Friday, January 25, 2013
What causes tooth decay?
Seems like a simple enough question. Sweet foods feed bacteria, which make acid, which burns a hole in the tooth.
But why do some very conscientious people still get cavities while a few lucky people seldom brush and never floss but don’t develop decay?
Since the 1950s the predominant theory about what causes tooth decay has been the so-called “Acid Theory.” This theory, as the name suggests, states that the acid level of the foods, liquids and bacteria that bathe the teeth are responsible for the majority of problems people have trying to keep their teeth decay-free.
Another model holds that the health of the body and the nutritional quality of foods eaten has an effect on the teeth’s ability to withstand insults. This school of thought answers to important sounding names such as the Systemic theory of Caries Development and Dentinal Fluid Transport Theory. Don’t let the big titles scare you off.
In case you are interested in some relaxing reading, Dr. Clyde Roggenkamp has assembled a book of more than 100 scientific studies he labeled Dentinal Fluid Transport based on near 40 years of research by endocrinologist Dr. Leonora and dentist Dr. Ralph Steinman from Loma Linda University. Their research turned up some fascinating results, and not just for dentists.
But first some basic groundwork is needed to understand their research. Teeth have three layers: a hard outer layer called enamel made of a latticework of minerals; a hollow center where the nerve and blood vessels run; and a slightly spongier middle layer called dentin, made up of hollow tubes that look like a honeycomb. These tubes transport moisture and nutrients from the middle of the tooth out to the enamel and the edge of the roots.
In their research, Dr. Steinman and Dr. Leonora injected radioactive dye in study participant’s stomachs and watched to see where it would go. They traced the dye from the stomach into the teeth, timing the trip at about 6 minutes. In healthy rats, fluid and nutrients flow up the root of the tooth and out through the tiny dentin tubes and across the enamel, causing the tooth to “perspire” or sweat, much like a maple tree in summer.
The journey from stomach to outer layer of enamel takes about an hour. Leonora and Steinman surmised that this positive pressure gradient or “perspiration” has a self cleansing effect, essentially buffering acid and rinsing bacteria off the enamel surface. Notice I said in healthy rats. This is where it gets really interesting.
Rats given a sugary snack at the same time as the tracer dye showed a curious reversal of the direction that fluid flows in the tooth. The elevated sugar levels caused the tooth to suck in rat sludge in the form of bacteria and acid from the enamel surface. This, as you may have guessed, resulted in the rats getting cavities. What was going on here?
Through their research, they discovered a hormone associated with the parotid gland. That’s the gland in your cheeks that squirts saliva at the thought of lemons.
The quantity of parotid hormone determines which direction fluid flows through teeth. High levels, perspiring teeth. Low levels, incoming sludge. Most curious, this hormone appears to be very sensitive to levels of simple sugars in the diet. High sugar consumption resulted in decreased levels of this critical hormone and the rats ended up getting cavities.
Perhaps the most intriguing of their experiments is one which demonstrated that rodents eating healthy rat chow but injected with sugars directly into their stomachs still got cavities. This demonstrated that, at least in rats, food and bacteria in the mouth might not be the only cause of decay. To the best of my knowledge, this experiment has never been replicated in humans.
What lessons can be learned from these experiments?
Proper nutrition is essential to healthy teeth, both inside and out.
Sugar, white flour and perhaps a diet low in trace minerals reverse fluid flow through teeth.
Altered saliva flow from medications or hormones decrease the tooth’s ability to protect itself from decay.
Stress doubles a rat’s chance of developing cavities. Presumably the amount of parotid hormone plummets.
Rats have a tough life.
Things that will help reduce decay for prone individuals:
Keep the teeth spotlessly clean with electric toothbrush, floss etc.
Eliminate simple sugars, and white flour products from the diet.
Fluoride application trays for home use.
pH-increasing mouthwash such as CariFree Rinse.
Xylitol gum, mints or lozenges.
Things that may help, although research is slim:
Antioxidants — Green tea is very high in antioxidants and has been shown in some studies to have a positive effect in reducing cavities. Caution: it contains 30-50 mg of caffeine per cup.
Vitamins D3 and K2 — Very thin research shows beneficial effect against tooth decay from taking these two vitamins.
I don’t think either the “Acid Theory” of tooth decay or the “Dentinal Fluid Transport Theory” on their own fully explain what hygienists and dentists observe on a daily basis about tooth decay.
We always observe decay starting where plaque is left on teeth. How fast it progresses into the tooth, however, may well depend on one’s diet. The importance of good nutrition cannot be overstated.
Dr. Eric Gustavsen practices dentistry at Southpoint Dental Center, 1129 S. Second Ave. More information on his practice can be found at www.southpointdentalcenter.com.