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     Tooth mobility
     Some tooth mobility in a labiolingual plane can be elicited in healthy, single-rooted teeth, especially lower incisors, being more mobile than multirooted teeth. Increasing tooth mobility is produced by,
     l. Spread of inflammation from the gingiva into the deeper tissues
     2. Loss of supporting tissue
     3. Occlusal trauma.
     Mobility also increases after periodontal surgery and in pregnancy. In periodontal pathology tissue destruction is always accompanied by inflammation and frequently by occlusal trauma. Mobility, which is produced by inflammation and occlusal trauma, is reversible, as demonstrated by the reduction in mobility following scaling and occlusal adjustment; mobility associated with destruction of supporting tissue is not reversible.
     Assessment of mobility for research purposes can be made using special apparatus but clinical assessment is usually subjective. It is elicited by exerting pressure on one side of the tooth under examination with an instrument or finger tip while placing a finger of the other hand on the other side of the tooth and its neighbour which is used as a fixed point so that relative movement can be discerned. Another way of eliciting mobility (although not assessing it) is to place fingers over the facial surfaces of the teeth while the patient grinds the teeth.
     The degree of mobility may be graded as follows:
     Grade l. Just discernible
     Grade 2. Easily discernible and up to l mm labiolingual displacement
     Grade 3. Over l mm labiolingual displacement, mobility of the tooth up and down in an axial direction.

     Tooth migration
     Movement of a tooth (or teeth) out of its original position in the arch is a common feature of periodontal disease and one which alerts the patient to the problem. A balance of tongue, lip and occlusal forces maintains tooth position in health. Once supporting tissue is lost these forces determine the pattern of tooth migration. The incisors move most frequently in a labial direction but teeth may move in any direction or become extruded. Once a tooth migrates the force on that tooth changes and this may promote further stress and further migration. If an upper incisor migrates labially the lower lip may come to lie lingual to the incisal edge of the tooth and produce further migration.

     Discomfort
     One of the most important features of chronic periodontitis is the almost total absence of discomfort or pain unless acute inflammation supervenes. This is one of the main distinctions between periodontal and pulp disease. Discomfort or pain on percussion of the tooth indicates some active inflammation of the supporting tissues, which is at its most acute in abscess formation when the tooth becomes exquisitely sensitive to touch. Sensitivity to hot and cold is sometimes present when there is gingival recession and root exposure. Indeed one common clinical experience is the appearance of sensitivity, especially to cold, when roots once covered in calculus are cleaned. On occasion p