May 20, 2024

Do plastic aligners cause harm?

You might be wondering about the topic of my post. Recently, I read an interesting blog post about a new research paper that proposes a connection between microplastics and nanoplastics (MNPs) and cardiovascular health issues. This made me think about whether plastic clear aligners could contribute to this problem.

Let’s start by looking at the original paper and the blog post.  Several Facebook posts pointed out the blog post on the excellent Ground Truths blog site. 

This is my interpretation of the paper. A team based in Italy did the study. The New England Journal of Medicine published the paper.

Microplastics and Nanoplastics in Atheromas and Cardiovascular Events

R. Marfella et al

New England Journal of Medicine 2024;390:900-10. DOI: 10.1056/NEJMoa2309822

What did they ask?

Their literature review pointed out that MNPs may be a new risk factor for cardiovascular disease.

As a result, they did this study to find out if.

“We can detect MNPs in atherosclerotic plaque and whether this is associated with cardiovascular disease”.

What did they do?

The team did a prospective, multicentre, observational study.  They did this in several stages.

  • They obtained a sample of patients who had asymptomatic carotid artery stenosis who required intervention.
  • The patients underwent carotid endarterectomy.
  • They were then followed for a mean period of 33.7 +/- 6.9 months to monitor the incidence of nonfatal myocardial infarction, nonfatal stroke and death from any cause.
  • Then they analysed the specimens of the atheromatous plaque for MNPs. This allowed them to divide the patients into those with and without MNPs in the plaque.
  • They conducted the relevant exploratory and multiple regression analyses in the final stage.
What did they find?
  • They enrolled 257 patients, with a mean follow-up of 33.7 (+/-6.9 months). Of these, 150 had detectable amounts of MNPs in their plaque.
  • When they looked at their primary endpoints of nonfatal myocardial infarction, non fatal stroke, or death.  They found that these occurred in 8 of the 107 patients (7.5%) without MNPs. This endpoint occurred in 30 of the 150 (20%) group with MNPs.
  • Importantly, patients with MNPs in plaque had a higher risk of having the primary endpoint than those without MNPs. The hazard ratio was 4.53 (95% CI 2.0-10.27). This means that 4.53 as many patients in the MNP group experienced an event compared to the control group.

The teams’ final conclusion was.

“Patients in whom MNPs were detected within the atheroma were at a higher risk of a composite of myocardial infarction, stroke or death from any cause at 34 months of follow up than those in whom MNPs were not detected”.

What did I think?

Importantly, one of the World’s highest-ranking journals published this paper, so we must consider it groundbreaking. The scientific method was sound and very well written and constructed. 

The authors discussed several shortcomings, including possible sample contamination and lack of socio-economic data on the sample, which is an important confounder.

They also mentioned that their results only show association, not causality.

My overall feeling is that this study revealed concerning findings.

What’s this got to do with orthodontics?

You might wonder why I’m bringing this up, but it’s important to note that this is another reason we need to decrease our reliance on plastic materials, including clear aligners, if only for the future health of our children and their children.

Interestingly, this has previously been covered in this excellent narrative review in 2023 and this paper in Orthodontic update.  This drew attention to several interesting facts that I interpreted here.

Although it is widely accepted that aligners release MNPs (micro- and nanoplastics), whether these particles impact our health is unknown. No studies have specifically examined the presence of nanoplastics in patients undergoing aligner treatment or wearing plastic retainers. As such, there is an urgent need for research in this area to assess potential risks and ensure patient safety.

Furthermore, nanoplastics may influence the environment of the oceans, marine life, perhaps climate change, and our overall health. In the words of a clear aligner company, KOL, “You can’t do that with braces.”

Wouldn’t it be great to have an orthodontic appliance made of a relatively inert material that enables us to produce consistent, good treatment results?

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Have your say!

  1. Appropriate and noble in intent, “Money doesn’t care who owns it.”

  2. Fair comments. On the same train of thought, what about composite fillings, which is about 20% plastic. Would you not have concern about the micro-leakage of microplastic from composite fillings which is in your mouth for almost your whole life as opposed to 2-3 years of aligner treatment?
    So, are we going to vilify all dentist that use composite fillings (which is most likely every dentist)?
    It saddens me that our profession has come to insulting one another instead of having an intellectual conversation about different topics within our field.

