A pulp tester is a diagnostic device used to determine whether the dental pulp—the soft inner tissue of a tooth containing nerves and blood vessels—is alive or damaged. The device delivers a small, controlled electrical stimulus to the tooth surface. If the patient feels a sensation, it indicates that the nerve inside the tooth is still vital. This test is useful when diagnosing tooth pain, trauma, deep cavities, or before performing root canal treatment. It helps dentists decide whether a tooth can be preserved or requires endodontic therapy.