ABSTRACT
Botulinum toxin has been widely used for masseteric hypertrophy, which is usually idiopathic and can be attributed in some cases to bruxism and habitual jaw clenching. The prevalence of the masseteric hypertrophic problem appears greater in some areas like Korea. Genetic factors and dietary habits are postulated to be the reason. Deep injection of the masseter muscle has often been emphasized to avoid the spread to the risorius muscle, which has its origin quite superficially about the masseter and parotid fascia. Injection should be limited to the lower third of the muscle to lessen the incidental effect additionally on the risorius and parotid gland. In addition to the recognition of endplate zone distribution, some anatomical studies find the arborization of the masseteric nerve looks denser in the middle inferior section under a special stain. The ultimate goal of masseter treatment is the shape, not the quietness, of the muscle. An artistic approach should be adopted when giving toxin.
