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Masseter Injections: Jaw Slimming, Teeth Grinding and the Things Clinics Leave Out
What masseter injections can change, what they cannot, how to tell whether a wide jaw is muscle or bone, and what to expect over the following months.
Masseter injections use botulinum toxin, often called masseter Botox, to relax the masseter, the large chewing muscle at the angle of the jaw. When an enlarged muscle is relaxed, it gradually becomes smaller over the following weeks. The lower face looks slimmer and less square, and the force of teeth clenching and grinding is reduced. Treatment takes about 10 to 15 minutes. The change begins after about two weeks, is clearer by about a month, and lasts around four to six months.
It is one of the most effective non-surgical treatments for the shape of the lower face, and one of the most useful for people who grind their teeth. It only works when the width comes from muscle, though, and repeated heavy treatment in the wrong face can leave the lower face looking hollow. This guide explains how to know whether it suits you.
What masseter injections are — and what they cannot do
The masseter is the muscle that closes the jaw when you chew and clench. In some people it is naturally large; in others it enlarges from habitual clenching or grinding, often during sleep. A large masseter makes the angle of the jaw look wide and square and can make the lower face look heavy or masculine.
Relaxing the muscle with small doses of botulinum toxin reduces its activity. Like any muscle that is used less, it shrinks over the following weeks. The jaw angle becomes softer and narrower, and the face takes on a more oval or tapered shape. At the same time, the clenching force on the teeth and the jaw joint is reduced.
It only slims a jaw that is wide because of muscle. If the width comes from bone, fat, jowls or the salivary gland in front of the ear, injections will not help (see The most important thing on this page).
It does not treat the cause of teeth grinding. Stress, sleep and bite problems may still need a dentist's assessment or a night guard.
It is temporary, and it needs repeating to maintain the effect.
The most important thing on this page: muscle, bone, fat or skin?
A wide or square lower face can have several causes. Only one of them responds to masseter injections.
Muscle. Place your fingertips just in front of the angle of your jaw and clench your teeth. If a firm bulge pushes out under your fingers, much of the width is muscle. This is the situation masseter injections treat.
Bone. Some jaws are wide because the bone flares outwards at the angle. Relaxing the muscle makes little difference.
Fat or fullness in the lower cheek.
Jowls. Soft tissue that has descended along the jawline with age. A facelift is the treatment.
Salivary gland. An enlarged salivary gland in front of the ear can mimic a wide jaw. It needs medical assessment.
The second rule is caution with older or thinner faces. In younger people with a strong muscle and firm skin, slimming the masseter gives a clean, tapered result. In older people, or those with thin faces and loosening skin, repeated high doses can leave the lower face looking hollow or make jowls look heavier. Doses and intervals should be tailored, and sometimes the right answer is not to treat.
Why people consider it
A wide, square lower face from a large jaw muscle.
A softer, more oval or tapered face shape.
Teeth grinding or clenching (bruxism), often at night.
Jaw pain, tension headaches or jaw joint strain related to clenching.
Tooth wear or cracked teeth from grinding.
Teeth grinding and jaw pain
Masseter injections reduce the strength of clenching and grinding, which can ease jaw pain, tension headaches and pressure on the teeth. Many people notice they wake with less jaw tension. They are best used alongside a dental assessment, because a night guard may still be needed to protect the teeth, and grinding can be linked to bite problems, stress or sleep conditions that need attention in their own right.
Who this suits
Masseter injections suit adults whose lower face is wide because of an enlarged masseter, or who grind or clench their teeth. The most common group is women between 30 and 55 who want a softer, slimmer lower face, but men and younger adults with a strong muscle are also good candidates.
It is not suitable during pregnancy or breastfeeding, with neuromuscular disorders such as myasthenia gravis, with infection at the injection site, or with a known allergy to the product. See anti-wrinkle injections for more on botulinum toxin, its products and safety.
Tell your practitioner about any previous jaw treatments, dental problems, jaw joint problems, and any blood-thinning medicines or supplements.
The treatment
The jaw is examined at rest and while clenching, to map the muscle. The skin is cleaned, and numbing cream may be applied. The medicine is injected into several points of the lower, thicker part of the muscle, avoiding the areas close to the smile muscles. Treatment takes about 10 to 15 minutes, and you can return to normal activities immediately.
Dr. Feryal Yıldız takes a preventive approach to masseter Botox, carefully tailoring the injection technique to minimize the risk of jowling before it occurs.
