Which muscle can be injected with a cavity fluid injection to reinforce mouth closure?

Which muscle can be injected with a cavity fluid injection to reinforce mouth closure?

• A. Sternocleidomastoid
• B. Masseter
• C. Temporalis
• D. Corrugator

Answer: (B)

Targeting the muscle that directly closes the jaw is the key idea. The masseter is the strongest elevator of the mandible and its contraction pulls the lower jaw upward to close the mouth. Injecting cavity fluid into this muscle helps firm the tissue and maintain a closed, natural-looking mouth after the body is prepared. The other muscles listed don’t serve this primary function for mouth closure: the sternocleidomastoid is a neck mover, not involved in keeping the lips shut; the temporalis does assist in jaw closure but is smaller and less convenient for injection purposes; and the corrugator is an eyebrow muscle with no role in closing the mouth. So the masseter provides the most reliable means to reinforce mouth closure with cavity fluid.

Targeting the muscle that directly closes the jaw is the key idea. The masseter is the strongest elevator of the mandible and its contraction pulls the lower jaw upward to close the mouth. Injecting cavity fluid into this muscle helps firm the tissue and maintain a closed, natural-looking mouth after the body is prepared. The other muscles listed don’t serve this primary function for mouth closure: the sternocleidomastoid is a neck mover, not involved in keeping the lips shut; the temporalis does assist in jaw closure but is smaller and less convenient for injection purposes; and the corrugator is an eyebrow muscle with no role in closing the mouth. So the masseter provides the most reliable means to reinforce mouth closure with cavity fluid.