NONCARIOUS CERVICAL LESIONS IN ADULTS

Most adults eventually get ditches or worn areas right above the gumline primarily on the upper teeth adjacent to the cheeks. The most frequently involved teeth are the upper canines, bicuspids and first molars. These defects are not the result of dental caries (cavities) but of multi-factorial consequences brought about by abrasion (loss of tooth structure due to mechanical wearing, e.g. toothbrushing), erosion (dietary causes due to chemial dissolution especially by acids the most damaging being soft drinks, frequent vomiting) and attrition (wear from contact with other teeth). Sometimes these worn areas become so deep that the nerve becomes involved or the tooth breaks. Researchers have always thought that the most damaging of these factors was toothbrushing but wedge-shaped lesions have been found in animals teeth (cats and horses), artificial teeth in dentures, teeth of pre-historical people and chemically inert materials such as gold. This would lead us to believe that this is a complex process that probably involves all three of the above causes and, perhaps, other factors that are not so obvious. (My cats don't brush that often and are not allowed to regularly drink Pepsis). By the way, these "ditches" in teeth are called abfractions.

Before an abfraction can begin, there has to be gum recession on the cheek side of the involved teeth. The degree of this recession is an individual process which is influenced by the quality and quantity of the gum tissue (a genetic property), the position of the teeth in the arch (the canine and premolars have the thinnest tissues) and whether or not a person has or has had treatment for periodontal (gum) disease. Once the gum has receded, the degree of damage to the tooth itself is influenced by how much of the tooth root is exposed to the environment. The root and the inner layer of the crown of a tooth are both made out of the same living substance called "dentin". Whereas the crown of a tooth (the part above the gumline) has an outer, protective, mineral layer of enamel which is the hardest of human tissues, the dentin of the root only has a thin cover of living cells (called "cementum") which is easily worn away. The enamel thins out and ends as it meets the cementum at what is called the "cemento-enamel" junction (called the "CEJ"). Once the gum tissue recedes past this junction, the process of abfraction can accelerate.

With all of this in mind, there is another potential risk factor at work. When we chew and when we grit and clench our teeth in response to stress (called brusixm), teeth can flex. This constant flexing, over time, introduces lateral forces upon the tooth which acts as a lever whose fulcrum is located at the bone crest which is adjacent to the CEJ. The resulting tensile stresses are concentrated in this area causing a breaking of the chemical bond between the thin enamel and dentin crystalline structures exposing more of the soft dentin at the gumline which contributes to a hastening of the abfraction process. There is a very significant correlation between teeth with abfractions and the presence of wear facets that appear on the biting surfaces of these same teeth. These worn, or flattened areas, are diagnostic for teeth that have been subjected to abnormal, or lateral, biting stresses from opposing teeth; sometimes we see teeth as flat as a tabletops!

It is often wise to restore these areas with some sort of white filling material. This will slow down the abrasive effects of over-brushing and also the erosive effects of chemicals on this area. And, a strong resing filling will help reduce the flexing by adding bulk to the body of the tooth. And, since most of the clenching and grinding that we do is during sleep, this process can be greatly reduced by wearing some sort of a night guard over the teeth in either arch at night.