(CNN) -- Remember "The Big Book of British Smiles" from "The Simpsons"?
The dentist used it to scare children into proper dental hygiene.
And let's be honest, it was funny! Because though British tea and good manners have an excellent international reputation, British teeth are mostly used as a punch line.
But tooth decay is far from only a British problem -- in fact, it's one of the most common chronic disease worldwide.
Scientists say the health of your teeth depends on a combination of genetics and dental hygiene. We all know that person who never brushes, eats tons of candy and rarely (if ever) has a cavity. Then there are those of us who floss regularly, yet still end up breathing in the laughing gas once or twice a year.
About 60% of the risk for tooth decay appears to be due to genetic factors, says Mary L. Marazita, director of the Center for Craniofacial and Dental Genetics at the University of Pittsburgh School of Dental Medicine.
Though genetic dentistry is still in its infancy, scientists have identified five areas where genes play a role in tooth decay:
Everyone likes sweets right? Well sort of, said Marazita. Though you may believe all children turn into crack-addled lunatics at the sight of the drugstore candy aisle, scientists have identified gene variants that show a range of "sweet preference." All other factors being equal, the stronger your genetic "sweet preference," the more likely you are to develop tooth decay.
So, two children raised in identical environments may have completely different attitudes to sugar: from "I'm just not that into candy" to "Mom caught me licking the stray candy chips from the grocery store gum ball machine. Again."
Marazita couldn't tell us exactly where to find these kids who are "just not that into candy," but said, "just because they're not hanging out at your house doesn't mean they don't exist."
This one is a no-brainer. Some people have softer tooth enamel than others. The softer the enamel, the easier it is for bacteria to do their excavation, leading to cavities. Because genes are the primary determinant of enamel structure, they have a big effect on whether you get tooth decay.
Cilantro, an herb common in Asian and Latin American cooking, is the perfect topping for fresh fish tacos -- at least to some people. Others would just as soon go home and lick a bar of soap.
That was the finding of a recent study that identified a gene variant for the ability to enjoy cilantro. "It tastes like soap" was the most common refrain among those missing the gene variant.
"Taste ability" is a measure of the variety of things you can taste -- not simply whether you are genetically predisposed to enjoy certain flavors (as in the cilantro example), but also whether you are able to perceive certain flavors. This is a complex process that includes your tongue and is inextricably linked to your sense of smell.
Studies show the greater the variety in your genetic taste ability profile, the less likely you are to develop tooth decay. Whether that's because more variety leads to fewer sweets, or whether there are other reasons, is not yet clear, but scientists are continuing to study the connection.
Calcium, potassium and other elements are important for strong healthy teeth that resist tooth decay. But it's not as simple as eating the right foods; these elements must be properly metabolized to be useful.
Your saliva plays a big part in this process, and scientists have identified gene variants that make some people better at it than others.
There's a whole field of study called microbial ecology that looks at the various communities of bacteria that live in the human body. Yeah, that's right, communities -- plural.
In your mouth alone there are separate communities of bacteria on your tongue, on the surface of your teeth and below your gum line. Together, these communities make up what is known as your microbiome.
Don't worry, it's all perfectly normal. But your body's immune response to these communities affects, among other things, your risk of developing tooth decay.
What about the other 40%?
"So," you are probably asking yourself, "if my genes are 60% of my cavities, what governs the other 40%?"
Answer: Soft drinks and fluoride.
OK, that might be a slight exaggeration. The other 40% has to do with environment: diet, brushing frequency, smoking habits, dental care access, culture, even socioeconomic factors, according to Robert J. Weyant, chairman of the University of Pittsburgh's Department of Dental Public Health.
But so far, the single biggest environmental factor scientists have identified that encourages tooth decay is the consumption of sugary drinks, Weyant said. Any sugary treat can hurt, but sugary drinks are particularly adept at spreading sugar to every corner of your mouth to feed the bacteria that cause decay.
Tea and coffee don't even rate in comparison. Alcohol is not even on the list. In fact there is very little to suggest that alcoholic drinks have any significant effect on tooth decay -- unless, of course, you like to drink your whiskey in a large glass of soda.
On the opposite side, the single biggest environmental factor known to protect against tooth decay is fluoride. Get it in your city water supply, get it in your toothpaste, get it in periodic treatments from your dentist, but get it somewhere. That is the consensus among dentists and public health experts alike, Weyant said.