Botulinum toxin for the masseter

What is Botulinum toxin for the masseter?

The masseter is the strongest chewing muscle and sits at the side of the lower jaw. In treatment with botulinum toxin, a small quantity of the medicine is injected into this muscle. There it temporarily inhibits signal transmission from nerve to muscle, so that tension in the muscle decreases for several months.

Who is it suitable for?

• night-time grinding and clenching of the teeth (bruxism)
• a feeling of tension or pressure in the jaw and temple area
• a pronounced chewing muscle with a markedly square jawline
• alongside dental splint therapy

Benefits

• short outpatient treatment without incision or general anaesthetic
• the effect is time-limited and therefore reversible
• no downtime worth noting
• the dose can be adjusted at follow-up treatments

How it works

1. medical consultation covering symptoms, previous illnesses and medication
2. palpating the tensed chewing muscle and marking the injection points
3. disinfection of the skin over the muscle
4. injection at several points per side using a very fine needle
5. brief period of observation and discussion of aftercare

How many sessions?

1 session per treatment cycle, once per cycle, with a review after about 2 weeks. a top-up is generally required every 4–6 months.

After the treatment

• do not massage or rub the treated area for 24 hours
• do not lie flat for about 4 hours after treatment
• avoid intensive exercise, sauna and solarium on the day of treatment
• avoid very hard or chewy foods for the first few days
• seek medical advice if you have difficulty chewing or swallowing

When are results visible?

Decreasing tension is often noticed after 1–2 weeks — the full effect can usually be assessed after 4–6 weeks.

Possible risks and side effects

• temporary weakness when chewing, particularly with hard foods
• asymmetry caused by an uneven effect on the two sides
• headache in the first few days after treatment
• pain, redness or bruising at the injection sites
• unintended effect on neighbouring muscles, altering the smile or corner of the mouth
• unwanted change to the facial contour, such as a narrower-looking jawline
• reduction of muscle volume (atrophy) with repeated cycles
• the effect wears off after 4–6 months and the symptoms can return
• rarely, allergic reactions to components of the preparation
• with repeated use the effect can diminish through antibody formation

Off-label use: what that actually means

Botulinum toxin is a prescription-only medicine. In Germany it is approved for certain indications, which do not include treatment of the chewing muscle either for bruxism or for aesthetic reasons. Treatment of the masseter muscle is therefore an off-label use — outside the terms of the medicine’s authorisation.

This is legally permissible, but it has consequences you should know about before deciding. The duty to inform is extended: you must be told separately, and verifiably, about the authorisation status, the available evidence and the alternatives. Statutory health insurers do not generally cover the cost. And the medical responsibility for the indication weighs more heavily than for an approved use. For this reason what comes first is always a detailed conversation and written consent, not an appointment for the injection.

How relaxing the chewing muscle works

In grinding and clenching, the chewing muscle works against resistance over long periods, often at night and without the person noticing. The result can be a permanently raised muscle tone, felt as pressure or tension in the jaw, pain in front of the ear, tension in the temples or stiffness in the morning. Over time the heavily used muscle can also gain volume, making the jawline appear broader.

Botulinum toxin blocks the release of the messenger substance acetylcholine at the junction between nerve fibre and muscle cell. Without this signal, the part of the muscle in the treated area contracts less strongly. The activity of the muscle is reduced, not abolished entirely; how strongly depends on the dose. Maximum force decreases. Night-time clenching can decrease in intensity as a result.

The effect is inherently time-limited. The body forms new connections at the blocked nerve endings, so muscle activity gradually returns. After roughly 4–6 months the effect has usually worn off. Anyone seeking sustained relief has to repeat the treatment — or decide together with the treating doctor to stop, and accept that the symptoms may return.

Why dental assessment should come first

Bruxism is not an isolated muscle problem. It can be connected with misalignment of the teeth, with disorders of the jaw joint, with sleep disturbance including sleep-related breathing disorders, with stress, or with certain medications. Jaw and facial pain can also have causes that have nothing to do with the chewing muscle, such as dental disease or problems of the jaw joint itself.

An injection into the chewing muscle addresses none of these causes. At most it can reduce a symptom. A dental or orthodontic examination therefore belongs before the decision, as does the question of splint therapy, physiotherapy and stress management. This page gives general information and replaces neither an examination nor a diagnosis.

What this treatment cannot do

It does not treat the cause of the grinding. Where stress, a sleep disorder or a bite misalignment underlies it, those factors remain. Damage already done to the teeth — worn chewing surfaces, cracks in the enamel, damage to fillings or crowns — is not reversed by it; repairing that is a matter for dentistry. A bite splint, which mechanically protects the tooth substance, is not replaced.

The limits also need naming where facial contour is concerned. A narrower jawline can only result to the extent that the width genuinely comes from the chewing muscle. Where the contour is determined by bone structure, by fatty tissue or by the condition of the skin, treating the muscle changes nothing. Whether there is a muscular component at all in an individual case can only be clarified by examination — and in some cases the result of that examination is that the treatment should be advised against.

The method is not suitable in cases including disorders of neuromuscular transmission, hypersensitivity to components of the preparation, inflammation in the injection area, and during pregnancy and breastfeeding.