What is the masseter muscle and how is it linked to teeth clenching?

The masseter is a thick chewing muscle that runs from the lower edge of the cheekbone to the angle and back edge of the lower jaw. You can easily feel it with your hand at the lower back part of your cheek when you clench your teeth. It is one of the main muscles that close the jaw and transmit force to the teeth while chewing.

Clenching your teeth unconsciously during the day or grinding them in your sleep makes this muscle work harder and longer than necessary. Like any muscle, the masseter can thicken when it is constantly loaded. As a result, some people develop a lower face that widens to the sides, with a “square” or angular jawline.

How does teeth clenching affect the mouth and teeth?

Bruxism is not only a cosmetic issue; it has direct dental consequences. Findings we frequently see during examinations include:

• Flattening, wear and shortening of the chewing surfaces and the edges of the front teeth
• Notch-shaped tissue loss at the necks of the teeth and sensitivity to cold and heat
• Cracks and fractures in fillings, crowns or porcelain restorations
• Pain and fatigue in the jaw and temples on waking, and difficulty opening the mouth
• Noises, clicking or pain in the jaw joint (TMJ)
• In people with gum disease, excessive forces increasing the load on the supporting tissues

From a periodontal point of view, the last point is especially important: in teeth with reduced gum and bone support, heavy clenching forces can contribute to tooth mobility becoming noticeable. For this reason, gum health is always assessed in patients with bruxism.

How does masseter Botox work?

Botulinum toxin type A is a medicine that temporarily reduces transmission between the nerve and the muscle. When injected into the masseter, the muscle is not completely paralysed; its contraction strength is reduced. This has two consequences:

1. Functional effect: The force placed on the teeth and the jaw joint during clenching is reduced. Many patients describe relief in morning pain and muscle fatigue.
2. Effect on appearance: A muscle that works less gradually becomes thinner. This slimming does not happen immediately; the literature states that the muscle shrinks gradually over weeks, and that several weeks are needed to see the full effect.

An important point: the masseter is not the only chewing muscle. Other strong muscles, such as the temporalis muscle in the temple, are not affected, so after a well-planned treatment you can still eat and speak. In the first weeks you may feel mild fatigue with hard foods or foods that need prolonged chewing.

Who may it be suitable for?

Masseter Botox is not a standard procedure for everyone; the decision is made after an examination. It is generally considered in the following situations:

• People with clear signs of clenching/grinding on examination whose muscle pain continues despite a night guard
• People bothered by a wide lower face caused by an enlarged muscle, who have realistic expectations
• Patients with extensive cosmetic or implant-supported restorations in whom clenching forces should be reduced (as a supportive measure, based on the doctor’s assessment)

The use of botulinum toxin for bruxism may not be among the official labelled indications of some products; your doctor will inform you about this and obtain your written consent.

Who should not have it?

The main contraindications listed in textbooks and product information are:

• Pregnancy and breastfeeding
• Active infection, acne or skin disease at the injection site
• Myasthenia gravis, ALS and similar neuromuscular diseases
• Known allergy to any of the product’s ingredients
• A bleeding disorder or use of blood thinners (to be assessed together with the doctor)
• Use of certain medicines that can affect nerve-muscle transmission (for example, some antibiotics)
• Unrealistic expectations

Be sure to mention all the medicines you take and any illnesses you have had during your examination.

Night guard or masseter Botox?

These two methods are not competitors; they are often complementary. The table below summarises the differences:

For many patients, the first step is an examination of the teeth, gums and jaw joint, bite (occlusion) adjustment if needed, and a night guard. Masseter Botox is discussed as an additional option for patients whose muscle-related complaints persist despite this approach, or who have cosmetic expectations.

What does the treatment process look like?

1. Examination: Tooth wear, restorations, gum health and the jaw joint are checked; the muscle is examined by hand and its borders are assessed while you clench your teeth.
2. Information and consent: The expected effect, duration and possible side effects are explained.
3. Treatment: A short procedure performed with fine needles. The injection points and amount are determined by the doctor according to your muscle structure.
4. Follow-up: A check-up is usually planned a few weeks later to assess the effect. If you are visiting Istanbul from abroad, let us know your travel dates so we can plan this follow-up with you.

What are the risks and possible side effects?

With proper patient selection and correct technique, serious problems are rare; still, there are things you should know:

• Common and mild: Redness, slight swelling, bruising and tenderness at the injection site
• Temporary chewing fatigue: Especially with hard foods
• Smile asymmetry: Can occur if the product spreads to the neighbouring smile muscles; it is temporary
• Rare: Difficulty speaking or swallowing. If you notice such symptoms, contact your doctor without delay.
• Reduced effect: In a very small number of people, the effect may decrease over time due to the development of antibodies to the product.

Most unwanted effects caused by botulinum toxin resolve on their own as the effect of the product wears off.

Frequently asked questions

Related pages

Medically reviewed by: Dr. Dt. Mehmet Fuat BozabaSpecialist in periodontology · September 2026

If you would like an examination for teeth clenching, jaw pain or worn teeth at our clinic in Bahçelievler, Istanbul, you can message us on WhatsApp or call +90 544 289 66 33.

Sources: Small R, Hoang D. A Practical Guide to Botulinum Toxin Procedures. 1st ed. Lippincott Williams & Wilkins (Wolters Kluwer), 2012. · Kontis TC, Lacombe VG. Cosmetic Injection Techniques: A Text and Video Guide to Neurotoxins and Fillers. 1st ed. Thieme, 2013. · Pirayesh A, Bertossi D, Heydenrych I (eds). Aesthetic Facial Anatomy Essentials for Injections. 1st ed. CRC Press, 2020.

This article is for information only; diagnosis and treatment planning are determined solely by a doctor after an examination.