Firstly, Attrition. Attrition is a form of regressive change in teeth characterized by wear of tooth substance or restoration as a result of the tooth to tooth contact during occlusion, mastication or parafunction. Mostly, attrition is an age-related physiological process whose rate and severity depends on several factors like diet quality, dentition, masticatory force and chewing habits. So, older individuals often exhibit more attrition than the younger ones.
Attrition may also be pathological which may be caused either due to:
a. Abnormal occlusion - leading to traumatic contact during chewing which causes more tooth wear
b. Premature extraction of teeth - which causes attrition of remaining teeth as the occlusal load on these teeth increase after the extraction of teeth because the masticatory force of an individual remains constant.
Also, pathological attrition may be due to parafunctional chewing habits like bruxism and habitual chewing of coarse and abrasive foods or other substances like tobacco and betel nut.
Abrasion: It is the pathological wearing of tooth structure or dental restorations by friction with foreign substances independent of occlusion. Toothbrush abrasion is the commonest type of abrasion caused by faulty toothbrushing technique, excessive force during tooth brushing and a dentrifice with strong abrasive. Abrasion may also be caused by habitual chewing of betel nut. tobacco and Pan (betel quid), and also by faulty clasp design in removable partial denture prosthesis. Tailors, carpenters, hairdressers, and shoemakers who use their teeth to hold nails and pins also develop abrasion.
Erosion: It is the progressive irreversible loss of hard dental tissues by some chemical process that doesn't involve bacterial action. It may be caused due to extrinsic factors such as acidic foods and beverages, medications ( Vitamin C and Hydrochloric acid preparations) and occupational exposure to acidic vapors. Intrinsic factors causing erosions are systemic diseases like Bulimia, GERD (Gastroesophageal reflux disease), etc. which cause increased vomiting and regurgitation of bowel contents into the mouth.
Abfraction: It is the pathological loss of tooth structure caused by biochemical loading forces. Excessive force during chewing or clenching cause repeated flexure of tooth and cause ultimate material fatigue and wearing off of tooth away from the point of loading.