What is a cavity anyway?

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Most everyone reading this column is probably aware that a cavity is the layman’s term for a hole in a tooth. In dentistry we call it caries. Most everyone would agree that a cavity is a good thing to avoid, and if not possible to avoid, to have fixed, so that further damage to the tooth doesn’t occur. But what exactly is this hole, and how did it happen?

The tooth has multiple layers, the outermost being enamel, the hardest surface in the body, harder even than bone. It is 96 percent inorganic, mostly made up of minerals, chiefly calcium, phosphorus and fluoride. Once the tooth is formed, enamel is not a renewable tissue. It cannot regenerate like soft tissue when injured. Because of this, dental professionals encourage patients to use home care techniques and products that preserve the enamel. Though very hard, it is not indestructible.

Many people believe that sugar causes cavities. Though certainly a part of the process, sugar is not directly the cause of caries. Bacteria are the real culprits. Bacteria are always present in the mouth. Brushing, flossing and rinsing are recommended ways to keep the numbers of bacteria to a minimum. 

When we consume food, especially easy to digest sugars and simple carbohydrates, the bacteria feast too. The by-product of their feast is acid. Acid starts to demineralize, or dissolve, the hard, inorganic enamel structure. Normal body pH (acidity level) is 7.4 (just on the alkaline side of neutral). When the pH drops to 4.5-5.0 in the saliva, the minerals start to dissolve out of the tooth. If fluoride was present when the tooth formed, the pH level at which the destruction starts to occur is lower, thus the reason dental professionals favor fluoridated community water and fluoride supplements in childhood. 

It takes the body about half an hour to buffer saliva back to a neutral level. Minerals stay present in a dissolved form in the saliva, and can be taken up by the enamel again. This back and forth process, called demineralization-remineralization, is happening continuously in the mouth. A cavity occurs when the demineralization process outpaces the remineralization process. 

One of the first clinical signs a cavity is forming is called a white spot lesion. The loss of minerals to the enamel causes it to take on a chalky, white appearance. At this stage, the enamel may remineralize and a cavity may never form. But if bacteria are not removed regularly, if sugar is eaten frequently, and if salivary flow is diminished, a cavity is likely to result. Once the cavity breaks through the enamel surface, it can no longer remineralize, and will worsen with time. 

At this point, it may not hurt much, and can be pretty easily restored by your dentist. If it isn’t restored, the process continues, causing a larger hole, eventually breaking through to the dentin layer, which is less hard than enamel, and continuing to the pulp. Once the pulp is involved, the tooth becomes painful, may abscess and requires a root canal procedure to restore.

The moral of this story: Daily remove as many bacteria from your mouth as possible using approved methods and products, keep snacking to a minimum (low frequency), and visit your dental hygienist and dentist regularly to detect and restore early cavities.


Janine Sasse-Englert is the director of the Sheridan College Dental Hygiene Department.


By |Jun. 2, 2017|

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