Some individuals may naturally have a well-developed masseter (jaw) muscle, which can give the face a wide or square appearance, resulting in a masculine and angular look. Injecting botulinum toxin into the masseter muscle, can cause a reduction in size, leading to an improvement in facial shape and slimming of the lower face, without affecting any chewing function.

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This treatment can also be used to alleviate the pain from bruxism (involuntary teeth grinding).