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Dr Tim Pearce
Crooked smiles are quite common – sometimes it is just part of a person’s natural appearance, but they can also be caused by incorrect placement during a botulinum toxin treatment. Both types of ‘crooked’ or asymmetrical smile presentation can be managed similarly.
In this blog, Dr Tim Pearce explains how to correct a crooked smile with botulinum toxin, exploring the anatomy involved in treating this area and the best injection techniques to avoid complications.
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What are the causes of an asymmetrical smile?
When approaching a crooked smile, it is vital, first and foremost, to understand the anatomy causing the asymmetry, reminds Dr Tim. Crooked smiles are very complicated because they represent an asymmetry of the entire lower face.
The patient may have a crooked smile because their cheekbones are not the same on each side, and the muscle attachments pull differently. They may have a much fuller, more volumised fat pad on one side meaning the muscle is resisted in its action. Dental work may also be affecting their smile.
Dr Tim warns that with such diverse options, you should avoid jumping straight into treating the muscles of the lower face just because someone has asymmetry without considering the whole, complicated 3D structure of the lower face.
You must carry out a proper assessment of the patient, and for that, you need to know the anatomy that helps us to smile.
Why is the depressor labii muscle so often affected by botulinum toxin treatments?
This happens because the anatomy is intertwined with two of the muscles we treat on purpose with botulinum toxin; the first, medially, is the mentalis.
The mentalis passes underneath the depressor labii muscle, if you are superficial to the muscle, or if you are too superior when treating, you will overlap with the depressor labii muscle. The result means the patient will no longer be able to pull their lower lip outwards and away from their teeth creating an asymmetry on that side.
The second area is during the treatment of the DAO muscle. This muscle pulls down the corner of the mouth making it a target for treatment which aims to relax a portion of it to achieve a little more upward pull through the muscles that normally pull the cheek upwards.
When treating the DAO, you are very close to the depressor labii muscle that runs underneath; they have a strong overlap. However, the least amount of overlap occurs on the lateral border and intermediately between the oral commissure and the angle of the jaw.
Dr Tim’s preferred injection technique to avoid a problem is halfway between the modiolus and the angle of the jaw, on the lateral border, because it is the furthest place away from the depressor labii.
Diagnosing which muscles are causing an asymmetrical smile
When a patient presents with an asymmetrical smile (after recent treatment), the first thing to do is compare their presentation with all the muscles on the face and assess which muscles are out of balance.
If you have treated the DAO on one side more than the other and caused an asymmetry, the patient may smile differently. It will not appear the same as the more common side effect of treating the depressor labii by accident because the depressor labii pulls the more medial part of the lip down and out; whereas, the DAO operates more laterally with the oral commissure being pulled downwards (as in the illustration).
Asymmetry can be caused by other botulinum toxin treatments elsewhere in the face. For example, if you treat too deeply in the upper face, you may affect zygomaticus major meaning the patient cannot pull the muscles upwards to create a smile on one side.
Similarly, with treatments for masseter reduction, we commonly see risorius affected.
If this happens on both sides of the face, it will not be an asymmetrical presentation, but the patient will be unable to smile widely. If it only affects one side, it can be very striking and upsetting for the patient when one side of their face smiles and the other does not.
Safe injection techniques are your key to avoiding such complications, reminds Dr Tim. Learn how to avoid mistakes when injecting masseter muscles with Botox and avoid this Botox injection pattern when treating the masseter.
How to manage a patient who has developed an asymmetrical smile following botulinum toxin treatment
The first thing is to acknowledge that even minor asymmetry can be distressing for patients, especially when it affects their smile, as others may frequently ask about it – “What’s wrong with your lip?” – which can lead to emotional distress. It can make a person very miserable when they cannot smile properly, particularly with more obvious risorius muscle complications, thus empathy is crucial, notes Dr Tim.
Before addressing the problem, you must take time to truly understand their experience and listen. Once they have expressed their emotions and feel heard, it is easier to explain the anatomy and context for the complication, making them more receptive to any solutions.
Patients often appreciate learning about their anatomy and what has caused the issue, so explaining that a small amount of misplaced botulinum toxin can be corrected or asymmetry decreased with a similar treatment helps them make an informed decision, reducing emotional stress by assuring them it is a temporary issue.
What treatment options are available if you have caused an asymmetry by affecting the depressor labii muscle?
The decision to correct asymmetry should be based on weighing up between a more balanced appearance and another potential side effect; you are not going to be able to restore them to normal, only time will do that.
If the depressor labii muscle is affected, achieving symmetry may result in a smaller, less open smile. In Dr Tim’s experience, most patients tend to choose symmetry over a larger smile, but it is important to explain that while symmetry can be restored, their smile will look different for a few months. Being upfront about these options helps patients decide, and they are usually content when they know what to expect.
Watch the video for Dr Tim’s injection technique for treating the depressor anguli oris while avoiding risorius and the depressor labii muscles.
Remember, if you have any questions or topics for discussion, you can find Dr Tim Pearce on Instagram.
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Aesthetics Mastery Show
How to fix an asymmetrical smile with BOTOX
Dr Tim says:
“In this episode I discuss how to fix a crooked smile with Botox, the anatomy involved with treating this area and the best techniques to avoid complications. “
Watch the full Aesthetics Mastery Show here.
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BOTOX (Botulinum Toxin) eLearning Courses
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In addition, browse our FREE downloadable resources on complications.
Botox® is a registered trademark of Allergan Aesthetics plc.
Dr Tim Pearce eLearning
Dr Tim Pearce MBChB BSc (Hons) MRCGP founded his eLearning concept in 2016 in order to provide readily accessible BOTOX® and dermal filler online courses for fellow Medical Aesthetics practitioners. His objective was to raise standards within the industry – a principle which remains just as relevant today.
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