Botox is a great way to get rid of some of those pesky wrinkles on your face, but did you know that it’s also effective for masseter muscle hypertrophy?

The masseter muscle is the one that gives you the ability to chew and grind your teeth. It sits in the back of your jaw and connects to the temporalis muscle (which sits on top of your cheekbone) and the lateral pterygoid muscles (which are located on either side of your jaw).

When this muscle becomes enlarged, it can cause issues with chewing, talking, and swallowing. In some cases, it will also cause migraines or TMJ disorders. The reason why this happens is because overuse of the jaw leads to inflammation and edema in those muscles. This can result in scar tissue formation within them which causes them to grow larger than normal—which then leads to more pain during chewing or even when just speaking!

Botox works by blocking nerve impulses from reaching these muscles so that they cannot contract as much when they are signaled by nerves throughout your body. When this happens less often during everyday activities like eating or talking, then there will be less pain associated with those activities as well!

TREATMENT TIPS

A 42-year-old female patient presented to our office seeking cosmetic treatment because she wasn’t happy with the appearance of her face. Upon examination, I noted that her face was very squared in the lower jaw, which can lead to a more masculine appearance and fuller face. Physical examination revealed that she had a very thick masseter muscle.

The patient confirmed a history of teeth grinding and waking up with daily migraine headaches. She reported that she had sought medical treatment from several doctors and dentists for the headaches and grinding and had gone through three different mouth guards and took a prescription medication for migraines, but nothing helped. The masseter muscle tends to be thick in patients who grind their teeth or clench tightly at night either because of nervousness or out of habit. With prolonged grinding and clenching, that muscle gets thicker and thicker over the years, which leads to a wider jaw.

I suggested treatment with injection of onabotulinumtoxinA (Botox) in her masseter muscle to relax the muscle so she would not be able to clench, grind, or bite down as hard. This relaxation in the muscle would lead to thinning of the muscle, which would result in thinning her face and alleviating her teeth grinding and headaches.

Figures 1a-b. Patient before (top) and one month after (bottom) injection of 100 units of Botox into the masseter.

The patient agreed to the treatment. I injected 100 units of Botox (See Figures 1a and 1b).

The patient returned for follow up one month later saying, “This has changed my life. I don’t take any of my migraine medicines any more, I don’t need my mouth guard any more, my face is thinner.”

Botox injection into the masseter muscle is ideal for patients who are grinding, clenching, and wearing out their teeth and need a lot of dental work, for patients who have frequent tension or migraine headaches, and for patients who do not like the shape of their face because of square or thick jaw line and who want to appear more feminine.

The amount of Botox needed to treat this area ranges between 60 and 100 units of Botox, depending on the thickness of the muscle. Patients can expect headaches and clenching to go away within a week and will see the full effects of jaw thinning about one month after treatment, when the muscle has had time to atrophy.

In 10 years of performing this treatment, I’ve never had one side effect other than some bruising, which is a potential side effect whenever you inject into the face. There’s no swelling, no downtime. It is the most magical treatment I’ve ever done. Patients can go back to their normal activities. They can exercise. They can do whatever they want that day. Most people come in during their lunch break, they get injected. You can’t even see the pinprick of the needle.

Patients should be counseled to return to the office for treatment every six months, which is longer than the typical two-month interval for injecting Botox in other areas. Most of my patients present back in six months and say they were just starting to get headaches again or were just noticing that it was time for treatment and with follow-up injection; they feel great again. I’ve never had a patient who wanted me to re-treat in less time because I inject a high enough dose. Under-dosing the muscle in efforts to get by with a smaller dose or because a patient wants to spend less money will definitely lead to the patient coming back sooner for follow-up treatment, and s/he won’t see the ideal effect for headaches.

When injecting into the masseter, it’s important to feel where the masseter muscle starts and ends. The masseter muscle is like a triangle, so I actually go into each vertex of the triangle and test it for the masseter. It’s also essential to know where the risorious muscle is, which holds the corner of the mouth out when you smile. It’s important to not hit the risorious muscle or that side will not move, resulting in a crooked smile.

For optimal results, be sure to use a high enough dose—if you under-dose, treatment will not be effective. It’s not like other injection areas where you can say, “OK, we’ll just inject 10 units and see what it looks like.” It doesn’t work the same way—you have to use a higher dose to ensure optimal results.

What causes unilateral masseter hypertrophy?

Treatment of the case above with Botox®:

• Improved chewing
• Diminished pain
• Prevented  jaw from disengaging or clicking
• Improved facial contour

through a sequence of three injections to the left masseter (25 units in 1 cc of onabotulinumtoxinA = Botox ®/Botox Cosmetic® (Allergan, Inc) with EMG guidance.  Initial treatment resulted in 3 months of benefit with the second injection more durable but still warranting a third injection one year after the second.

