The horizontal or vertical displacement of a tooth beyond its normal physiological boundaries. It may be due to trauma, periodontal disease, occlusal traumatism, or loss of alveolar bone support. Tooth mobility may be assessed by applying alternate pressure on the outer and inner aspects of the crown of the tooth using two hand instruments, but this assessment is very operator-dependent. The results can be recorded using a mobility index.Mechanical instruments for measuring mobility more accurately have been developed, such as the Periotest ® which uses an accelerometer to measure the resistance of the tooth to a force applied 16 times over a 4 second period. Vertical tooth movement may be detected on the occlusion of the tooth (fremitus).
A tooth mobility index
Detectable movement of up to 0.2mm.
Horizontal movement of the crown between 0.2 and 1.0mm.
Horizontal movement of the crown greater than 1.0mm.
Horizontal movement of the crown greater than 1.0mm and additional vertical movement.