An occasionally irregular blog about orthodontics

Removable orthodontic appliances are only worn 9 hours a day!

By on February 4, 2015 in Clinical Research, Recent posts with 15 Comments
Removable orthodontic appliances are only worn 9 hours a day!

Ticking away the moments that make up a dull day…removable orthodontic appliances are only used 9 hours a day!

It’s been a while since I managed to put a Pink Floyd link into a blog post and I know that this one is tenuous, but I have just bought a vinyl record player and got out my old records. One of these was a first day of issue “Dark side of the moon” which include the classic track “Time”..   This would be very valuable, if I had not played it many many times on an old record player. Anyway enough of reminiscing to the mid 1970s and onto this weeks blog.

One of the most difficult questions for orthodontists who use removable and functional appliances is “how do we monitor appliance wear’?  This has been solved to a degree by the development of timing devices. This new paper in the EJO reports on a study that used electronic timers to measure removable and functional appliance wear in a sample of patients.  It is by a team from Tubignen, Germany.

Katharina SchäferBjörn LudwigHannes Meyer-GutknechtTimm Cornelius Schott
Eur J Orthod (2015) 37 (1)73-80 
DOI: First published online: 3 July 2014 (8 pages)


The aim of this study was to measure the hours of wear of removable orthodontic appliances within a sample of German children. They also evaluated the association between duration of wear and gender, age etc.

What did they do?

They recruited 141 patients who were being treated with functional or active removable appliances. Importantly, 136 of these patients were treated in private practices.  This meant that the study had good generalisability because the patients were treated in a “real world” setting and not a university hospital.

Each appliance was fitted with a Theramon Sensor. This measures the ambient temperature and records the time that the appliance is in the mouth.

Each patient was asked by the orthodontists to wear their removable appliance for a minumum of 15 hours.

What did they find?

timing dataThey presented the data in some really nice graphics for each patient.  An example of these are in this screen shot.

I felt that it was really interesting that they found that only 7.8% of the patients managed to wear their removable orthodontic appliance for the prescribed time.  Surprisingly, the mean time of wear was 9.7 hours.  The girls wore their appliance more than the boys and wear time decreased with increasing age.

What did I think?

This was a good study that provided clinically useful information.  While I appreciate that  most of our patients do not wear their appliances for the length of time that we hope.  I was surprised that the wearing time was so low. These results also makes me wonder that if the treatment was working with this low amount of wear time “how long is it necessary for a patient to wear an appliance”?

I was interested that they asked their patients to wear their appliances for only 15 hours. It was not clear to me whether they asked the patients to wear the appliance while they were asleep.  I, and many other orthodontists, ask their patients to wear their appliances for 24 hours a day. So it is a little difficult to extrapolate these findings to my patients. As the 9 hours wear that they recorded may have only been while the patients were asleep?

I would really like to see this study extended to investigate whether the amount of tooth movement was related to the time of wear. This would provide us with great clinical information that would be very useful. I look forward to seeing this.

Because this blog has become more popular than I had every hoped I have had to do some maintenance to increase security and I have upgraded the blog email list management software. This is the first time that I have published a post with it, so I am sorry if there is a little bit of chaos with blog publicising etc. If there is, this will be a “one off”.

ResearchBlogging.orgSchafer, K., Ludwig, B., Meyer-Gutknecht, H., & Schott, T. (2014). Quantifying patient adherence during active orthodontic treatment with removable appliances using microelectronic wear-time documentation The European Journal of Orthodontics, 37 (1), 73-80 DOI: 10.1093/ejo/cju012

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  1. Stephane Reinhardt says:

    Thank you Dr O’Brien for another interesting blog.
    Were the patient aware that they had a sensor on their appliance? If not, it would be interesting to see the difference in the wear time of patient where they would wear it at first without knowing the sensor is there and then after a determined period of time they would be informed of the presence of the sensor. A bit like the Hawthorne effect.
    Also, is there a correlation with wear time and the treating orthodontist? It would be interesting to see if some have better results with their patient than other. I feel that compliance is sometimes related with the connection we have with our patients.
    Interesting also would be to have the orthodontist opinion before the treatment begins on what will be the compliance of each of his patient will be to see if it correlates with the results. Maybe some of us would hit “The wall”…

    • Kevin O'Brien says:

      Thanks and I wondered about this when I read the paper, but I could not find anything about whether the patients knew that they were being monitored. Like you, I would think that this would have an effect. But the data suggests that this was not the case because of the variation in time of wear etc. I am convinced that the way the orthodontist presents and discusses the appliance has an effect. I always remember one of my clinical supervisors, insisted that we all must believe the appliance would work and he almost encouraged us to have a group hug! I try to follow this philosophy without the hug. Nice Pink Floyd reference, I will try to add one to this post but I am comfortably numb and pleased to have so many good comments on this post

  2. I like so much your blog and I have founded many things very useful. Please continue publishing, it’s a pleasure to read you.

  3. Chris Kettler says:

    Like you I ask patients to wear removable appliances, including twin blocks, 24 hours a day. Every now and then the appliance works very quickly. This prompts the question: What are all the other patients doing?

