It does provide us with some interesting information. Unfortunately, I am not sure that this is sufficient to result in a change in practice. However, it is a clear pointer to further research.  I think that there may be something to eruption guidance/myofunctional treatment, but we still need trials in this area before it should be widely accepted.

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Have your say!

  1. As noted the change of around 6 mm in three years in mandibular dimensions over the control group changes is likely the most clinically significant change. This difference would account of about 2mm/year which is similar to what has been reported for changes during pubertal growth. This in itself opens the door for clinicians to consider early management of mandibular deficiency problems. Again talking about removable devices drop outs are a problem we will have to face.
    The potential cost of these removable devices is minimal compared to custom made ones which is a plus. It appears that the dental malocclusion degree was very mild so the reported changes in this regard are not what is most impressive.
    Finally, a clinically pertinent question rises when the magnitude of the deficiency is 10 mm. Is 5 years of full time use of an orthodontic appliance “better” than surgical intervention? The key here is informed consent process. Such question is for the parents to decide when faced with proper unbiased information. Not all would decide in a specific way. There is a psychological impact of lengthy interventions to be considered.

  2. Dear Prof.O’Brien

    Thank you for your fair and critical analysis of this paper.

    Per your mentioning,’….another study that suggests that myofunctional appliances may have a role to play in orthodontic Treatment.’, please consider:

    I am curious about how certain other aspects of myofunctional factors/principles might also be utilized in the primary/early mixed dentition to help us better understand not only how to best Tx malocclusion, but also how to maybe prevent and/or mitigate developing malocclusion severity. Subtle ‘malocclusion phenotypes’ (e.g., high/narrow palatal vaults, MTD, maxillo-mandibular retrusion, hyperdivergent vertical growth sensitivity, etc.) that are known to often be co-morbid with sleep-breathing problems (e.g., chronic nasal disuse, snoring,OSA, parasomnias, etc.) are usually first detectable in very early childhood…..and thus might then be acted upon….this has been in the published medical and dental literature for over a century (RP Rogers 1922 Cosmos 64(7):711-‘Making Facial Muscles Our Allies’). Granted, Dr. Rogers’ early published work was not based upon prospective and blinded RCT’s (Sorry Nicky) but rather were based mostly upon controlled ‘observational’ study design….as was pretty much all research prior to the first published RCT in 1944-LANCET(reference upon request) and the War Crime Trials at Nuremberg.

    What you have published today I think will generate much needed curiosity amongst your most critically-thinking followers and I am grateful to you sir for this critical and fair analysis.

  3. Three years of treatment to reduce the mean overjet by 1.2mm to 2.2mm, with a third of patients dropping out. Or reducing the overjet by 1.4mm in the control group to 2mm. But more mandibular growth in the treatment group? Something does not add up!

    None of the treatment group needed any further treatment?? No crowding, crossbites, deep bite…. Hmmm

    And I don’t believe in the tooth fairy

  4. It would be useful to know what criteria was used to determine that the test group did not require a second phase and who made that decision. That kind of result is extremely unlikely for any treatment modality. Was there by chance any funding by a manufacturing corporation. Not making any accusations; just wondering.

  5. Thank you very much for sharing your insight on this paper.

    I am wondering: you state: The mean overjet of the treatment and control groups at T1 was 3.4mm. At the end of T2, it was 2.2mm for the treatment and 2.0 for the control. At T3, the overjet for the treatment group was 2.1mm.

    I believe it should read: At the end of T2, it was 2.2 for the treatment group and 4.7 for the control, not 2.0?

  6. A long way to go before we can even contemplate using this modality on a practical,fee for service ,model. Just not cost effective ,in many areas ,at present

  7. Greetings Doctor!

    Many studies on the eruption guidance appliance still show crowded arches…
    What about transverse arch development…?
    And the more pressing question of taking the orthodontist out of the picture…??

  8. Wondering what are the neurological aspects of reducing afferent information to CNS , killing neurplasticity and altering neuromodulation…besides ortho correction, does anybody here question swallow disorders and some sort of mental retarding?

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