Teeth are a mineralized structure made primarily from calcium. Because of this, they can be dissolved readily by acid. When this acid comes from bacteria, decay occurs. However there are other sources which can also provide enough acid to damage the teeth.
One common source of acid is the hydrochloric acid found in the stomach. Any time stomach contents are in the mouth, acid can cause erosion of the teeth. This becomes a potential problem for persons with bulimia, (habitual vomitting) gastric reflux esophogitis (GERD) or hiatal hernia (medical conditions which allow stomach contents to seep into the mouth when lying down).
Erosion of the teeth can easily be distinguished from wear of the teeth by clenching or bruxing. The following images describe characteristics of erosion.
Erosion of maxillary lingual surfaces
The side of the upper (maxillary) teeth facing the tongue (known as the lingual surface) usually has the greatest amount of erosion (arrows). The yellow portions in the center of the teeth are the areas where the enamel (the hard outer layer of the teeth) has been disolved and worn away. The portion of the tooth thereby exposed is the softer dentin which is even more prone to erosion by acid and wear from chewing and clenching.
Erosion of mandibular buccal surfaces.
The side of the lower (mandibular) teeth facing the cheek (known as the buccal surface) is also prone to erosion from acid from stomach contents. Notice how the lower teeth seem to slant toward the tongue due to the loss of tooth structure toward the chewing surface of the teeth. Both the upper and lower teeth are reduced in height to about half of their normal length. These patterns of erosion on the upper and lower teeth occurs because of where the acid tends to pool in the mouth. Also notice the shortness of the posterior (back) teeth. When the erosion is severe enough that the enamel of the chewing surfaces is lost, the softer portion of the tooth (dentin later) is exposed and wears rapidly. Since the teeth are shorter the jaws close further before the teeth contact. This condition is called a "closed bite" resulting in a loss of the vertical height of the face, wrinkles in the skin at the corners of the mouth and can sometimes cause soreness of the facial muscles or headaches.
Since most filling materials are more resistant to dissolution by acid than the teeth, it is common to find that parts of the tooth have dissolved away leaving the filling at its original height. This gives the appearance that the filling is "raised" (arrows) while in fact, the true cause is the height of the tooth is lowered. This is a classic finding in erosion cases where the fillings have been present for a long time. When teeth are shortened due to wear of the teeth by clenching or bruxing the fillings are worn to the same level as the surface of the tooth and do not appear raised.
Click here for additional images of bulimia examples
Click here for additional information about the treatment of erosion and resulting wear.
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