    • Kevin O'Brien says:

      Thanks Chris, yes I sometimes wonder this, but then I have come across patients who I know have only worn their Twin Block for 8 hours a day and their teeth are moving really well. I know that the wear time was not good because they were children of my friends. I think that individual response may have a greater effect than wear time?

  4. Jeet Parekh says:

    Dear Professor O’brien
    Thank you again on your informative blog. Here at the Royal London we are currently undertaking a prospective randomised clinical trial to study the dental and skeletal effects of the twin block appliance on a part time and full time basis. As part of our study we are also using the theramon sensor to objectively measure compliance in each of these groups. It is a little early to provide any results but we look forward to sharing the study in due course.
    Jeet Parekh
    StR Orthodontics

    • Kevin O'Brien says:

      Hi Jeet, this sounds a really interesting study and it will provide us with great clinical information. When will it be completed? Best wishes: Kevin

  5. Shamique ismail says:

    Interesting concept of using the Theramon device to record time of wear or removable appliances.
    I am aware of a paper from 2011 (Ackerman & Thornton) that undertook a ‘pilot study’, with less than 10 pts in a test group, where patients were devised in advance that the amount of wear was being monitored, compared with a ‘control group’ that were not advised. This resulted in 4 hours more wear in the test group…food for thought in terms of what instructions we tell our patients when fitting removable appliances for them.

  6. Jayaram Mailankody says:

    That was a good point made by Stephane and Shamique. In shops and offices like banks, it is customary to find a notice informing ‘The premises are under CCTV survillene’, to ward off temptations to do things one wouldn’t like to be seen dong!
    With modern youngsters, the ‘liberty’ of removal of the appliance becomes a ‘license’ and forgetting to wear the appliance is rampant. To get compliance with retainer wear, I usually tell patients(jokingly) that the appliance is fitted with a micro chip with GPS and timer, and I will get beep, if they keep it off (for longer durations), so better wear them 24 hours!

  7. Katharina Schaefer and Timm Schott says:

    Dear Professor O’Brien!

    Thank you very much for sharing a blog post on our study. We are eagerly following your blog and were very happy to see it published.

    Let us answer some of the questions that are mentioned in your article.
    In our study all the patients were asked to wear their appliances for 15 hours a day. This is a common wear-time for removable appliances in Germany, requiring the patient to wear the device for half the day and while he/she is asleep. The question of “when were the 9 hours wear-time we found?” would indeed be interesting to investigate. What we can say from our results so far, is that most patients wear their appliances during the night with some of them also wearing for a few hours during the day. We haven’t seen patients that are wearing exclusively during the day.

    All patients were aware of the wear-time monitoring. Also, written consent of the parent guardian was present, when the device was inserted. It would surely be interesting to see whether there is a significant difference in wear-time between patients aware and patients unaware of the monitoring process and whether it can contribute to compliance. The results of previous studies according to this question were to the contrary and the studies were carried out with relatively small patient cohorts (Ackerman et al. (2011), Kawala et al. (2013), Pauls et al. (2013))

    One of our findings was that among all the parameters examined (gender, age, type of appliance, insurance status, treatment location), the location of treatment had the most significant influence on wear-behaviour. So we conclude that the relationship between orthodontist and patient may have a major influence on wear-time and Stephane is absolutely right about his feeling.
    In future it would be very interesting to investigate the correlation between wear-time and dental and/or skeletal response. The Theramon Sensor is a great device that might allow us to provide answers to these interesting and important clinical questions.

    Kind regards,
    Katharina and Timm

    • Jayaram Mailankody says:

      Katharina and Timm,
      Let me compliment you for the interesting study as well as revealing significant findings. In the light of your conclusions and evidence thereof, it appears that it would probably be a better practice(in Germany) to instruct the patients to wear the appliance for 24 hours/a day, to get an effective wear of 15 hours/a day. Thus one can ‘compensate’ for the ‘transmission loss’ in the process of ‘instruction and compliance’.
      In fact, we generally advise patients for 24 hrs wear, so that marginal laxity(dilution) in compliance does not greatly effect the outcome.

    • Kevin O'Brien says:

      Thanks for your helpful comments they are really useful. Are you planning to publish anything on whether the results of treatment were associated with the time of wear?
      Best wishes: Kevin

    • Dear Katharina and Timm,
      Thank you very much for your answers to the different questions. I am happy that my feeling was right. One thing I wonder, is if the average wear time would still be the same within different groups where we would give different recommendations (for example 1 group would be asked to wear the appliance 8 hours/day, another one 15 hours/day and a third one 24 hours/day). Could we conclude that wearing time is half of what we recommend or that wearing time would maybe still be 9 hours, regardless of what the recommandations would be. I have a feeling it would be half of the recommandations. But this would be interesting to document especially with the growing popularity of treatments with removable clear aligners (ex. Invisalign). Thanks to both of you for a very interesting study.

  8. Dawn Brown says:

    Very interesting blog. I really enjoy reading these. Small snippets to get you thinking.

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