October 21, 2019

How stable is eruption guidance appliance treatment?

It would be great if we could intercept the development of malocclusion. Unfortunately,  we do not know much about the effectiveness of interceptive treatment.  This new paper provides us with interesting information on a potentially simple method of intercepting mild Class II malocclusion.

One area of orthodontics that still causes considerable controversy and debate is early interception.  In many ways, this is a perfectly reasonable aim. There is no doubt that if we could achieve this by using a simple appliance, we would be providing an excellent service to our patients.  The debate around this concept has been ongoing for many years.  Unfortunately, the proponents of this approach illustrate their philosophy with case reports and firmly debate its benefits. Meanwhile, others ask for evidence to underpin the philosophy, and the wheel keeps turning. I have posted about this many times before, and currently, the evidence suggests that there are limited benefits obtained from attempts to intercept Class II malocclusion.

However, there has been some exciting research into the use of pre-formed eruption guidance useful or myofunctional appliances. These are appliances that combine the effects of a functional appliance and a positioner. As a result, they may correct overjets and crowding. Importantly, because the appliance is preformed, there is no need to take impressions. This sounds great to me, but does this work?

There have been some trials in this area, and I have posted about them before. In short, they show that the appliances may be effective. However, there are issues with low levels of co-operation.  In my view, this is a major drawback of these systems.

This paper is a follow-up study of a trial. This Norwegian and Finland based team did this study. The Angle orthodontist published the paper, which means that it is open access, and anyone can read it!

Stability of orthodontic treatment outcomes after 1-year treatment with the eruption guidance appliance in the early mixed dentition: A follow-up study

Rita Myrlund, Katri Keski-Nisula, Heidi Kerosuo

Angle Orthod. 2019;89:206–213.  DOI: 10.2319/041018-269.1


This paper was published in March of this year, and I managed to miss it, so I am sorry that I am not entirely up to date.

What did they ask?

They did this study to answer these simple questions:

“What is the stability of any correction of malocclusion in children who had a one year eruption guidance treatment”?

“Does a delay in the start of early Eruption Guidance Appliance treatment affect the outcome of treatment”?

What did they do? 

This was a follow-up study of their previous paper that was published in 2015.  I will outline the main features of this study and the current follow up.  The PICO was:

Participants:  Children in the early mixed dentition with Angle Class I or Class II                         malocclusion with overjets greater than 5mm, deep bite and moderate crowding.

Intervention:  Treatment with an Eruption Guidance Appliance (EGA).

Control:          Delayed treatment with EGA one year later.

Outcome:        Dental measurements and cephalometrics.

This was a randomised controlled trial. They enrolled 159 7-9-year-old children from one municipal town. The children were screened for malocclusion, and then 48 were selected to take part in the study. These children were randomised into treatment (EGA) and control groups. Randomisation was done by drawing lots, and allocation concealment were good. The groups were balanced for age at the start.  The EGA group of patients was treated for 12 months.

When the trial ended, they treated the control group patients for 12 months with the EGA.

The mean ages of the groups in months were 7.7 years (SD=0.5) for the EGA group and 9.1 years (SD=0.6) for the control group. Therefore, this part of the trial was looking into the effects of treating children at different ages with the EGA

They then followed all the participants in both groups until they were 12 years old.

They collected the records at the start of the study (T0), after completion of treatment (T2) and at the final follow up (T3). Study casts were taken at all stages of the study. They took cephalograms at T0 and T2 for both groups. Finally, the participants completed a journal to record their compliance.

Data analysis was done using simple univariate analysis.

What did they find?

At the end of their study, they collected data on 35 participants.  Three had dropped out from the EGA group, and seven of the control group dropped out. This is important because it led to unbalanced groups and a potential loss of power.

I have extracted the most important data from the tables in the paper.