Rather than simply reducing masseter volume, her technique focuses on preserving lower-face support, maintaining a defined jawline, and preventing unwanted laxity while achieving a refined, natural-looking result.
After treatment
- Keep your head upright for the first four hours.
- Do not rub or massage the jaw for the rest of the day.
- Avoid heavy exercise for the first 24 hours.
- Avoid saunas, steam rooms and hamams for the first day or two.
- Chewing may feel slightly weaker for a few weeks, especially with tough or chewy foods. This is expected.
When you will see results, and how long they last
First 1–2 weeks. The muscle relaxes, and clenching force reduces.
From about 2 weeks. The jaw begins to look slimmer.
About 1 month. The change is clearer.
Around 2–3 months. The fullest slimming effect, as the muscle continues to reduce in size.
4–6 months. The effect gradually fades as the muscle recovers.
With regular treatment, many people find the muscle stays smaller and treatments can be spaced further apart.
Masseter injections or jaw surgery?
Masseter injections slim a jaw that is wide because of muscle. They are quick, with no downtime, but temporary, and they need repeating.
Jaw reduction surgery reshapes the bone at the angle of the jaw. It is permanent, and it suits jaws that are wide because of bone. It is a major operation with a longer recovery and specific risks, including injury to nerves.
The right choice depends on whether the width is muscle or bone, which is assessed at examination.
[TO CONFIRM — whether Dr Yıldız performs jaw contouring surgery or refers]
Side effects and risks
Serious complications are uncommon when an experienced doctor uses licensed products. The recognised side effects and risks include:
Temporary chewing weakness or tiredness, particularly with tough foods.
Bruising, tenderness or a small bump at the injection points. These are short-lived.
Headache. It is mild and short-lived.
An uneven smile, if the medicine affects nearby smile muscles. It is temporary, and careful placement avoids it.
A bulge when clenching, if part of the muscle is not treated. It is usually corrected at review.
Asymmetry, usually correctable at review.
Hollowing of the lower face or heavier-looking jowls, in older or thinner faces, especially with repeated high doses.
Allergic reaction. It is rare.
If you are travelling to Istanbul
Most international patients have masseter injections during a trip for another treatment. Because the slimming effect develops over weeks, you will see the result at home, not before you leave. Ask for a written record of the product, the dose and the injection points, so that whoever treats you next can repeat or adjust the treatment.
Choosing a practitioner
Choose a doctor. Botulinum toxin is a prescription medicine. Ask who will inject you and what their qualification is.
Expect an examination of your jaw at rest and while clenching, to confirm that the width is muscle.
Ask which product will be used, and see the sealed packaging.
Ask whether masseter injections suit your age and face shape, and how often treatment should be repeated.
Be wary of very low prices, treatment without examination, and non-medical settings.
Frequently asked questions
What does masseter Botox do?
It relaxes the masseter, the large chewing muscle at the angle of the jaw. The muscle gradually shrinks, slimming the lower face, and clenching and grinding are reduced.
How long until I see results?
The jaw begins to look slimmer from about two weeks, the change is clearer at about a month, and the fullest effect appears at around two to three months.
How long does it last?
Around four to six months. With regular treatment, many people find the effect lasts longer between sessions.
Will it help my teeth grinding?
It reduces the force of clenching and grinding, which can ease jaw pain and protect the teeth. A dental assessment and night guard may still be needed.
Will it make my face look hollow?
In a face that is wide because of muscle, it gives a natural slimming. In older or thinner faces, repeated high doses can cause hollowing, so doses should be tailored.
Will I be able to chew normally?
Yes. Chewing may feel slightly weaker with tough foods for a few weeks.
Does it hurt?
Most people feel a brief pinch. Numbing cream can be used.
Can it slim a jaw that is wide because of bone?
No. A jaw that is wide because of bone needs a different approach, such as jaw contouring surgery.
Is it safe?
Serious complications are uncommon when licensed products are used by an experienced doctor. Temporary chewing weakness or an uneven smile can occur.
Can it be combined with other treatments?
Yes. It is often combined with anti-wrinkle injections elsewhere on the face, and sometimes with volume treatment to balance the face.
Arranging a consultation
If you are considering masseter injections, the useful next step is an examination of your jaw at rest and while clenching. That should come with an honest answer to whether the width is muscle, bone or something else, and a plan that suits your age and face shape.
You are welcome to contact the clinic to arrange a consultation with Op. Dr. Feryal Yıldız. There is no obligation to proceed, and you should not be asked to decide on the day.
