Anti-wrinkle injections into the masseter, the thick chewing muscle at the angle of the jaw, relax it so that it clenches and grinds less. People have the treatment for night-time teeth grinding (bruxism), jaw clenching, tension headaches and jaw-joint pain, and for a slimmer, softer lower face when the muscle has become enlarged. Relief from clenching usually lasts three to four months; the slimming effect builds over two to three months and lasts longer.
What is the masseter and why treat it?
The masseter runs from the cheekbone down to the angle of the jaw. You can feel it bulge if you put your fingers on your jaw and clench your teeth. It is one of the strongest muscles in the body for its size, and in people who grind or clench, often during sleep and often without knowing, it becomes overworked and enlarged.
That causes two kinds of problem. The first is physical: worn or cracked teeth, a sore jaw in the morning, headaches at the temples, and pain or clicking in the jaw joint in front of the ear (the temporomandibular joint, or TMJ). The second is cosmetic: an enlarged masseter makes the lower face look square or heavy, which some people dislike.
Relaxing the muscle with a botulinum toxin injection reduces both. The muscle can still work, but it cannot clench with full force, so grinding does less damage and the muscle gradually loses some of its bulk.
How does the treatment work?
The practitioner asks you to clench so they can feel the muscle, then injects the medicine into the thickest part of it at two to four points on each side. Treatment takes about ten minutes. The dose is higher than for facial lines, typically 20 to 50 units per side depending on muscle size, which is why it costs more.
Masseter treatment is an “off-label” use of the medicine. The product licence covers frown lines and a number of medical conditions, not the masseter, but prescribing off-label is lawful and routine in the UK when a prescriber judges it appropriate. It does mean that the prescriber’s assessment matters more than usual: they should examine your jaw, ask about your symptoms and explain that the evidence, while supportive, is not as extensive as for the licensed uses.
What does it do for teeth grinding?
For most people the morning jaw ache and tension headaches ease within one to two weeks and stay away for three to four months. Many people find they still grind but with much less force, so teeth are protected and the muscles do not ache. Dentists who see worn teeth often suggest the treatment alongside a night guard rather than instead of one.
It does not treat the cause of grinding, which is usually stress, sleep problems or a bite issue. If grinding is severe or your dentist has found significant wear, see the dentist first; a bite assessment may change what treatment is right.
What does it do for jaw shape?
If the width of your lower face comes mainly from muscle, you will see the jawline soften and narrow over two to three months as the muscle shrinks from disuse. The change is gradual and natural-looking rather than sudden. Two or three treatments spaced four months apart usually give the best result, after which many people need treatment only once or twice a year to maintain it.
If the width comes from bone, the treatment will help with clenching but will do little for shape. A good practitioner will feel the muscle while you clench and relax and tell you plainly which it is.
How long does it last?
- Relief from clenching and pain: three to four months, after which the muscle gradually regains strength.
- Slimming: builds over two to three months and often lasts six months or more, because bulk returns slowly.
- With repeated treatment: many people find the gaps stretch out over the first year.
Our guide to how long anti-wrinkle injections last covers what affects duration in general.
What are the side effects?
Common and temporary: a tired jaw when chewing tough food for a week or two, mild bruising, and tenderness at the injection points.
Less common: a change in the shape of your smile if a small amount of medicine affects the smile muscles nearby, which wears off over several weeks; a feeling that the cheeks look hollow or saggy, more likely in older people or those with little facial fat; and asymmetry if one side responds more than the other, which is corrected at review.
Rare: difficulty chewing or swallowing, which should be reported to the clinic and to NHS 111 straight away.
Because the muscle is large and the dose is higher, this treatment should be given only by an experienced practitioner. Ask how many masseter treatments they do; it is a fair question.
How much does it cost?
Masseter treatment is priced separately from the standard facial areas. Published UK prices commonly start between £250 and £400 for both sides, higher in central London. We do not yet hold enough clinic prices for this specific treatment to publish a typical figure; the cost guide has prices by city for the standard areas.
Check that a quoted price covers both sides and includes a two-week review. Men and people with very enlarged muscles may need a higher dose, and some clinics charge for this.
Who should not have it?
The usual rules apply: not during pregnancy or breastfeeding, not if you have a neuromuscular condition such as myasthenia gravis, and not if you have had an allergic reaction to botulinum toxin before. Tell the prescriber about any jaw surgery, dental work planned in the next month, and any medicines you take, especially muscle relaxants and some antibiotics.
Aftercare
Avoid rubbing the jaw, lying face down, hard exercise, alcohol and heat for the first 24 hours, as with any anti-wrinkle treatment. Eat soft food for a few days if chewing feels tired, and avoid chewing gum for a week. Our aftercare guide has the full list.
Finding a practitioner
Masseter treatment is offered by many of the clinics listed on this site, though it is not always listed as a separate service on their websites. When you contact a clinic, ask whether they treat the masseter, how often, and who prescribes. Look for a doctor, dentist, nurse prescriber or pharmacist prescriber, or a practitioner working under one, and check their registration; our guide to who can give anti-wrinkle injections in the UK explains how.
Sources
- NHS: Teeth grinding (bruxism)
- NHS: Botulinum toxin injections
- Electronic Medicines Compendium: summaries of product characteristics for UK-licensed botulinum toxin type A products, medicines.org.uk
- General Medical Council: prescribing unlicensed medicines (off-label use)