Why Do Some People Never Get Cavities?

Cavities are an infectious disease. When we think of diseases, we think of viruses like COVID, bacterial infections and cellular dysfunctions like cancer. Fortunately, cavities are preventable with reasonable practices, unlike some of the other diseases which are either extremely hard to eliminate or not yet treatable. Dental science has made cavities a thing of the past for some people, but unfortunately for others, cavities can destroy teeth and require implants or dentures as a substitute.

What are the facts about cavities?

The structure of the tooth is an interesting design. There is a hard shell made up of acid resistant material called enamel. This looks like some natural rock formations with rods surrounded by a matrix that holds the rods together. Under the enamel is a softer material called dentin. The structure of enamel and dentin works to absorb stresses many times stronger than dentin on enamel alone, like corrugated paper in cardboard packing boxes. A single sheet of paper cannot hold a washing machine, but when folded in a specific manner, the weight bearing capacity of paper is magnified many times over.

So, the tooth is composed of two layers of the hardest material in the body, but it is not impervious to the slowly dissolving force of acid.

Where does the acid come from? We all grow bacteria everywhere outside and inside our bodies. Some of the bacteria is vital to our survival, such as the gut bacteria that help with digestion. The acid in the digestive tract is made by the bacteria that inhabit different zones. In the mouth, the acid is produced by Streptococcus Mutans. When we eat, especially when we have a high sugar diet, there are enough lingering food substances including sugar that cause the remaining bacterial populations to virtually explode in density. As the bacterial colonies grow, they ingest the sugar like substances that remain in the mouth and on the teeth, and in return they produce chemicals that have a poor odor (like mercaptans that we recognize as bad breath). They also produce destructive quantities of acid.

Bacteria produce substances like dextran that hold them tightly to the teeth, so they cling and do not wash away. A they cluster around the teeth in colonies, the acids they excrete hug the enamel surface and ever so gradually etch and then perforate the enamel to produce the smallest variety of cavities. At first these small holes can remineralize with the calcium found in saliva or the fluoride found in toothpaste. As the cavities get larger, however, they penetrate the enamel and then spread more quickly inside the dentin, which is much weaker and less resistant to acid.

When these larger holes are spotted by the dentist using visual means or x rays, the treatment to stop the cavity or decay can be started with fillings, or crowns. When the cavity is left to progress indefinitely, eventually the tooth must be extracted and replaced.

Through science, dentists have found that the specific bacteria that produce acid (Strep Mutans) can be reduced in quantity, so that there is less acid produced. This is done with mechanical means such as tooth brushing, flossing and water pick to remove food particles. Some fortunate people inherit oral bacteria that do not include destructive Strep Mutans. For others not so fortunate, scientists have found that replacing the “bad” bacteria with” better” bacteria can be done with the use of oral probiotics. When the “bad” bacteria are replaced, there is less acid production and therefore less likelihood of cavity production.

Although there are some cases where there are defects in the enamel due to malformation during development from internal or external sources such as drugs or high fevers, in most cases, cavities are preventable, the rate of decay can be slowed or prevented, and thankfully the destructive result of cavities can be treated painlessly and indefinitely.