Local Anesthesia Evaluator Practice Exam

Trismus after local anesthetic injection is most often caused by trauma to the jaw muscles (such as the masseter or pterygoid muscles) or a small hematoma from the injection, which irritates the muscle and triggers a painful spasm that limits opening. The best approach is conservative and focused on the muscle: warm compresses help relax the spasm and increase blood flow, gentle jaw opening and stretching exercises restore range of motion and prevent stiffness, and analgesics control pain and inflammation. This targets the usual cause directly and avoids unnecessary treatments. If infection or nerve injury were present, the signs and management would be different (infection with fever or swelling, or numbness/weakness from nerve damage), and dehydration would not explain a localized jaw syndrome.