Trismus after injection of local anesthetic.

Persistent pain at the site of injection is the most common complication of local anesthesia in the oral cavity. The complication of trismus after local anesthetic injection is rare and may be prevented by the use of short needles for maxillary posterior injections, and by the avoidance of multiple injections in a short period time. Once trismus develops, its progression to chronic hypomobility and fibrous ankylosis may be prevented by the early institution of treatment consisting of heat, analgesics, muscle relaxants, and exercises.