Abstract
In clinical dentistry, botulinum toxin is generally used to treat the square jaw, bruxism, and temporomandibular joint diseases. Recently, this procedure has been expanded and applied for cosmetic purposes, and it is becoming a key task to be aware of the precise anatomical structure of the target muscles to be cautious during treatment and how to prevent side effects. Therefore, the purpose of this study is to observe the anatomical structure of the superficial layer of masseter muscle and to provide a most effective botulinum toxin injection method through clinical anatomical consideration. It was observed that the muscle belly of superficial part of the superficial layer was originated from the deep to the aponeurosis of masseter muscle and descend, then changed gradually into the tendon structure attaching to the inferior border of the mandible. In this study, we named this structure deep inferior tendon. This structure was observed in all specimens. We conclude that the use of superficial layer and deep layer injection should be considered to prevent paradoxical masseteric bulging in consideration of the deep inferior tendon of superficial part of superficial layer of masseter muscle.
