We use Botulinum toxin injections to help reduce the bulk of the masseter muscle to shape the face. Botulinum toxin injections into the masseter muscle is also a cure for teeth grinding. Strong masseter muscles. A wide jaw gives rise to strong masseter muscles which in turn produces a square, masculine face. This can be unflattering for some women. Botulinum toxin injected into the masseter muscle will relax this muscle and therefore slim the face.