Pain around the temporomandibular joint, or TMJ, can make chewing, speaking and waking in the morning uncomfortable. Some patients also notice tight jaw muscles, aching temples or tenderness after clenching their teeth.
In some cases, overactive chewing muscles such as the masseter and temporalis contribute to this pain. A dentist may consider botulinum toxin type A when muscle-related jaw pain continues despite conservative treatment. The injections reduce the force of muscle contraction for a limited period. Some patients report less pain or tension, and the masseter may also lose some volume as its activity decreases.
Dentists use the term temporomandibular disorders, or TMD, for conditions that affect the TMJ, the chewing muscles or both. Botulinum toxin does not treat every cause of pain in this area. Its potential role mainly concerns patients whose symptoms come from overactive or painful chewing muscles.
Pain around the TMJ can come from several structures. The joint itself may become inflamed or develop problems involving the disc inside it. The masseter, temporalis and other chewing muscles can also become sore or overworked.
Botulinum toxin acts on muscle activity. For that reason, a dentist may consider it when an examination suggests that excessive muscle contraction contributes to the pain.
You may notice symptoms such as:
• aching or tenderness in the masseter muscles
• pain around the temples
• jaw fatigue during chewing
• discomfort associated with clenching
• enlarged or prominent masseter muscles
These symptoms do not confirm that the muscles cause the pain. A dentist needs to examine the jaw and rule out dental disease, joint problems and other possible causes before discussing injections.
Botulinum toxin has a more limited role when pain comes from inflammation inside the TMJ, structural joint changes or disc displacement. Those problems may require a different treatment plan.
Your nerves use acetylcholine to signal a muscle to contract. Botulinum toxin type A reduces the release of acetylcholine at the point where the nerve meets the muscle.
A dentist injects small amounts into selected parts of the masseter, temporalis or another target muscle. The treated muscle then contracts with less force for a period of time.
This reduction in force may lower the load on painful chewing muscles when you clench. Some patients report less tenderness, fatigue or jaw tension after treatment.
The injections do not necessarily stop the behaviour that caused the muscle activity. You may continue to clench your teeth because of stress, sleep-related activity or another trigger even though the muscles produce less force.
Treatment therefore needs to sit within a broader assessment rather than replace diagnosis or conservative care.
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A dentist should first work out where your pain comes from.
During the assessment, the dentist will ask about your symptoms, medical history and previous treatment. They will examine jaw movement and feel the chewing muscles for tenderness. They may also ask you to clench so they can assess the size and activity of the masseters.
Tooth wear, muscle tenderness or enlarged masseters can support a pattern of forceful clenching, but none of these findings proves the cause by itself.
Most patients start with conservative measures. Depending on the problem, these may include heat, jaw exercises, changes to habits that overload the jaw and a dental appliance where appropriate.
A dentist may discuss botulinum toxin when:
• pain persists despite conservative care
• the examination points to a strong muscular component
• overactive chewing muscles contribute to symptoms
• the patient understands that the benefit remains uncertain and temporary
Pain from a tooth, inflamed joint or structural TMJ problem needs separate assessment and treatment.
Your goals also matter. If injections into the masseter could alter the shape of your lower face, the dentist should discuss that possibility before treatment.
Before treatment, the dentist reviews your health, current medication and treatment goals. They should also discuss the expected effect, alternatives and possible complications.
The dentist examines the chewing muscles and may ask you to clench so they can identify the borders of the masseter. They then mark the injection sites and place small amounts of botulinum toxin into selected areas using a fine needle.
The effect develops over the following days as the treated muscle begins to contract with less force.
Studies report symptom relief lasting between about eight and 24 weeks, although individual responses vary. Some patients may notice little benefit. Others may experience improvement for several months.
A dentist should review your pain, jaw movement and muscle function before recommending another treatment.
Different botulinum toxin products use different units. Dentists cannot convert the dose from one product to another by treating the units as interchangeable.
The masseter contributes to the width and shape of the lower face. Bone structure, fat distribution and other soft tissues also affect your jawline.
People who clench heavily can develop thicker masseter muscles. When botulinum toxin reduces the force and activity of the muscle, the muscle fibres may shrink over the following weeks.
This process can reduce some of the bulk around the jaw angles.
The amount of change depends on your anatomy. A patient with large masseter muscles may notice more difference than someone whose jaw width comes mainly from the underlying bone.
Some patients like the softer appearance. Others do not want a visible change to their facial shape.
A dentist should discuss this possible effect before treatment. Pain relief and jaw function should remain the clinical reason for treatment when the injections form part of care for TMJ-related jaw pain.
Common short-term effects include bruising, tenderness and discomfort around the injection sites.
Reducing masseter activity can also make chewing feel weaker. If the toxin affects nearby muscles, you may notice facial asymmetry or a change in your smile.
These effects often improve as the action of the toxin wears off, although the severity and duration vary between patients.
The MHRA warns that botulinum toxin can spread beyond the injection area in rare cases. This can cause problems with swallowing, speech or breathing. Seek urgent medical attention if you develop difficulty swallowing or breathing after treatment. Slurred speech also requires urgent assessment.
Researchers have also examined whether repeated reduction of chewing-muscle activity could affect the mandible. Current evidence does not establish the long-term effect of repeated injections on mandibular bone health, so dentists should take repeated treatment into account when discussing risks.
UK product licences for botulinum toxin do not include TMJ-related jaw pain or TMD as approved indications.
A clinician who uses botulinum toxin for this purpose therefore prescribes it off-label.
Off-label prescribing allows an appropriately qualified clinician to use a licensed medicine outside its approved indication when they judge that treatment is clinically appropriate.
Your dentist should explain why they recommend the treatment, discuss other options and tell you about the limits of the evidence. They should also obtain and record informed consent.
A dentist providing the treatment needs appropriate training, must assess you in person and should hold suitable indemnity cover for the procedure.
Botulinum toxin may help selected patients whose pain around the TMJ comes largely from overactive chewing muscles and continues after conservative treatment.
A dentist should first identify whether the pain comes from the muscles, the joint, a dental problem or another source. If the chewing muscles appear to play a major role, botulinum toxin may form one part of the treatment plan.
Any reduction in masseter size or change in facial contour should form part of the consent discussion rather than drive treatment for jaw pain.
Botulinum toxin type A can reduce the force produced by the masseter and other chewing muscles. This may help some patients with persistent muscle-related pain around the TMJ, especially when conservative treatment has not provided enough relief.
Research has not shown a consistent benefit across all patients with TMJ-related pain. The effect also wears off, and injections carry risks ranging from temporary chewing weakness and bruising to rare problems with swallowing or breathing.
A dentist should identify the source of your pain before discussing treatment. If overactive chewing muscles appear to be a major contributor, you and your dentist can weigh the potential benefit against the uncertainty, temporary effect and possible change in facial shape.
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The art of great dentistry is here.
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