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Tooth Decay
What is tooth decay?
In short, tooth decay is a location on a tooth where so much of the tooth's mineral content as been dissolved away that a defect (a hole or a "cavity") has developed.
Now, let's back up a few steps and start a discussion about tooth decay so this blurb of a description makes more sense.
Tooth anatomy as it relates to tooth decay.
First off, you need to think of a tooth in terms of being a hard calcified object. Yes, teeth do have nerves in their centers and this tissue is soft, but the surface of a tooth (where tooth decay begins) is formed from types of tissues that are very high in mineral content. These tissues are called enamel and dentin. Our mock up of a dental x-ray shown to the right illustrates where the dentin and enamel aspects of a tooth are located
Enamel
The vast majority of the surface portion of a tooth that is visible is covered by enamel. You've probably heard that tooth enamel is the hardest tissue found in the human body. This is true. Enamel is over 95% mineral in composition. Most of this mineral is a compound called hydroxyapatite which, as you probably already know, has a high calcium content.
Dentin
You may be surprised to learn that teeth are not solid enamel. Only the portion of a tooth nature intended to lie at and above the gum line is covered by enamel. The bulk of a tooth, both its root and inner aspects, is composed of another calcified material called dentin. Dentin also contains the mineral hydroxyapatite, but to a lesser degree than enamel. Only about two thirds of the content of dentin is mineral so, relatively speaking, dentin is "softer" than enamel.
How does tooth decay form?
If tooth decay is a location on a tooth where its mineral content has been dissolved away and a hole has formed (a process called demineralization), how does this action occur? The answer is, the demineralization of a tooth is caused by acids, acids that are created by certain types of bacteria that live in our mouths.
Bacteria are living organisms just like we are. As you know, humans consume food and produce waste products that are subsequently excreted. Bacteria do the same thing. The bacteria that are capable of causing cavities (mutans streptococci and lactobacilli) consume sugars as food (glucose, sucrose, fructose, lactose, or cooked starches). The waste products these bacteria create from having consumed these sugars are the acids (especially lactic acid) which cause a tooth's demineralization (tooth decay formation).
The bacteria that live in our mouths eat when we do. So, as we ingest foods which contain sugars (such as soda, candy, milk, and even fruits and vegetables or the juices made from them) the bacteria get a meal too, and within minutes they start producing the acids which cause tooth decay.
What role does fluoride play in the prevention of tooth decay?
You've probably heard that fluoride is a good thing for teeth. In truth, fluoride, in moderation, is a very good thing for teeth, for people of all ages.
An exposure to fluoride (such as that contained in toothpastes and municipal water supplies) is probably the most effective anti-cavity treatment available today. Dental researchers have shown that just introducing fluoride into a (previously unfluoridated) city's drinking water supply can reduce its inhabitants' rate of tooth decay between 40 and 70 percent. Those are giant numbers.
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