Trismus after dental injection is most likely due to involvement of which area or structures?

Trismus after dental injection is most likely due to involvement of which area or structures?

• A. Infratemporal fossa muscles and vessels
• B. Orbit
• C. Mandible condyle only
• D. Submandibular space

Answer: (A)

Trismus after a dental injection is most often due to irritation or trauma to the muscles of mastication located in the infratemporal fossa, especially the lateral and medial pterygoid muscles. When a needle or injected material reaches this area, it can cause inflammation, edema, or a hematoma that irritates these muscles or their motor nerve fibers, leading to painful muscle spasm and a limited ability to open the mouth. The infratemporal fossa houses these muscles and the vessels that can be affected during injections, making it the most likely source of post-injection trismus. The orbit is distant from the injection sites and would not produce trismus. Involvement of the mandible condyle alone doesn’t typically explain the common pattern of limited mouth opening after injections, and submandibular space issues tend to present with swelling and floor-of-mouth concerns rather than primary muscle spasm.

Trismus after a dental injection is most often due to irritation or trauma to the muscles of mastication located in the infratemporal fossa, especially the lateral and medial pterygoid muscles. When a needle or injected material reaches this area, it can cause inflammation, edema, or a hematoma that irritates these muscles or their motor nerve fibers, leading to painful muscle spasm and a limited ability to open the mouth. The infratemporal fossa houses these muscles and the vessels that can be affected during injections, making it the most likely source of post-injection trismus.

The orbit is distant from the injection sites and would not produce trismus. Involvement of the mandible condyle alone doesn’t typically explain the common pattern of limited mouth opening after injections, and submandibular space issues tend to present with swelling and floor-of-mouth concerns rather than primary muscle spasm.