Erosion – acid attack can dissolve the surfaces of the teeth. Acid can come from outside sources (like the things we eat/drink), or can come from sources within the body (like gastric reflux or vomiting).
Abrasion – using the teeth to eat abrasive and hard foods can wear the surfaces of the teeth away.
Attrition – grinding habits can strip the surfaces of the teeth as they keep scraping against each other. Grinding can exert up to 80 kilograms of force on teeth!