Attrition is the loss of teeth structure by mechanical forces from opposing teeth. Attrition initially affects the enamel and if unchecked, may proceed to the underlying dentin. Once past the enamel, attrition quickly destroys the softer dentin. Gradually it affects the whole teeth.
The most common cause of attrition is bruxism. Functional habits are those such as chewing and swallowing, which usually puts very little force on opposing teeth. Parafunctional habits, such as clenching and clicking the teeth together nervously, place greater amounts of forces on opposing teeth and begin to wear the teeth. As expected, wear usually begins on the incisal or occlusal surfaces.