Tooth wear refers to loss of tooth substance by means other than dental caries. Tooth wear is a very common condition that occurs in approximately 97% of the population. This is a normal physiological process occurring throughout life; but with increasing lifespan of individuals and increasing retention of teeth for life, the incidence of non-carious tooth surface loss has also shown a rise. Tooth wear varies substantially between people and groups, with extreme attrition and enamel fractures common in archaeological samples, and erosion more common today.

Tooth wear is predominantly the result of a combination of three processes; attrition, abrasion and erosion. These forms of tooth wear can further lead to a condition known as abfraction, where by tooth tissue is 'fractured' due to stress lesions caused by extrinsic forces on the enamel. Tooth wear is a complex, multi-factorial problem and there is often difficulty identifying a single causative factor. However, tooth wear is often a combination of the above processes. Many clinicians, therefore, make diagnoses such as "tooth wear with a major element of attrition", or "tooth wear with a major element of erosion" to reflect this. This makes the diagnosis and management difficult. Therefore, it is important to distinguish between these various types of tooth wear, provide an insight into diagnosis, risk factors, and causative factors, in order to implement appropriate interventions. Tooth wear evaluation system (TWES) may help determine the most likely aetiology of tooth wear. Heavy tooth wear is commonly found on the occlusal (chewing) surface, but non-carious cervical lesions from tooth wear are also common in some populations.

Multiple indices have been developed in order to assess and record the degree of tooth wear, the earliest was that by Paul Broca. In 1984, Smith and Knight developed the tooth wear index (TWI) where four visible surfaces (buccal, cervical, lingual, occlusal-incisal) of all teeth present are scored for wear, regardless of the cause. A more recent index Basic Erosive Wear Examination (BEWE) from 2008 by Bartlett et al., is now also in use.

Attrition is loss of tooth substance caused by physical tooth-to-tooth contact. The word attrition is derived from the Latin verb attritium, which refers to the action of rubbing against something. Attrition mostly causes wear of the incisal and occlusal surfaces of the teeth. Attrition has been associated with masticatory force and parafunctional activity such as bruxism. A degree of attrition is normal, especially in elderly individuals.

Abrasion is loss of tooth substance caused by physical means other than teeth. The term is derived from the Latin verb abrasum, which means ‘to scrape off’. It tends to present as rounded ditching around the cervical margins of teeth, commonly described as ‘shallow’, concave or wedge shaped notches. Causative factors have been linked to this condition and include vigorous, horizontal tooth brushing, using toothpaste with a relatively high RDA value (above 250), pipe smoking or nail biting. It has also been shown that improper use of dental floss or Toothpicks can lead to wear on the interproximal (in-between) surfaces of the teeth.

Erosion is chemical dissolution of tooth substance caused by acids, unrelated to the acid produced by bacteria in dental plaque. Erosion may occur with excessive consumption of acidic foods and drinks, or medical conditions involving repeated regurgitation and reflux of gastric acid. It is derived from the Latin word erosum, which describes the action ‘to corrode’. This is usually on the palatal (inside) surfaces of upper front teeth and the occluding (top) surfaces of the molar teeth. Dental erosion is rarely seen in the archaeological record, but certain cases have been described which suggested acidic fruits and/or plants were regularly consumed.

Abfraction is a form of noncerious cervical lesion, where there is a loss of tooth substance at the cervical margins, purportedly caused by minute flexure of teeth under occlusal loading. This occlusal loading is one factor that interacts with chemical, biological, and behavioral factors in which result in this abfraction. The term is derived from the Latin words ab and functio meaning ‘away’ and ‘breaking’ respectively. Abfraction presents as triangular lesions along the cervical margins of the buccal surfaces of the teeth where the enamel is thinner and therefore, in the presence of occluding forces, is prone to fracture. Whether abfraction exists or not is debated.

Tooth wear indices are useful tools for carrying out epidemiological studies and for general use in dental practices.