attrition /ətrish″ən/ [L, atterere, to wear away] , 1. the process of wearing away or wearing down by friction. 2. the physiological wearing away of the teeth such as from normal mastication, grinding, bruxism, premature contacts, or abnormal tooth structures. See abrasion, abfraction, erosion. 3. a reduction in the number of participants in a study or program of study that happens when individuals withdraw or are dismissed.