Masseter muscle enlargement (hypertrophy) can be accompanied by pain and is often erroneously ascribed to a disorder of the adjacent parotid gland. An excellent review by Fedorowicz et al (2013) identified potential causes to be 

• emotional stress
• chronic bruxism 
• masseteric hyper-function
• microtrauma

​In some cases the masseter enlargement is thought to arise from a disorder other than work hypertrophy with the absence of a certain type of muscle fiber supporting a cause other than ‘work hypertrophy’ 

• ​clenbuterol (a bronchodilator with growth-promoting properties prohibited in animal husbandry and sport, used to treat reactive airway disease Thevis 2013) induced hypertrophy
• overuse of anabolic steroids
• localised scleroderma
• facial hemi-atrophy (see: (under construction) Hemifacial Atrophy (Parry-Romberg Syndrome PRS) Romberg Syndrome atrophy in trigeminal nerve distribution )
• multifactorial origin in combination with a genetic basis
• benign masseter hypertrophy is also compatible with a rare genetic condition known as hypertrophic branchial myopathy 

Recommendations for evaluation have included

• Computed tomographic (CT) scan, magnetic resonance imaging  (MRI) scan, or both (considered the gold standard in confirming a clinical suspicion).
• Ultrasonographic measurement.
• Muscle biopsy.
• Morphometric analysis
• Electromyographic measurement.

Reported treatments include:

• Use of muscle relaxants
• Bite adjustments or involve the use of splints on the teeth.
• Surgical reduction of the jaw muscle
• Injections of botulinum toxin type A directly into the muscle are other treatment options.
  • The 2013 Cochrane analysis (Fedorowicz 2013) concludes: “Although the use of botulinum toxin injections might appear to have certain advantages over surgery the authors of this review did not find any high quality studies that evaluated the effectiveness and potential side effects of botulinum toxin type A for the management of benign masseter hypertrophy. Well-designed randomised controlled trials are needed to assess the effectiveness and safety (i.e. side effects) of this intervention.”

Botulinum Neurotoxin Treatment (BoNT)

Although the largest reported experiences with use of BoNT come from the cosmetic use for facial recontouring, it has been used successfully to treat masseter hypertrophy to address pain associated with unilateral enlargement.

A review (Yeh 2018) addressing publications from January 1994 to Feb 2018 emphasized analysis of complications – that overall were considered rare with the majority appearing with in 2-4 weeks of the injection and disappearing within 12 weeks. 

How Many Botox Units Do I Need?

Although it’s often seen as a cosmetic-only treatment, Botox is actually a medical procedure. Like all medical procedures, the recommended dosage depends on many factors. What works for one patient may not work for another.

Luckily, the question “How many Botox units do I need?” isn’t something you typically need to worry about—your medical provider will prescribe your correct dosage. By speaking frankly with your provider about the results you’re looking for, you can work together to determine exactly how many Botox units you’ll need.

With that said, because Botox is often priced per unit, it can be helpful to know roughly how many units of Botox your visit will require. To that end, we’ve put together these guidelines on the typical recommended Botox unit requirements for popular treatments.

How Botox is Measured

Before we can fully explain how many Botox units you’ll need for any procedure, it’s important to discuss what a Botox unit is.

The active ingredient in Botox is called botulinum toxin type A. It’s a well-understood toxin that is completely safe and effective when injected in small, controlled doses. Don’t let the term “toxin” scare you; Botox has been used in the medical field for decades to treat facial spasms, reduce skin wrinkles, help with TMJ (pain or discomfort in the jaw joint) and more.

However, because the crucial ingredient in Botox is a toxin, controlling the amount used in any given injection is essential. To ensure a high degree of accuracy, professionals use the term “unit of Botox” to refer to the amount of botulinum toxin type A present. One unit of Botox corresponds to a specific amount of the active ingredient—not the total amount of liquid in a vial.

Sometimes, you may read somewhere or see that Botox treatments are measured in “syringes.” Take these guidelines with a grain of salt; Botox can come in vials of 50 or 100 units, so using “syringes” as a measurement isn’t as accurate as using units.

Finally, keep in mind that Botox is a brand name. Several other neuromodulators use the same biotechnology, such as Dysport and Xeomin. These options rely on the same active ingredient, but they can be more or less potent than Botox. As such, the number of units you’ll need may differ. Today, we’re focusing specifically on Botox units.

