This patient was obsessed with brushing his teeth. He used a hard toothbrush and toothpaste and sat in front of the TV brushing back and fourth for fifteen minutes at a time. The hole you see in the depth of the notch is actually the nerve canal. The gums are swollen around the tooth as a result of the abscess, and we were unable to retract them further to show the full extent of the notch. the shape of the notch is typical of toothbrush abrasion. There is generally a sharp drop in the tooth structure where the hard enamel stops, and the softer root begins. The drop-off gradually subsides as the root approaches the gums. The gums are always under attack from the toothbrush, but they can rebuild themselves thus protecting the root underlying them from damage. They eventually loose the battle, but their gradual decline accounts for the gradual drop-off in tooth structure as the notch descends toward the gum line.
While this is the reason that dentists and hygienists always recommend that a patient use a soft toothbrush, years of research have shown that overly vigorous application of toothpaste (Many brands, including some of the most popular ones) may be a more important factor than the hardness of the brush in producing these lesions.
In order to avoid this type of tooth damage, it is recommended that patients learn to use the the more gentle technique discussed on my page on prevention, and to use mouthwash on their toothbrush instead of toothpaste.
The image above is from a patient who presented to my office with a toothache in the lower left second premolar, the leftmost tooth in this image. He was a serious brusher and used a hard toothbrush causing severe toothbrush abrasion in both premolars. These lesions had been filled with composite about five years before this picture was taken, but since there was no tooth behind the second premolar, the patient had succeeded in actually brushing away the composite filling the defect. He continued brushing away until he had exposed the nerve in the center of the tooth. The hole you see close to the gums is the space where the nerve used to live. Some research has shown that this type of damage does not happen if there is no toothpaste on the toothbrush.
The “Coke bottle” tooth image above, as well as the one below shows extensive erosion of the cervical (around the gum line) tooth structure often attributed to abfraction. This may, in fact, be the case, however evidence suggests that it is more likely to be due to overzealous tooth brushing with toothpaste.
The images below show extensive damage to enamel. Many dentists believe that this is likely to be due to abfraction (see below), however, toothpaste abuse alone may be the culprit. In defense of the toothpaste abrasion theory, note the extreme smoothness and polishing of the lesions.
The theory of abfraction
In the early 1990’s, a dentist named J. O. Grippo concluded that cervical erosions were the result of flexing of the teeth at the gum line due to heavy bruxing (grinding). This flexure resulted in damage to the enamel rods at the gum line resulting in their loosening and consequent flaking away of the tooth structure. He named this type of damage abfraction in a paper published in 1991 (Grippo JO. Abfractions: a new classification of hard tissue lesions of teeth. J EsthetDent 1991; 3:14-19.)
The theory of abfraction postulates that very hard bruxing forces on the occlusion causes the teeth to deform and bend on a microscopic level. Nearly all the research on the relationship of occlusal forces (bruxing) to cervical lesions shows that teeth do, indeed flex in the cervical region under bruxing loads, but none seems to cite actual damage caused by this deformation without an abrasive or erosive component applied as well. Nevertheless, the abfraction theory argues that bruxing forces alone can cause an erosion of the enamel that protects the teeth on the buccal surface near the gum line. It is postulated that abfraction is responsible for chronic sensitivity of the teeth to cold foods and liquids. This biomechanical theory implies that damage like that seen in the images below would be difficult to repair with bonded fillings because the repair would tend to pop off after a while due to the constant deformation of the tooth caused by bruxing.
In reality, however, it is likely that abfractive flaking of the enamel tends to weaken the bond of the enamel rods to the dentin and allows a toothbrush and toothpaste to abrade the loosened enamel more easily. Thus abfraction and toothbrushing work together to produce the damage to the enamel you see in the images below.
Martin S. Spiller, D.M.D.
Note the difference between these images and the ones that preceeded them. They are examples of abfraction. Abfraction affects enamel more than does toothbrush abrasion, which has more of an effect on the dentin of the root.
Note also in the image above how shiny the teeth are. The patient has literally scrubbed off all the surface anatomy from his teeth with his toothbrush and toothpaste. But also notice that the abfraction of the enamel stops at the lateral incisor and does not cause appreciable damage to the central. This is probably because the more intense toothbrush scrubbing takes place in the distal sextant of the right maxilla. Most dentists have noted that patients tend to have more toothbrush abrasion in one particular area of the mouth than others. This is due to the habit of brushing harder or with more aggression in one area than others.