July 13, 2020

Are Clear Aligner attachments invisible or conspicuous?

We all know that the aesthetics of clear aligners are good, and this explains much of their popularity. However, is their appearance affected by the addition of attachments? This new paper looks at this question.

As I have mentioned several times, I am not a Clear Aligner orthodontist, and I have never used this technology. However, since its introduction, I have found it very interesting.  I remember seeing the first Invisalign appliances at trade exhibitions. I also remember seeing a patient with attachments for the first time and spending ages looking at their teeth, trying to work out what the white “blobs” on their teeth were doing. Since then, the use of attachments has become more refined. However, there is no doubt that the attachments influence the appearance of the appliance. In fact, I have seen some people with so many attachments that I have wondered why they don’t just have ceramic bracket treatment. I was, therefore, very interested to see this new paper that the AJO-DDO published.

A team from St Louis did this research.

Esthetic perception of clear aligner therapy attachments using eye-tracking technology

Jessica Kimberly Thai et al

AJO-DO advance access:  https://doi.org/10.1016/j.ajodo.2019.09.014

What did they ask?

They did this study to ask this question:

“Are there any differences in how clear aligner therapy attachments and aesthetic brackets are viewed using eye-tracking”?

What did they do?

They did a rather complex study that had several main stages.

Firstly, they prepared four extra-oral images of teeth and appliances. The photos were of:

  • Clear aligner control with minimal attachments
  • Clear aligner with anterior and posterior attachments
  • Ceramic fixed appliance and 0.016 Ni-Ti wire
  • Clear aligner with posterior attachments.

250 adults selected from approaches at St Louis University viewed the images. They measured their eye-tracking with eye-tracking software.

The 250 participants also completed a short survey on the appearance of the photographs and their aesthetic preferences.

They calculated the following eye movements

  • The viewing pattern of the subjects
  • Their fixation on the images

Finally, they calculated the viewing pattern, the total fixation duration and the overall visit count for the different areas of interest.

What did they find?

They prepared a very detailed review of their findings. I do not have the space to go through all their interesting results in this post. Nevertheless, I think that the most relevant results were:

  • When they looked at the order of fixation. The first image was the aligner control with minimal attachments, then the ceramic brackets followed by anterior and posterior attachments and finally the posterior attachments.
  • The data on the total fixation time showed that they spent the least amount of time fixated on the control (0.73 seconds). Then the images of the ceramic brackets (0.8 seconds), posterior attachments and anterior/posterior attachments (0.81 seconds).  It is essential to point out that they did not state if they detected any statistically significant difference between these times.
  • When they analysed the questionnaire data, they found that the participants selected the minimal attachment control as their preferred treatment option (mean score 1.77 out of 4.0), followed by ceramic brackets (2.18), then posterior attachments (2.58) and finally anterior and posterior attachments (3.47).  This was identical to the ordering of total fixation time and added some validity.
  • They also found that 42% of the participants ranked the minimal attachments, and 44% ranked the ceramic brackets as their treatment of choice.

Their overall conclusion was:

“There is a general desire for clear aligners with minimal attachments and ceramic appliances over clear aligners with multiple attachments”.

What did I think?

This was an interesting study that aimed to answer a complex and clinically relevant question. I also thought that it was great that a research team carried out some research that was relevant to our patients using sophisticated technology.

They presented a large amount of data evaluating the effect of variables including age and ethnicity on fixation times. Unfortunately, I found this somewhat confusing, and I am concerned that I may have missed something in the paper. For example, I am reasonably sure that while they detected some differences in the outcomes that they measured, none of these was statistically significant. As a result, I feel that we can only consider that the findings were weak trends. This is important because this influences the strengths of their conclusions. This was reflected in the authors somewhat cautious conclusions.

Clinical relevance

I have thought about the clinical implications that we can take from this paper. I cannot help feeling that once an operator starts adding multiple anterior attachments to a clear aligner treatment, then they may as well use ceramic fixed appliances, as the appearance is pretty similar. Or am I being too simplistic?

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