An Area-by-Area Guide to Botox Units

Now that you understand what a unit of Botox is, it’s time to look at how many units you may need. Once again, keep in mind that these guidelines are rough estimations based on the average number of units used for each treatment area. Depending on several factors (which we’ll touch upon shortly), your requirements may vary.

Here’s the amount of Botox you might expect your provider to recommend for the following treatments:

• Forehead lines – The long, horizontal lines that can crease your forehead typically take 8 to 20 units.
• Frown (glabellar) lines – Known as the “11” lines that can appear between your eyebrows usually require 20 to 30 units.
• Eyebrow lift – When using Botox to bring about a slight lift in the eyebrows, you’ll generally need 2 to 5 units per side.
• Crow’s feet – These small wrinkles in the corners of your eyes can be smoothed out with about 9 to 14 units per side.
• Bunny (nasalis) lines – The tiny lines that show up on the bridge of your nose when you smile or wrinkle your nose can be treated with 4 to 10 units.
• Masseters (jaw slimming) – Your masseter muscles sit between the ear and mouth and can contribute to jaw pain and discomfort. Treating this area (whether for TMJ relief or facial contouring) requires anywhere from 15 to 50 units per side.
• Lip lines (perioral lines) – known as “smoker lines” 4 units.
• Lip Flip – 4 units
• DAO – These vertical lines are located between the corners of the mouth and chin. They can cause a downturned mouth – 2-6 units per side.
• Mentalis (Dimpled chin) – Reducing the dimples that appear across your chin is possible; all it takes is 4 to 15 units of Botox.
• Neck (platysmal) bands – Vertical necklines or “bands” that can appear on the neck over time. With 20 to 40 units, you can soften the appearance of these bands while giving your neck a more youthful look.
• Underarms – Aside from its cosmetic uses, Botox is also indicated as a treatment for excessive sweating (hyperhidrosis). This treatment calls for 100 units.

Factors That Can Affect the Number of Botox Units You Need

As you may have noticed, there’s a substantial gap between the lower and upper limits for many of the above treatments. That’s because every patient is different; it’s hard to know how many Botox units you’ll need until you book a consultation with a medical provider.

Depending on the factors below, your treatment requirements may be at the bottom, middle or top of these ranges—or even beyond them. However, note that the Botox label specifies that the cumulative dose should not exceed 360 total units administered over a three-month span.

Muscle Size and Strength

The most important factor for gauging the required amount of Botox units is muscle size and strength. After all, Botox works by blocking the signals from your nerves that cause your muscles to contract. If the targeted muscles are larger or stronger than average, you may need more units to convince those facial muscles to relax. On the flip side, weaker muscles may require fewer units overall.

Muscle size and strength can differ from person to person for several reasons. Some are due to genetics; others are based on day-to-day habits. For instance, something as simple as regularly chewing gum could cause your masseter muscles to become bigger and stronger. Other facial muscles that are affected by ordinary movements, include:

• Smiling
• Frowning
• Squinting
• Laughing
• Pursing or puckering the lips

Age

Your age impacts the size and strength of your facial muscles, but it also plays other roles in determining how many Botox units you’ll need.

As we age, our skin naturally becomes thinner, less plump and less smooth due to volume loss. Wrinkles also become more pronounced over time.

With that in mind, if you receive your first Botox treatment at 65, you may need more units to diminish deeper lines than if you were 25. For this reason, more and more patients are starting Botox treatments at a young age.

Sex

As a general rule, men tend to require more Botox units than women for the same treatments. The reason is simple: Genetically, males tend to have bigger and stronger facial muscles than females.

Of course, there are always exceptions, but we tend to use more Botox with our male patients.

Metabolism

Just as your body’s metabolism processes incoming calories, it also processes Botox. As such, if you have a high metabolism, your Botox treatment may not last as long. To combat the effects of a high metabolism on injected Botox, your provider may suggest using additional units to extend the amount of time between treatments.

Desired Results

Finally, your exact Botox requirements will depend on your cosmetic goals. If you want that ultra-smooth look, you’ll generally need more Botox units to achieve it. If you’d rather maintain a complete range of facial movement, you and your provider might opt for a smaller dose.

While you can use this guide as a baseline, the only way to know exactly how many Botox units you’ll need is to speak with a professional. Your provider will listen to your concerns and goals, ask questions about your health history and present you with different options that suit your needs and budget. Through regular consultation—and a follow-up appointment two weeks after your first injections—these dosages may be adjusted to provide even better results.

At Derma Health Skin & Laser, our amazing staff is here to walk you through the Botox injection process from start to finish. All of our injectors and aestheticians go through advanced education and training to ensure you leave feeling satisfied with your outcome and results.