Teeth clenching (bruxism) and botulinum toxin for the masseter

What is bruxism?

According to international consensus, bruxism is a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth and/or bracing or thrusting of the lower jaw. It can occur during sleep (sleep bruxism) or while awake (awake bruxism)^[1]. Many people do not realise they clench their teeth at night; tiredness or pain in the jaw or temple area in the morning, headaches or wear on the teeth may suggest it.

More than one factor may play a part in bruxism, and these factors differ from person to person. For this reason, the assessment should cover not only the muscle but also the teeth and the jaw joint.

The masseter muscle and botulinum toxin

The masseter sits at the angle of the jaw and is one of the muscles that works hardest during chewing. In people who clench their teeth constantly, this muscle can become more prominent over time. Botulinum toxin temporarily reduces the signal from nerve to muscle in the area where it is applied, so the strength of the muscle's contraction decreases.

A meta-analysis pooling randomised controlled trials reported reductions in maximum bite force and pain intensity in the first months after botulinum toxin treatment compared with placebo; between 3 and 6 months, this difference became smaller^[2]. In other words, the effect is temporary and wears off on its own over time.

How is the treatment done?

• An examination comes first: the jaw muscle is assessed by hand, and your history of teeth clenching and your symptoms are discussed.
• The treatment is given with a fine needle at a few points in the masseter muscle at the angle of the jaw. A topical anaesthetic cream is applied beforehand if needed.
• Male patients are advised to come clean-shaven.
• After the treatment, it is recommended not to wash the area for 1–2 hours and to avoid make-up and massage. You can return to daily life straight away.

The effect begins to be noticeable around day 3 on average and settles by days 7–10. The follow-up takes place within 30 days; no top-up is done after this period. How long the effect lasts varies from person to person.

How it relates to your dentist and a night guard

One of the methods dentists often use for bruxism is a night guard (occlusal splint). A night guard aims to protect the teeth from wear, while botulinum toxin temporarily reduces the strength of the muscle. The two serve different purposes and do not have to replace each other.

In a randomised trial in patients with sleep bruxism and jaw-muscle pain, both the night guard and botulinum toxin improved pain and quality of life at 3 and 6 months; on some measures of jaw movement, the night guard showed a small advantage^[3]. If there is tooth wear, a fracture or a problem with the jaw joint, it is advisable to have an assessment together with your dentist.

Possible side effects

There may be mild pain, redness or bruising at the injection site. Mild discomfort when chewing or a feeling of tiredness in the jaw may be reported; in the randomised trial above, most patients who received botulinum toxin reported mild discomfort while chewing^[3]. A meta-analysis examining the effect of repeated treatments on the jawbone reported a thinning of about 6% in the outer layer of the jawbone in humans, with no marked change in bone volume or density; the authors noted that more studies are needed on long-term effects^[4]. For this reason, the treatment interval and the amount are planned by the doctor.

Treatment is not carried out during pregnancy or breastfeeding. If you take blood thinners, mention this at the examination; do not stop your medication without consulting your doctor.

Further reading

• Botulinum toxin (botox)
• What to keep in mind after botox
• Botox or filler? The difference between the two treatments
• Preparing for an aesthetic treatment