    • I’m not sure that I vilified or insulted anyone in my blog post. If you think that I have can you be specific and I shall make an edit.

      • Agreed. I found nothing insulting or degrading in the piece.

      • Dr O’brien,
        I am sorry, I did not mean to imply that this particular post has insulted or vilified anyone. It was a general comment on social media posts and previous blogs and sometimes comments that are made on blogs. I find that a lot of times there is a shift from the topic and more an attack on the individual(s) that use a certain product, technique, method. Anyway, that was more an aside comment.
        The real question is about composite fillings and in fact any other material we use in dentistry (previously it was amalgams). In fact, you can broaden this question to anything and in any field. There will always be inherit risks or undesired effect to anything we do.
        Since we are on the topic of environment. Look at electric vs combustion engine vehicles. Electric vehicles still require to be charged on a grid that is mostly coal based. Mining for lithium is not environmental friendly (there is a lot of carbon emission per ton of lithium mined). So, there is always a cost-benefit analysis to anything we do.
        That being said going back to aligner treatment, maybe what you are really saying is if aligners do not work as efficient and effective as braces and there is also a potential health risk then why use them? Then I agree, you shouldn’t use them.
        What if aligners are effective and efficient? Would you still be against using them. Take into account that our patients have composite fillings, they drink bottle water, and our water system is filled with microplastics. I am saying all this because our overall health is not hinged upon aligner treatment and the microleakage from it per se… which I am sure you would agree.
        Which only leads us back to the question is aligner treatment effective and efficient?

        • Hi and no problem, it is easy for confusion to occur in blog comments. I think that you make good points. Yes, you are correct in what I am trying to say. I feel that we should be reducing our reliance on plastic and taking more care of our environment and risks due to plastic. As a result, the risk/benefit balance is important. Currently, there is so little research on the effectiveness of aligner treatment that we do not really know the potential benefits. Neither do we know much about the risk. However, if we also consider that most aligner treatment is done for purely cosmetic reasons we do have to consider whether the risk to the patient and environment is justified. This is exactly why we need to carry out some urgent research. I suppose that this is what I was trying to say in post and I guess that I need to do a follow up? Again thanks for your thoughtful comments

  3. An interesting study, especially in these days. However, I would be far more concerned about the billions of tons of plastic floating around in the Pacific which gets broken down into micro plastics. The damage it is causing to marine life and ultimately us is so far unknown!

  4. No, I do think the points you raised are both valid and pertinent.

    The colleague’s reasoning is quite understandable though, in that amalgam fillings have been all but banished in favor of composite fillings, also without thoroughly considering the possible health effects thereof in the long term. I distinctly remember the palpable unease in the general public when the health effects associated with the long-time mercury leakage from (very stable and long-lived) amalgam restorations suddenly became a hot topic. In the rush to have these stigmatized and ugly fillings removed, the possible health effects resulting from leakage of unpolymerized resin components, inhalation and/or swallowing of nanocomposite particulate and their much shorter survival rate were happily disregarded both by patients and the dental profession. It is quite questionable whether the removal of these amalgam fillings did any favors to the environment, let alone the introduction of composite as a replacement material.

    However, many of the aforementioned points seem to reappear (albeit in slightly different form) in the current craze surrounding aligners. Are the materials used in commercially available or office-made aligners stable enough to prevent the leakage of softeners in the patient’s mouth? Especially in view of their full-time wear combined with regular exchange? I believe it was Eliades who pointed out that aligners present unique risks in that the attachments used are continuously engaged (grated) by the insertion and removal of the aligners, increasing the risk of particulate inhalation and swallowing. Directly printed aligners represent an even bigger challenge in this regard, in that their correct manipulation (curing, rinsing) is paramount in ensuring the mitigation of possible health risks of the (shape memory) materials. And there can be no debate about the significant burden to the environment associated with printing huge numbers of disposable models to vacuum-form, or gallons of alcohol to rinse them.

    So, no. I do not think the points raised vilify anybody. These issues should be thoroughly thought through, if history is to stop needlesly repeating itself.

  5. Do we further extend this topic further to vacuum-formed retainers and their long-term wear? And do we have to include this as another risk of treatment, yet?

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