May 08, 2023

Which functional appliance do children prefer?

There has been a large amount of research into the effectiveness of functional appliances. Most of this has looked at the morphological effects of treatment and provided us with valuable clinical information. 

Recently, researchers have started moving their focus away from this aspect of treatment using endless analysis of cephalometric tables towards measuring outcomes relevant to patients. These outcomes are important because it allows us to consider patient preference when planning treatment. This new paper provides helpful information from a randomised controlled trial.

This paper is open access, so everyone can read it without charge or needing to be a member of a specialist society.

What did they ask?

“What are childrens’ experiences with fixed and removable functional appliances?”

What did they do?

This was a qualitative study nested in a randomised controlled trial. The PICO was:


Children aged 10-14 years with Class II Division 1 malocclusion with an overjet greater than 7mm.


Hanks Herbst appliance


Twin block appliance


Participants perceptions of their appliances and treatment.

One specialist orthodontist did all the treatment. They asked the patients who were having TB treatment to wear the appliance full time apart from when eating and playing contact sports.

If participants could not wear their Twin Block, they were offered treatment with the Herbst appliance.

The team did face-to-face qualitative interviews with a sample of the participants. Then, they repeated the interviews until the themes and responses started to repeat. This is called the saturation point.

The interviews were recorded and transcribed. Finally, they analysed the interviews with Framework analysis. This identified the main themes and perceptions of the participants.

What did they find?

Eighteen participants agreed to take part in the study. They reached data saturation at the 14th participant.

I can’t provide information on all the results as the team reported a large amount of data. In addition, they included many interesting and relevant direct quotations from the interviews. 

I thought that these were the most important points:

  • First, both groups of participants mentioned functional problems and symptoms.
  • The Herbst group most frequently mentioned mastication problems.
  • The TB group were concerned with speech problems.
  • Other symptoms were reported equally by the groups. These included discomfort that disrupted their daily lives.
  • It also appeared they adapted to overcome problems. This depended on their ability rather than the appliance.
  • Notably, the TB group could remove their appliance in social situations.
  • Their peer group significantly influenced their perceptions of the appliance, particularly their appearance and functional concerns.
  • Breakages were more of a problem for the Herbst group.
  • Finally, in all groups, if they had to start treatment again, they would choose the Herbst. 
What did I think?

This was an important, highly clinically relevant piece of research. It provided a great deal of information that we can use to fully inform our patients about their treatment. So, I would certainly, include their main points to advise and consent my functional appliance patients.

The main strengths of this study are that it is an RCT. The two appliances are very different, and the team reported outcomes relevant to our patients and clinical practice.

Final comments

I want to quote their conclusions as the important take-home message for this landmark study. I cannot summarise this any better.

“This study explains how fixed (HH) and removable (MTB) functional appliances can negatively affect a child’s QOL and behaviours.

MTB was viewed as the suitable option for children with self-discipline and an active lifestyle; however, HH was preferred by the majority for the convenience of requiring less management and dependence on self-discipline.

Children also wished to be given greater autonomy, with appliance choices and involvement in decision making”.

Anyone interested in functional appliance treatment should read this important paper.

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Have your say!

  1. It’s time Kevin tell the UK Public about Myofunctional influences on airway and health

  2. Please consider making a donation to Dr. O’Brien’s blog. He does an awesome job reviewing and critiquing important research.

    Best wishes to all,

    Dan Rinchuse

  3. It’s an interesting study but the criteria “If participants could not wear their Twin Block, they were offered treatment with the Herbst appliance” adds bias to the outcome, at least to some extent. In any case, the bigger question is “What is a functional appliance?” In my understanding it’s an historical misnomer and is, by and large, a mandibular advancement device used in children (not dissimilar from mandibular advancement devices used for OSA in adults).

  4. I only do TB in age 7-9
    and what about Invisalign with MA?

  5. I think that the big question would be is there any appliance “older” patients really enjoy? Also, would the sagittal discrepancies have been more effectively treated at an earlier age? QOL must be measured at not just the moment in time but over a broad range.

  6. The Herbst has been referred to as an “invisible headgear,” and the TB is no different. Has Newton’s third law been overturned by our reality-bending governments? This study seems to ask, “By which means would you prefer to have your maxillary dentition retracted, reducing your tongue space (which can adversely affect your airway), and distalizing your mandible (which can lead to pain and dysfunction)?” The patient’s preferences and experiences seem to be the last thing we should care about.

  7. The main strengths of this study are that it is an RCT.


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