Attrition, erosion, abrasion and abfraction: the four ways teeth wear.

Wear usually shows first on the front teeth, because they are the teeth you see. Grinding leaves their edges flat and shorter, and when the jaw slides forward the upper and lower edges fit each other like matching pieces ^[2]. Acid thins the edges until they look see-through and can chip, and leaves the surfaces smooth and glassy ^[10][26]; with vomiting, it shows mostly on the inner side of the upper front teeth, where you cannot see it ^[23]. Small matching notches in the edges of an upper and a lower front tooth have been linked with cracking sunflower seeds between them ^[22].

Further back, brushing wear can show as a notch at the gum line, which may be sensitive ^[1][10], and old fillings that stand above the tooth around them point to acid ^[2]. Some wear comes with age and is not a problem in itself ^[2]. What matters is which kinds are at work, how fast they are going and why, and that is what an examination works out.

A worn tooth carries clues to how it was worn. When teeth grind against each other they wear flat, with smooth, shiny facets that have sharp edges and fit a facet on the opposing tooth; on the front teeth this shortens the edges, on the back teeth it flattens the cusps; this is attrition ^[2]. Acid works differently: it softens and dissolves the surface, so the tooth loses its natural shape, with cupped cusps and shallow hollows wider than they are deep, a rim of enamel may survive next to the gum, and an old filling can be left standing above the tooth around it; this is erosion ^[2][26]. Abrasion is wear from something other than a tooth, most often a brush and paste, and at the neck of the tooth it can form a notch ^[1]. Abfraction is the name for a notch thought to come from bite forces bending the tooth, and the FDI World Dental Federation's policy statement notes that the term has been questioned ^[1].

These four rarely act alone. A review of the evidence found that the most important interaction is acid softening the surface so that brushing wears it away faster, and that this seems to drive much of the wear on biting surfaces and at the neck of the tooth ^[3]. Wear is common here: in a 2026 study of 876 teenagers in the UAE, almost all had some, and drinking sports drinks weekly or daily was linked to higher scores ^[12].

Wear builds up slowly, stage by stage. A worn biting surface is graded by how much of the crown's height has gone: wear within the enamel; dentine showing, with up to a third lost; a third to two thirds; and two thirds or more ^[27]. The European consensus calls wear severe once at least a third of the crown has been lost ^[25]. How long a tooth takes from one stage to the next varies from person to person and has not been measured in years, which is why the slider below moves through stages, not time.

Each stage changes what, if anything, needs doing, from keeping an eye on it to rebuilding the worn surfaces, and the slider shows what each stage usually needs. How each stage is treated, and why finding the cause comes first at every stage, is explained in detail on the tooth wear treatment page.

A notch where the tooth meets the gum, sometimes called a wedge-shaped defect, is the kind of wear most people notice, because it is sensitive, because food catches in it, or because it looks darker than the tooth around it. These notches sit on the cheek side far more often than on the tongue side ^[21] and are common on premolars: in one clinical study of notches chosen for filling, nearly half were on premolars and most were 1 to 2 mm deep ^[4]. They come in several looks: rounded grooves, right-angled wedges, flat-floored notches, sharp wedges and narrow clefts, sometimes stacked one above another or reaching under the gum.

The classic teaching links rounded notches to brushing and sharp wedges to bite forces. The evidence is less tidy. In the laboratory, brushing alone, with no bite at all, produced wedged, mixed and rounded notches ^[19], and in another laboratory study the same brushing made sharp wedges on its own but wide, open dishes when acid was added, and with acid the notches grew faster ^[5]. A review concluded that the shape of a notch does not predict its cause ^[6]. Abfraction has support from laboratory models but no proof in patients ^[7][3], and an international consensus found no evidence that heavy bite forces cause these notches ^[8].

Cracking sunflower seeds between the front teeth is a common snack habit in many countries, including the Middle East. Small rounded or V-shaped notches, about 1 to 2 mm deep, have been reported in the edges of the front teeth where the seed is held, most often in an upper central incisor and often with a matching notch in the tooth below; some people also had fine cracks, chipped edges or sensitivity ^[22].

The evidence so far is case reports and small series, so the seeds count as a possible contributor rather than a proven cause, and other habits that hold something between the same teeth, such as biting pens, nails or pins, are asked about as well ^[22]. Shelling the seeds by hand, or buying them shelled, keeps the teeth out of it, and a notch that is sensitive or bothers you can be rebuilt with tooth-coloured filling material ^[22].

Because the look of the wear does not prove its cause, the assessment starts with the story behind it: drinks and diet, reflux or vomiting, how and how hard you brush, grinding or clenching, habits such as cracking seeds, and medicines that dry the mouth. The teeth are then recorded with photographs and scans, so that later visits can measure change rather than guess at it. Slow wear takes time to show: changes smaller than about a twentieth of a millimetre are hard to detect, and visible change can take 18 months to two years ^[20].

When the bite is part of the picture it is examined, but a notch on its own is not a reason to adjust the bite: in a trial, adjusting the bite did not slow notches over 30 months ^[9]. Teeth do keep moving slowly through adult life, about a third of a millimetre over 16 years in one long study ^[15], but that is not the tooth growing back. A night guard can protect teeth from grinding, yet no study has shown that it treats a notch ^[10]. It is also worth knowing about snoring or sleep apnoea before one is made, because in a small trial an upper guard slightly increased breathing pauses in people who had apnoea ^[17], and guards that cover only some of the teeth can let teeth move ^[16].

Most of the work is on the causes: changing how and when acidic drinks are taken, treating reflux with your doctor, brushing gently with a soft brush and a low-abrasive paste, and protecting the teeth when grinding is confirmed. There is no evidence that a filling stops a notch from growing ^[10], so a notch is watched while the causes are dealt with, and restored for a reason: sensitivity that does not settle, a weakened tooth, food trapping, or its appearance ^[10][18]. When a notch is filled, it is bonded under rubber dam, with the clamp that holds the dam seated gently, and shaped flush with the tooth: in a five-year trial, gum recession was far more common next to fillings whose edges did not fit flush, and somewhat more common where the dam had been held with a retraction clamp ^[14].

Worn front teeth can be built back up when they need it, often with composite bonded onto the worn edges, which keeps cutting to a minimum: the European consensus on severe wear advises putting restorations off until they are needed and keeping them conservative ^[25]. In one study of 34 people with severe wear, composite on the front teeth failed at most 2.2 per cent a year over about five years ^[24].

When the gum has also moved back, the plan is made together with the periodontist on the team. A shallow hollow on the root can be covered by gum treatment alone, with no filling; a deeper notch that has taken the enamel edge is filled first, only as far as the gum cannot cover, and then the gum is treated ^[13].