Overjet in mm
Group T0 T1 T2
EGA early 4.9 (1.2) 2.6 (1.3) 3.5 (1.2)
EGA later 5.1 (1.4) 2.6 (1.1) 2.9 (1.2)

They also showed that when crowding was present at the start of treatment from T0 to T2, the mean mandibular width increased from 25.0mm (SD=1.7) to 25.9mm (SD=1.2).

They also made a comparison between ANB values of the study participants and a sample of children from the Norwegian growth study. They divided the data into boys and girls, and this was rather complicated.  In general, any differences were small, and importantly they did not find any statistically significant differences.

Finally, they stated that 31% of the participants reported good compliance, 40% were moderate, and 29% were classified as poor compliers.  The most common reason for dropping out of the study was not being able to wear the appliance.

Their overall conclusions were:

“Early correction of overjets with an Eruption Guidance Appliance is effective, providing the EGA is worn as a retainer. Furthermore, postponing treatment by a year may not influence the treatment outcome”.

What did I think?

This was an interesting and ambitious study. The trial was well done, and I fully appreciate the difficulty of carrying out long term studies into early intervention.  I think that the authors should be commended on this trial.

As with all trials, there are some problems. The most important one for this study was the drop out rate. This is very relevant when we see that there are more dropouts in one arm of the study. This is because this introduces bias.  Furthermore, I was a little concerned that the drop out rate could result in a lack of power and the risk of a false rejection of the null hypothesis.

I was interested to see that the authors felt that the EGA appliances were useful.  This really depends on whether you think that the effect size is clinically significant. For example, if we look at overjet correction for the EGA early group. The pre-treatment overjet was 4.9mm, and this reduced to 3.5mm at the end of the study.  I do not think that this is clinically significant. There were similar small changes in other outcomes.

Final comments

My final feeling is that  I am not sure that this treatment was worth the effort and cost to achieve such small changes early. We also have to consider the poor co-operation rates. As a result, I cannot help feeling that while these appliances may have some potential, we do not see worthwhile clinical changes in any of the trials that have been published.  This type of treatment needs much more research before we can promote it to our patients.

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Have your say!

  1. I really appreciate your blogs and your views. Well done. Andre

  2. Kevin,
    There were 2 things I found interesting about this study. As I read it, Early treatment with this appliance has essentially no benefit, because the effect was no different than not wearing anything. Further more, the study seems to show that wearing the appliance during the later time period resulted in a net increase in OJ! (2.6mm to 2.9mm). I also have trouble how the EGA (early) group could act as control group for the EGA (late) group when the EGA early group was wearing the appliance every other night. It seems that they were comparing every other night wear to full time wear. In this regard, every other night wear actually caused an even larger increase in OJ than the full time wear. Who wants to have their patients wear a class 2 corrector that actually increases OJ??? Am I missing something?

  3. I’ve had great success with night time EG appliances and compliance but the average wear time is more than a year.

  4. As an orthodontist for 30+ yrs, trained at OSU, I’ve used pre-made removable appliances invented by Board certified orthodontist and professor, Earl Bergerson, today called “The Healthy Start system”. Many of these children never required fixed orthodontics. In those days, SDB was not investigated, however, bruxism and snoring stopped per parents comments. Recently, even younger patients ages 2 and up with SDB and more are correcting their swallow patterns and building out better skeletal/dental facial profiles including airway by using a simple questionnaire provided by the healthy start company. Take a serious look! I was an early user of Invisalign (1999) because of my background of early ortho treatment with kids. Many referring drs were skeptical, look where we are now. Kids deserve a break too along with parents seeing their kids struggle in school let alone at night breathing. Dentists have the training and talent and it’s time to get on board.
    Look at my youtube channel and see for yourself…Dr.Anthony Marino, orthodontist.

    • Dear Dr. Marino

      I heard Dr. Bergerson lecture about his success with snoring and restless sleeping toddlers in Boston last month where we had both been invited speakers…..he was brilliant. I am curious sir, when, and why did you pursue diagnosing and treating children in the primary dentition, and did you maybe do your post-graduate orthodontic training at a program that (unusually) had prepared you for managing behavioral issues (i.e., common/intrinsic fears of kids, and their parent(s) often associated with orthodontic Tx and clinical settings per se)?

