Figure shows the clinician grasping a tooth between his thumb and forefinger at the level of the middle third of the crown. This is:

Percussion is one of the oldest pulp vitality tests used because it requires no armamentarium. Generally, patients who have a tooth sensitive to mastication have already percussed the tooth in question with their own finger tip(s) and informed the dentist which teeth are sensitive. Percussion is an indirect means of testing pulp vitality, because teeth that are sensitive to percussion often have existing periapical lesions associated with a necrotic pulp. However, this is not always the case, and false positives can result if the clinician is evaluating a cracked tooth or a ‘‘high’’ restoration. If a crack has developed in the crown of a tooth with a vital pulp, the tooth can still be exquisitely sensitive, because of the crown segments moving microscopically causes pain due to the movement of fluid in the odontoblastic tubules. The tooth is sensitive to thermal stimuli as the pulp is vital. These mutually exclusive diagnostic findings, pain to percussion/mastication and thermal sensitivity, are pathognomonic for a cracked tooth.