Abfraction is the loss of tooth structure from flexural forces. This has not been supported yet by dental research but it is hypothesized that enamel, especially at the cementoenamel junction (CEJ), undergo this pattern of destruction by separating the enamel rods.
As teeth flex under pressure, the arrangement of teeth touching each other, known as occlusion, causes tension on one side of the tooth and compression on the other side of the tooth. This is believed to cause V-shaped depressions on the side under tension and C-shaped depressions on the side under compression.
This theory does not fully satisfy many researchers because there are many teeth whose occlusion causes tension and compression on either side. Consequently, it would be expected that many more teeth would show signs of abfraction, but this is not the case. Research is ongoing to identify the role abfraction has on this pattern of tooth destruction.
Abfraction lesions will generally occur in the region on the tooth where the greatest tensile stress is located. In statements such as these, there is no comment on whether the lesions occur above or below the CEJ. One theory suggests that the abfraction lesions will only form above the CEJ. However, it is assumed that the abfraction lesions will occur anywhere in the cervical areas of affected teeth. It is important to note that studies supporting this configuration of abfraction lesions also state that when there is more than one abnormally large tensile stress on a tooth two or more abfraction lesions can result on the one surface.
When looking at abfraction lesions there are generally three shapes in which they appear, appearing as either wedge, saucer or mixed patterns. Wedge and saucer-shaped lesions are the most common, whereas mixed lesions are less frequently identified in the oral cavity. Wedge-shaped lesions have the sharpest internal line angles and saucer/mixed-shaped lesions are either smooth internally, or a variety.
Clinically, people with abfraction lesions can also present with tooth sensitivity in the associated areas. This occurs because as the abfration lesions appear, dentine/cementum is exposed. The dentine and cementum are less dense than tooth enamel and therefore more susceptible to sensation from thermal/mechanical sources.