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.
Characteristic Features: Development of a facet (flat surface with circumscribed and well defined border). Opposing tooth facets will match perfectly in occlusion.
Interproximal Attrition: Occurs at proximal surfaces of adjacent teeth when they move against one another on occlusal loading. Movement of teeth is in the vertical direction.