May 1, 2023

lower face anatomy

Treating the masseter muscles with Botox® (botulinum toxin) is often used to address bruxism or teeth grinding but can also be used aesthetically to slim the jawline by reducing the dominating effects of an overactive masseter muscle.

In this blog, Dr Tim Pearce warns against searching the Internet for ‘Botox patterns for masseter reduction’, and explains why this could result in an upsetting side effect for your patient.

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Potential side effect when treating the masseter muscle

When treating the masseter muscle with Botox, if you place your needle and dose of botulinum toxin a little bit superior or a little bit medial to the muscle, you can affect the risorius muscle. This can cause an upsetting asymmetry for the patient when they smile because you have relaxed the small muscle that pulls the corner of the mouth when we create a broad smile.

The risorius is commonly known as the smiling muscle and is defined by Germann and Al Khalili in the Anatomy, Head and Neck, Risorius Muscle,

“The risorius muscle is a narrow bundle of muscle fibres that becomes narrower from its origin at the fascia of the lateral cheek over the parotid gland and superficial masseter and platysma muscles, to its insertion onto the skin of the angle of the mouth. There is a risorius muscle located on either side of the lips in most individuals…

The risorius muscle’s function is to aid in facial expression by pulling the corner of the mouth laterally via its contraction in an outward and upward motion. In conjunction with other facial muscles, this helps to create a smile or a frown, and myriad other expressions in-between.”

How to avoid impacting risorius when injecting the masseter

Avoid-Masseter-Botox-PatternOne of the issues noted by Dr Tim stems from searching the Internet, or Google® using phrases like, ‘masseter reduction Botox pattern’ or ‘masseter injection points for botulinum toxin’. This search results in a common answer that he believes is somewhat fallacious and inaccurate and could cause the known side effect if followed.

In these illustrations, a line is often drawn to the oral commissure. Looking at the top, right hand side of that line and then inferior to it is very close to the insertion point of risorius. Dr Tim notes that when teaching other aesthetic clinicians and watching them in practice trying to implement such a pattern, it may only be 0.5-1cm of difference, but it can place them inadvertently into risorius and risk affecting the smile. For this reason, he does not like this ‘line’ as a guide and instead favours another.

Dr Tim chooses instead to line up with the mental crease. This means you are treating the lower third of the masseter muscle, and the boundary is the mental crease which takes you away from the insertion point of risorius and reduces the risk of smile impact.

As well as using a different boundary line, Dr Tim notes that another important factor is to ensure that your placement is deep enough. The risorius muscle is inserted into the fascia around the masseter, making it relatively superficial, hence depth is another consideration. Dr Tim advises that you can effectively avoid the risk of impacting the smile when performing a masseter reduction treatment with Botox by being both inferior to risorius and deep enough that you avoid hitting it.

Read more on this topic from Dr Tim in know your muscle anatomy to avoid side effects from Botox in the lower face and how to avoid mistakes when injecting masseter muscles with Botox.

If you have any further questions about Botox treatments, Dr Tim would love to hear them, you can find Dr Tim Pearce on Instagram.

Botox® is a registered trademark of Allergan Aesthetics plc.

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Aesthetics Mastery Show

Avoid this Masseter Botox Pattern

In this episode, Dr Tim looks further at issues surrounding the masseter and how to avoid nasty side-effects from using inappropriate injection patterns. Watch the full Aesthetics Mastery Show here.

The show has had thousands of views and over 20 comments from practitioners and patients, including:

Practitioner @kubraneslihankurtoktay7928 said:

“That’s why i always use long needle for masseter injection. Thank you for these great informations ! From now on, i will drive a line to the mental crease instead of oral commissure!”

Client @bodyjewels asked:

“I would so very much love your advice, I have this done at every three months. Each time they do it different, and I end up with jowl flab.. Driving me crazy. I need cogs almost to pull the skin back. I am about to DIY it myself.”

Another patient @yummieyummy asked:

“Hi is it normal that my injector only injected into only one spot on my muscle, rather than multiple spots? (30 units dysport each side)”

To which @drtimpearce replied in person”

“Probably not the average treatment, but it could be right for you- were you happy with the result?”

BOTOX (Botulinum Toxin) eLearning Courses

If you want to increase your confidence or learning how to handle complications, Dr Tim Pearce offers two comprehensive courses that are highly rated by our delegates:

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In addition, browse our FREE downloadable resources on complications.

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.

Our exclusive video-led courses are designed to build confidence, knowledge and technique at every stage, working from foundation level to advanced treatments and management of complications.

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