Masseter Reduction: Slimming a Wide Jaw and Easing Clenching

The lower part of your face looks wide or square. Perhaps you also clench or grind your teeth. You wonder whether a masseter injection could change the contour of your jaw or ease that clenching. The masseter is the muscle that closes your jaw when you chew. The injection targets this muscle, but it can also affect nearby muscles. So the first step is to work out whether the masseter is what makes your jaw wide.

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At a glance

Five things to know before deciding

The masseter: the muscle that closes your jaw when you chew; if it gains volume, it can widen the lower face and make it look square. During the assessment, the doctor distinguishes between muscle and bone and assesses how fat and skin contribute to your concern.
What the injection does: it relaxes this muscle, which can slim the contour and reduce the force of clenching; it does not reshape bone and does not target fat. Its effect is temporary, and nearby muscles can also be affected.
Teeth clenching: it can ease the clenching, but it does not cure bruxism; a dental splint from your dentist is another option.
Risk specific to this area: a temporary loss of chewing strength, a change in your smile or a hollowing of the cheek are possible.
Before any treatment: a medical assessment, which can lead to postponing, changing or declining the injection.

The masseter: the muscle that can widen the lower face

The masseter sits on each side of the face, against the ramus of the jaw, the part of the bone that rises toward the ear. When this muscle gains volume, it is called masseter muscle hypertrophy: it changes the lines of the face and can make the jaw look square. This increase in volume can go along with clenching or grinding the teeth, heavy gum chewing, damaged teeth or a painful jaw joint. Its exact cause is unknown. Pain and tooth wear can also accompany this increase in volume.

Resting face of a fictional man, three-quarter view, neutral expression, with a naturally wide, square jaw, with no markings and no exaggeration.

A large muscle is, however, only one of the possible explanations. During the assessment, the doctor seeks to distinguish between muscle and bone; the assessment is also used to assess how fat and skin contribute to your concern.

To tell the muscle from the bone, the examination may include feeling the masseter while you clench your teeth: the muscle then stands out more. A panoramic X-ray can also show whether the bone is more pronounced at the angle of the jaw. If it is a double chin that concerns you, the doctor checks during the assessment what causes the fullness under your chin, rather than assuming it comes from the masseter. Reshaping the jaw contour means changing its outline rather than reducing its width.

The muscle: The masseter gains volume; it stands out more when you clench your teeth, and an injection can act on it.
The bone: The angle of the jaw is itself more pronounced; an injection changes nothing there.
Fat and skin: Their contribution to the appearance of your jaw needs to be assessed; a masseter injection targets the muscle, not fat or skin.

What changes when an injection relaxes the masseter

This injection blocks the message the nerve sends to the muscle. The masseter first loses strength, then its volume decreases. The lower face may then become slimmer, and clenching may become less forceful. The term neuromodulator is also used, with well-known brand names such as Botox^® or Dysport^®. CARE MD offers masseter injection as an aesthetic option.

The injection is mainly considered when the examination shows that the muscle is what widens the jaw. It does not reshape bone and does not target fat. During the assessment, the doctor needs to establish whether targeting the muscle would address your concern. Slimming and relief are not guaranteed, and the result varies from person to person.

It is the same type of injection used to soften the crease between the eyebrows, the frown line: it relaxes a muscle, whereas a filler adds volume. Cosmetic injections are chosen primarily based on what you want to change.

It acts on: The volume and strength of the masseter.
Its limits: It does not reshape the jawbone and does not target fat or skin; nearby muscles can also be affected.
When to postpone or rule out the injection: Inflamed or infected skin, hypersensitivity to an ingredient of the product, neurological disorders, difficulty swallowing or breathing problems, pregnancy.
Who gives it: A physician, or a nurse injector supervised by a physician.

Who it is for

A person whose lower face is widened by the muscle, after an assessment by a physician.

Teeth clenching and bruxism

When you clench or grind your teeth, the masseter is the muscle doing the work. An injection can reduce the force of this clenching and relieve the pain it causes. It does not make the habit of clenching go away: there is no established cure for bruxism, and the injection is not one. The effect of the injection on bruxism itself remains uncertain. For bruxism during sleep, devices and biofeedback may help, with no guarantee of effectiveness.

Your dentist may also suggest other options, which CARE MD does not offer:

If your teeth are showing increasing wear or your jaw joint hurts, see your dentist or your physician first: these problems need to be examined before any cosmetic injection.

The dental splint: Your dentist may suggest this dental splint to protect your teeth; its effect on tooth wear and pain is not guaranteed. It is also among the non-surgical options considered for mild masseter hypertrophy. Favourable results are possible, but the likelihood of success with these treatments alone is not established.
Biofeedback: A therapy that may help with bruxism during sleep, with no guarantee of effectiveness.
Associated factors: Stress, caffeine, alcohol and tobacco are associated with sleep bruxism; this does not mean that changing them will make the clenching go away.

When the effect appears and how long it lasts

The effect is not immediate: the muscle relaxes, then its volume decreases. Changes in the jaw contour take longer to appear than the softening of a wrinkle. The effect is temporary, and several sessions may be needed to maintain it. The result and its duration vary from person to person and are not guaranteed.

The risks specific to this area

You use the masseter to chew. The nearby muscles take part in smiling, and the volume of this area also shapes the hollow of the cheek. An injection can therefore have several effects specific to this area:

This injection requires a qualified health professional who has experience with it. Take the time to understand the risks before deciding.

Chewing strength: A temporary loss is possible; chewing can become harder.
Smile: The smile can be limited or altered when the injection reaches the nearby muscles.
Hollow cheek: Loss of volume below the cheekbone can make the cheek look hollow.
Bulging: The muscle can stand out more in one spot instead of flattening.
Sagging: The skin may look less taut where the muscle has become smaller.
At the injection site: Pain, bruising, sometimes headaches.
Other possible effects: Facial pain, swelling around the eyes, rash or allergic reaction, local muscle weakness; they are usually temporary, but can last several months.

Signs that require medical attention

After the injection, a change in your smile or muscle weakness can get in the way of your daily life. Call CARE MD if your smile becomes asymmetrical, if marked weakness sets in, if a rash or an allergic reaction appears, or if an unusual effect persists or worries you. This call does not replace immediate medical care if you have the following signs. Only a physician can say what is going on.

Before any injection, jaw joint pain or teeth showing increasing wear are reasons to see a dentist or a physician first.

Why a medical assessment comes first

Before offering any treatment, the physician has to determine what is widening your jaw. An assessment of masseter hypertrophy may include a discussion with the physician, feeling the muscle while you clench your teeth and then while you rest with your mouth slightly open, and a panoramic X-ray to distinguish muscle from bone. Prepare your questions about fat, skin, jaw joint pain and your clenching habits. The assessment can lead to postponing, changing or declining the injection, or to referring you to your dentist.

Prepare a list of your medications and your previous procedures in this area. Tell the physician about your medical history and whether you are pregnant or breastfeeding: these can change the decision. Also ask whether this injection can interact with other products, other treatments or the medications you take for other health problems. Prepare your questions about the change you can expect, the risks specific to this area, how long the effect lasts and what happens if you are not satisfied with the effect.

Ask us about the width of your jaw

Frequently asked questions

Does a Botox® injection in the masseter really slim the jaw?

It can slim it when the muscle is what widens the lower face: the masseter loses strength, then volume. It does not reshape bone and does not target fat. Nearby muscles can also be affected. Slimming is not guaranteed and varies from person to person. A medical examination can help determine what is widening your jaw.

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