A wide or heavy-set jaw can often result from the enlargement of the masseter muscles. These muscles sit over the jaw and become noticeable when clenching the back teeth. In some individuals, whether due to genetics or frequent jaw clenching, the masseters can enlarge. This enlargement can lead to the lower part of the face appearing wider and more masculine. Botulinum toxin, often referred to as 'Botox,' injections can help reduce the size of the masseter muscles, safely and effectively slimming the width of the jaw and creating a more slender lower face.