The five major causes of pathologic, non carious tooth wear
- Toothpaste Abuse
- Soda Swishing (Coke Swishing, Pepsi Swishing, etc.)
- Fruit Mulling
The theory of abfraction suggests that the cervical buccal lesions were caused by the biomechanical “bending” of the teeth due to severe bruxing forces.
In the following pages, I hope to show that there are really five major causes of non carious tooth wear, and abfraction, if it is even a real factor, plays only a minor part in the drama.
His conclusions were based on both observation and experiment. He concluded that these notch-like cervical erosions were caused by vigorous tooth brushing in combination with abrasive tooth powders.
Interestingly, GV Black, who is widely considered the father of modern dentistry disagreed with Miller, and even traveled to England to see his work. Black had to agree that many of Millers experimentally produced lesions looked like the erosions he had been studying, but remained skeptical. Black eventually published a paper, based on observation alone refuting Miller’s conclusions. Unfortunately, Miller died before he could respond to Black’s paper, and the origin of cervical erosions has remained controversial ever since.
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.)
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 the erosion of the tooth structure on buccal surface, especially in the cervical region, that every dentist and hygienist is familiar with. 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.
Many dentists dispute the theory of abfraction, blaming this type of damage on what is commonly called “toothbrush abrasion”. This harks back to the early work of W.D. Miller in 1917, however it has been confirmed by more recent studies by T.C. Abrahamson which have shown that toothpaste (not the toothbrush) is abrasive enough to cause this type of damage if the patient is too aggressive in brushing the teeth in a very hard and vigorous “sawing” motion. Abrahamson suggests that the term “toothbrush abrasion” be replaced with the term “toothpaste abuse“.
His studies using mechanical “tooth brushing” machines have shown that the toothbrush alone does not cause the type of tooth damage shown here, but the addition of toothpaste to the bristles does! (Toothbrushes without toothpaste do cause soft tissue damage and indeed, overly vigorous tooth brushing without toothpaste leads to gingival recession.) The current support for the theory of abfraction, as opposed to theory of toothbrush abrasion may be due, at least in small measure to the considerable influence of toothpaste manufacturers who actually did much of the original work showing the damage that toothpaste could do to teeth, but suppressed the results for obvious reasons.
Dental Thermal Hypersensitivity
Proponents of the theory of abfraction postulate that dental hypersensitivity to cold is due to abfractive removal of tooth structure at the cervix of the tooth due to bruxing. Opponents would argue that most dental thermal hypersensitivity is due to erosion of tooth structure because of toothpaste abuse.
The evidence against the theory of abfraction is as follows:
The theory of abfraction is based primarily on engineering analyses that demonstrate theoretical stress concentration at the cervical areas of teeth. While there are a number of studies linking occlusal forces to tooth flexure, few controlled studies exist that demonstrate the relationship between occlusal loading and abfraction lesions.
Most of the damage of this nature is to the buccal surfaces of the teeth, with little erosion to lingual surfaces. If flexure of the teeth were causing this problem, it seems likely that we would see equal damage to both buccal and lingual surfaces.
There is little or no evidence of these lesions in prehistoric skulls, even though the teeth show considerable occlusal (chewing surface) wear from mulling tough and fibrous foods. All the cervical erosions found in historic skulls seem to begin after the invention of tooth powders and toothbrushes in the 16th century.
The lesions tend to be much worse on the buccal surfaces of the premolars and the canines where patients are likely to place the most brushing force. It becomes progressively worse as one proceeds from the posterior teeth to the anteriors. Furthermore, the most affected teeth tend to be in buccal version. The teeth in which linguals are affected are mostly found mesial to an edentulous space (like the one shown in the image below).
The damage seems to stop at the gingival crest instead of at the crest of the bone, which is where the theory of abfraction suggests the flexure should be the worst. The gingiva heal daily protecting the root of the teeth from the toothbrush and toothpaste, and these lesions DO show a sharp delineation at the gingiva with a sloping finish in the coronal direction.
Not all persons with cervical lesions demonstrate occlusal wear, which would indicate a bruxing habit, and not all persons with severe bruxing occlusal wear exhibit cervical non carious lesions.
Frequently, the teeth in which there is ongoing erosion of buccal tooth structure have no opponent in the opposite arch. If it can be shown that the damage is ongoing, or that the damage began after the extraction of the opposing tooth, then bruxing cannot be a factor in producing it.
The theory of abfraction postulates that toothbrush abrasion works in combination with bruxing to create some fairly bizarre effects on teeth. The image below shows a tooth which has assumed the shape of a Coca Cola bottle. You are viewing the back of the tooth in a mirror. Click the image to enlarge it. The yellow arrow emphasizes the area of concern. On the enlarged image, you can see that the damage stops at the gum line, leaving a shelf of unaffected root about even with the level of the gums.
On the other hand, the fact that this tooth is the last in the arch makes it more vulnerable to abrasion by the toothpaste on toothbrush bristles, as it does not have another tooth behind it to “protect” it. Dentists who do not believe in the theory of abfraction argue that natural tooth structure is simply abraded away by overzealous tooth brushing. The image below shows a similar 270 degree lesion surrounding both central incisors. The lingual (tongue side) of the teeth are not affected as severely as the buccal (front) and interproximal (between the teeth) areas where vigorous brushing would most likely take place
Both of the images below represent the type of cervical erosions under discussion. Those dentists who subscribe to the theory of abfraction believe that patients with these lesions are probably severe bruxers as well as “severe tooth brushers”. Click on the images below to see enlargements.
For those who believe in the theory of abfraction and wish to read more about it (with numerous images), you should see the site of Dr. Brian Palmer, and click on the three sections of his long presentation.