What’s a cavity?

I think most adults and probably a lot of kids only kind of know what a dental cavity is, and I think many dentists assume everyone does. Unfortunately, when I made a casual survey of my friends and family I got a whole array of responses, some pretty accurate and some fairly funny. Although dental cavities are not the most common of diseases in the human mouth they’re the most obvious to us all.

So what do most people think of as a cavity? I imagine pictures and impressions of black spots, teeth “rotten away”, and pain come to mind. As humans, we usually visualize terms or ideas as still-framed snapshots instead of processes that occur over time. For example when asked to create a mental image of age, we usually picture either a baby or an old man. We rarely picture the baby aging into the old man. Most people’s mental picture of cavities are the same, but cavities are really a process that occurs over time.

First let me digress and give a little history lesson. Many people may have wondered, “Tooth brushes and tooth paste are relatively new inventions, so how did the cavemen care for their teeth or prevent from getting cavities?” In fact, we tend to imagine cavemen as having ugly, rotten teeth, but the archaeological evidence states otherwise. Most skeletons of ancient human beings have impeccable teeth without cavities. So what did they brush their teeth with and why don’t we just do the same, right? The answer is not necessarily in how they cared for their teeth but rather a much broader aspect of ancient life. Lets fast forward to late 19th century London. Although, as Americans, we stereotype Merry ol’ England as a nation of bad teeth, England has the oldest and most in depth surveys concerning their teeth than any other nation. And when this mountain of data was examined to see how rampant cavities are and were, some interesting facts appeared. Interestingly, their was a gigantic increase in the incidence of cavities in the city of London during the late 19th century. Oddly, this coincided with the increased use of the modern toothbrush. Now the common mistake would be to blame the toothbrush for cavities, but it makes more sense to say the use of toothbrushes were in response to the increase in cavities. So anthropologists and dentists looked at other possible reasons for the increase, and one historical event stood out by mirroring the increase in cavities. This event was the Industrial Revolution that occurred at the same time in London.

Now how did something like the advent of the assembly line, factories, and the locomotive affect teeth? The answer can be found by simply asking a child today, “What causes cavities?” Sugar. Now we think of sugar today as the little, white crystals we put in our morning coffee, but this kind of sugar, or refined sugar, was not around before the Industrial Revolution. It’s called refined because it has been purified and concentrated. Have you ever tried to use that “natural” or “raw” sugar to sweeten your tea before? Notice how it takes a whole lot more of that “raw” sugar to sweeten it the way you like, but only half as much of the white, “regular” sugar will do the trick? Well the “regular” or white sugar has been refined. The modern era not only brought us refined sugar, but also gave us the super-duper sugar we all love, high-fructose corn syrup. To complicate it even more, we need to include items high in starch as sugars as well. Our favorite snacks like potato chips, french fries, and breads are all high in starch. Its worthwhile to note that the process of converting starches into sugars begin in our mouths due to our own saliva. So the Industrial Revolution brought us all the goodies of modern life but also gave us the modern diet which is high in refined sugars and starchy foods, and those lil’ bugs in our mouths can’t thank us enough for it.

Lil’ bugs in our mouth? Distasteful as it sounds, but yes we all have bacteria that live in our mouths no matter how many times we rinse with mouthwash or brush our teeth. Now these bacteria are not bad for us. In fact science has shown many of them are extremely beneficial. But remember the advise our moms gave us growing up about, “everything in moderation?” The same is true for bacteria. Too much of anything is gonna be bad for you. Now these bacteria are able to live in your mouth because like you, they live off the food you’re eating. Bet you didn’t think you were sharing every meal right?

Well this brings us back to the Industrial Revolution and those refined sugars and starchy foods. Ever had a power bar? Those meal replacement bars supposedly have the nutritional needs of an entire meal in a single bar. Well high-fructose corn syrup is the power bar for the bacteria that live in your mouth. It’s like a never ending buffet of energy for them and they begin to multiply faster and grow faster.

So lets make this discussion even more distasteful. Specific bacteria in your mouth cause cavities, and these specific bacteria love sugar. The “how they cause cavities” is the distasteful part. Just like you and me, when bacteria eat more they… well, they create more waste products is the nice way to say it. It’s the acidity of these waste products that starts cavities and makes cavities get larger.

To top it all off, sugars are sticky as you probably already know. The inherent “stickiness” of sugars also allow these bacteria that cause cavities to stay on your teeth. Interestingly, your teeth are designed to “wash” themselves with the saliva in your mouth. Your teeth are so smooth that bacteria can’t “stick” to them normally. Your saliva normally washes these harmful bacteria away from your teeth through out the day. Remember the question about why cavemen didn’t get cavities? Here’s the answer. Without sticky, refined sugars, cavemen teeth were washing themselves of harmful bacteria naturally, without the need for a toothbrush.

So the process of a cavity (the accurate dental term is caries or carious lesion) is this…

1. Refined sugar sticks to your teeth and is not brushed off with a toothbrush.
2. Cavity causing bacteria get stuck to the refined sugar on your teeth as well
3. These bacteria rapidly multiply and grow because they have a high energy food source and a place to live, safe from the self-cleaning action of your saliva.
4. Their waste products accumulate around them on the surfaces of your teeth.
5. The acidity of these waste products weakens your natural tooth structure.
6. The process repeats until a cavity is formed and it grows until the bacteria are removed.

So that’s basically what a cavity is. It can be thought of as the process of melting away tooth structure by the acids created by bacteria.

The next step is the treatment of cavities by a dental professional, but that’s for next time.