Botulinum toxin injected into the chewing muscle reduces force and eases symptoms. It does not remove the cause of clenching, though; who it suits and who it does not.
A frequently discussed option in the treatment of night-time clenching is botulinum toxin injected into the chewing muscle. It gives clear relief in some patients; a decision made without knowing what it does and does not do, however, can turn into an unnecessary procedure.
How it works
Botulinum toxin temporarily blocks the signal travelling from nerve to muscle. The muscle is not fully paralysed; the force it can produce falls. Injected into the masseter, the powerful chewing muscle, it clearly reduces the load placed on the teeth during clenching.
The logic is to soften the consequence rather than stop the behaviour. The patient continues to clench, but the force produced no longer strains the teeth and joint as before.
When it is considered
Botulinum toxin is not a first-line treatment. A night guard, habit modification, physiotherapy and a review of triggers are tried first. It arises as an additional option in patients who do not respond adequately to those steps.
- Severe muscle pain persisting despite a splint
- Patients who physically cannot tolerate a splint
- Repeated fractures of restorations from very strong clenching
- Widening of the face from marked muscle enlargement
The aesthetic effect is a separate matter
In long-standing clenchers the masseter enlarges and the lower face widens, giving the jaw line a square appearance. Botulinum toxin thins that muscle over time and narrows the lower third of the face.
For some patients this is a welcome outcome; for others an entirely unexpected change. Both the medical and the aesthetic result should be discussed together when deciding; they cannot be separated.
How long the effect lasts
The effect usually begins within a week of the injection and is fully established within two. Its duration varies with the person and the dose, but runs from three to six months. The muscle then gradually returns to its former strength.
This temporary nature is both an advantage and a drawback. If the result is not liked it is not permanent; if it helps, however, the treatment must be repeated. The dose can usually be reduced at subsequent sessions.
Risks and side effects
It is safe when given at the right dose and the correct anatomical point. An injection placed incorrectly can affect neighbouring muscles, producing asymmetry in the smile or a greater than expected loss of chewing power.
Permanent reduction in muscle mass and, rarely, bony changes have been reported with long-term, high-dose repetition. It is not used in pregnancy, breastfeeding or certain neuromuscular conditions.
Does it replace a splint?
No. Botulinum toxin reduces force but does not stop the teeth touching. If grinding continues, contact wear continues too. The two are therefore planned together in most patients: the splint prevents contact, the toxin lowers force.
Relying on the toxin alone can make the wear invisible while it continues. The patient feeling better does not mean the problem is solved; this is why review appointments matter.
The cause remains in place
Behind night-time clenching lie sleep fragmentation, stress, caffeine and alcohol, smoking and sometimes sleep apnoea. Botulinum toxin touches none of these. Because the patient feels better afterwards, investigating those factors is often postponed.
Where there is snoring and daytime sleepiness in particular, a sleep assessment should not be neglected. Treating an underlying sleep disorder can markedly reduce clenching, and that is the only lasting solution.
Who should carry it out
Injecting the chewing muscles requires command of facial anatomy and muscle function. The borders of the masseter, the salivary gland beside it and the muscle groups that produce a smile lie very close together; a few millimetres' deviation in the injection point changes the result.
The procedure should therefore be planned by a clinician who works with the chewing system and can also manage splint therapy where needed. Treating it as part of a whole plan for the chewing system, rather than in isolation, determines the outcome.
How to decide
The correct order is diagnosis first, then conservative treatment, then additional options where there is no response. At examination the degree of wear, muscle tenderness and joint findings are recorded; without that record there is no way to measure whether treatment worked.
Where the treatment is requested for aesthetic reasons alone, without a medical indication, that should be stated openly. Treating clenching and slimming the face are not the same procedure, and the expectation must be clear from the start.
