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. https://kevinobrienorthoblog.com/cochrane-systematic-review-class-ii-treatment/.  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.

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.