August 03, 2020

Do aligners cause less pain than fixed appliances?

Here is another paper on clear aligners. This one looks at the patient’s experience of pain and anxiety with clear aligners or fixed appliances.

Some sources have suggested that there are less pain and discomfort with clear aligners than with fixed appliances.  However, a recent study has indicated that any differences are low and are of short duration.  This new study could have added to this useful information.

A team from China did this study. The European Journal of Orthodontic published the paper.

What did they ask?

They did the study to:

“Compare the pain perception, anxiety and Oral Health-Related Quality of Life between patients receiving clear aligners or fixed appliances during the initial stages of fixed appliance treatment”.

What did they do?

They did a prospective cohort study.  This was the PICO

Participants: Orthodontic patients over 18 years old having treatment for both arches.

Intervention: Clear aligner treatment

Comparison: Fixed appliance treatment

Outcome:  Pain perception assessed with visual analogue scales. The secondary outcomes were Oral Health Quality of Life and anxiety.

They enrolled 110 patients in the study.  They matched 55 clear aligner patients with 55 fixed appliance patients. The patients had the same gender, similar ages and treatment complexity (assessed by ICON).

They did a sample size calculation that suggested they needed 19 patients in each group. But they enrolled 55 into each group.

They collected the data on pain, anxiety and oral health quality of life over 14 days. Using visual analogue scores and validated questionnaires.  They also collected data on the patient’s demographics and malocclusion.

What did they find?

At the start of treatment, there was no difference between the groups, apart from the income level.  This was higher in the clear aligner group.

They found that patients who had a fixed appliance reported significantly higher pain and anxiety scores and had a lower oral health quality of life than the clear aligner group. Unfortunately, they presented their data in the form of graphs, and I could not accurately extract the data for this post.  It was also not clear whether these differences were clinically significant.

They concluded:

“Patients treated with clear aligners experienced lower pain levels, less anxiety and higher Oral Health Quality of Life”.

What did I think?

Initially, I thought that it was great to see a paper that looked a patients perceptions of treatment. These are important outcomes and are not confined to cephalometrics etc.  However, I did have some significant concerns with this paper.

I do not usually review papers that are not trials. However, I decided to have a close look at this paper because of the subject area and the conclusions.  Furthermore, I am trying to be constructive in my reviews of articles as I do not want to be more critical. Nevertheless, when a paper that addresses a controversial area has been published by a refereed journal, I think that it is necessary to be critical when there are flaws in the article.  Unfortunately, this is such a paper.


I think that this paper has the following significant problems:

  1. The fixed appliance group had a mean lower income. It, therefore, had considerable selection bias. This is particularly important because income impacts on anxiety, pain perception and quality of life. As a result, the results could be influenced by the significant confounder of income. This was not addressed statistically.
  2. The final sample size was higher than the sample size calculation suggested. This means that the study could be overpowered and small effect sizes could be statistically significant but not clinically different.
  3. The study was done over a very short time, and the findings are very limited.
  4. Importantly, the study was confined to negative experiences only. It is important that these experiences are placed in a wider context. If one appliance is less effective than another, how pivotal is the effect on pain and quality of life? It would be interesting to be able to review these findings in conjunction with data relating to the effectiveness of these appliance systems to provide a more informative comparison.

As a result, I am afraid that I cannot agree with their conclusions.  However, this is up to you to decide.

Other comments

Finally, this is the second paper that I have posted about recently that has substantial flaws and was published by the EJO.  I wonder if the members of the editorial board of the journal would like to comment?

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Have your say!

  1. For those of us with less sharply honed analytical skills, the details provided which clarify your feelings about the publication are both interesting and useful. The EJO reply (or, lack of such) will be interesting, indeed. Additionally, a response from the authors would add to the mix.

  2. Thank you again Dr O’Brien for an always interesting view on articles.
    The problem I have with this article is that patients having fixed appliances can not compare to anything else and it is the same with patients having clear aligners.
    My experience of using braces for 21 years and clear aligners for 16 is that, patients who experienced both methods say that it is much easier with aligners. Nothing scientific: a clinical opinion of my reality. And even in these cases, for most of them, they were treated with fixed appliances more than 20 years ago. They compare to a perception they have from that time. Things have change in 20 years.
    What would be interesting would be a study where patients would have one arch in clear aligners and one arch in fixed appliance. Then they could ask the patients to compare pain and discomfort for each arch.
    Again it would not be perfect because it could depend on the types of mouvements and mechanics in place (attachements or not can have an effect on comfort level) but that would give, in my opinion, a better conclusion.

  3. Interesting topic , I have a question /remark: – the sample size they calaculated as19 was based on what population size ?
    I believe that pain perception varies from person to person regardless of their socio-economic status.
    I would like to make a similar study and your observations will be a great help
    Thank you for this very useful blog

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