      I personally think that a crucial omission in the ADA’s CODA-guided curriculum for post-graduate trainees in Orthodontics, and thus, a possible/probable(?) explanation for why others in US (AAO) and other global orthodontic societies’ leaderships’ and memberships’, are so resistant to even considering ‘under age 7′ orthodontic Dx/Tx.

      I’m so curious Dr. Marino about why behavior guidance (BG) training experiences are not part of the US’ CODA-guided curriculum for post-graduate Orthodontic training programs, but is of course, included within the Pediatric Dentistry curriculum, that’s a no-brainer. But this particular CODA curriculum exclusion of BG for Ortho post-grad trainees pretty much implies, and endorses(?), that orthodontists do not need to have didactic and clinical experiences in child BG theory and practice, because they will seldom, if ever, need these skills….the rationale possibly being that children, say ‘under age 7′, would seldom, if ever, benefit from orthodontic/dentofacial orthopedic risk assessment, diagnosis and appropriately/validated therapeutic intervention…..could I be even partially right here Dr. Marino?

      Given myriad published evidence, mostly of observational study design, as were data in support of penicillin’s discovery, infection control in dental offices, hand washing performing autopsies/before delivering babies, scurvy-vitamin C relationship, typhoid and water-borne pathogens(Broad Street pump-UK), Einstein’s relativity theory, etc., etc., etc., in the medical and dental literature spanning from the late 19th-Century (see ref. #’s 22-26 in “Physical Assessment in Pediatric Sleep Hygiene and Airway Health’ https://ancestralhealth.org/wp-content/uploads/2019/08/AHS-Sleep-Disorders-in-Pediatric-Dentistry.pdf) to the present day, that (at least) transverse maxillary deficiency is very often a co-morbid condition with naso-respiratory incompetence and post-adenoidectomy apnea recurrence…..under the age of 7, do you think maybe our efforts to persuade some now resistant orthodontists to re-consider their resistance to earlier intervention, might ‘not’ be such a futile ambition?

  5. Thx for posting Kevin. It highlights what I have pointed out with the Myofunctional studies in that they do something, but the reduction in overjet is small (1.5mm – 3mm at best). The drop out rate also means these are the ‘best of the best’. Although these appliances are cheaper to provide, if a patient knew they had a more effective option but for more cost, what informed choice would they make?

  6. In addition to the small treatment effect the initial OJ was not very high either, almost a normal Oj really.

  7. The authors of the study have to be congratulated for their efforts, it provides us an answer to lot of questions about EGA and myofunctional appliances. I think that the results of the study give us the evidence that we looked for in order to use these appliances in daily practice. The early use of the EGA can be cost effective comparing to traditional braces later even with an OJ of 3.5 mm at the end of retention ( significantly better than 4.9 mm).
    This can be interesting for low income countries also.

    • I think it’s important to note that the overjet figures above are of averages. When dealing with averages over a pool of subjects, you have to look at the statistics and not the simple numerical difference between two values. Being very familiar with these appliances and having seen case after case, overjet is one of the easiest corrections EGAs (Nite-Guide, Occlus-o-Guide, etc.) can correct. These appliances don’t over correct. Severe overjets are washed out by the statistics but are very easily and predictably corrected with this form of treatment, due to the chondylar growth they encourage (as long as growth remains). Please refer to some case examples in this following study and how this study’s results have similar if not a lot of the same conclusions as the one above:
      Dentofacial Changes after Orthodontic Intervention with
      Eruption Guidance Appliance in the Early Mixed Dentition
      Katri Keski-Nisulaa; Leo Keski-Nisulab; Hannu Saloc; Kati Voipiod; Juha Varrelae

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