Farmers, cowboys, and other sensible men always examine a horse’s mouth before buying it. One good look can sum up the horse’s health history and even predict how long the old boy will live. A human mouth isn’t much different. Just look at John Elway.

“This horse test is based on the old ‘focal-infection theory’, which says that an oral infection affects the whole body,” says Raul G. Caffesse, D.D.S., of the University of Texas-Houston Health Science Center. It was the cause for lots of tooth pulling until the dentists abandoned the theory 40 years ago.

But the focal-infection theory is making a big comeback (minus the fun of the extractions). And now it’s supported by more than frontier hunches. In fact, there’s growing clinical evidence that small infections in your kisser may be a contributing factor to several diseases. Although the theories are still controversial, dentists and other physicians think that the following five afflictions may be related to your mouth. That makes five excellent reasons to buy some floss – now.

Heart Attacks

Robert J. Genco, D.D.S., Ph.D., of the University of Buffalo, studied 1,372 people at the Cila River Indian community in Arizona and found that those with gum disease had triple the risk of heart attacks over a 10-year period. He believes that oral bacteria (there are 350 different types in your mouth) enter your bloodstream through small tears in your gums. The bacteria, Dr. Genco suggests, may infect your liver and cause it to produce artery-clogging proteins, or they may directly infect your heart arteries and somehow cause blockages. The exact mode of attack is still a mystery, he says, but Porphyromonas gingivalis bacteria have been found in fatty arterial blockages that cause heart failure.

You’ve probably heard that oral bacteria can be especially dangerous to people who have heart disease. If you have an ailment involving the heart valves, such as mitral valve prolapse or a heart murmur, you may need to take antibiotics before receiving dental treatment, says Mark V. Thomas, D.M.D., of the University of Kentucky College of dentistry. Dental work dislodges bacteria and nicks your gums, sending a rush of germs into your bloodstream. That can cause bacterial endocarditis, an often fatal infection that strikes about 20,000 people each year.

Strokes

Men with gum disease could be destined for drooling. University of Buffalo researches surveyed the health histories of 9, 982 people from 25 to 75 and found that the 35 percent with severe gum disease were twice as likely to have had a stroke. Oral bacteria may cause fatty accumulations in the carotid arteries in your neck, causing blockages, says John Marler, M.D., of the National Institute of Neurological Disorders and Stroke. These little logjams in your brain break apart, float upstream, and lodge in your brain. And if a tiny chunk dams up a blood vessel, your dancing days are over.

Diabetes

When a diabetic is fighting a bacteria infection, insulin works less efficiently. That can raise his blood-sugar level, says Perry R. Klokkevold, D.D.S., of the UCLA School of dentistry. If you’re battling diabetes—and about one in 17 Americans is—a gum infections can make managing the disease much tougher. When University of Buffalo researchers examined 168 diabetics, they found that those with periodontitis (severe gum disease) had the most trouble controlling their blood-sugar levels. That’s what eventually causes the kidney disease, heart disease, and blindness that plague diabetics.

Gum disease probably doesn’t directly cause diabetes, says Dr. Klokkevold. “This is a relatively new field of research, but we know that having gum disease will worsen diabetes,” says Christopher Saudek, M.D., a diabetes specialist at Johns Hopkins University in Maryland. “People with diabetes should be careful to keep their gums healthy.” And if you have both a gum infection and a family history of diabetes, get checked for diabetes immediately.

Ulcers

This point is still controversial, but some evidence suggests that the Helicobacter pylori Bacterium, which can cause stomach ulcers, resides in dental plaque, says Sherie Dowsett, D.D.S., of the Indiana University school of dentistry. She and her colleagues found that among 242 study subjects, 210 of them carried the bacteria in their mouths. IL Pylo may migrate down to your stomach and proceed to eat painful little holes, which is why we think every bottle of Pepto-Bismol should come with a free toothbrush.

Pneumonia

With every breath, your lungs suck down a stew of bacteria, including Chlamydia pneumonide and Pseudomonas aeruginosa, two bugs that cause respiratory diseases. Careful readers will have guessed one source: the plaque buildup around your teeth. Your immune system usually destroys these invaders. But when your resistance is low, such as during an illness or after surgery, they can infect your lungs and cause bacterial pneumonia, says Dr. Caffesse. This infection kills about 83,000 people a year.

“Get your teeth cleaned before you have surgery,” he advises. The day before surgery is best, but a week before is still helpful. And bug your parents to floss daily and visit the dentist every 6 months; they’re much more vulnerable to pneumonia than you are, young man.

MOUTH MAINTENANCE

Floss and Scrape, or Die!
Avoid gum disease, premature death, and cruel comparisons to Gabby Hayes

Your gums don’t bleed when you brush? They’re not inflamed or receding? Not painful to the touch? Great. But you still may have gum diseases. That’s because periodontitis (and advanced form of a gum disease) often shows no symptoms. So let a dentist probe your pie-hole every 6 months as if your life depended on it, because it does. And follow the five tips below. They’ll help ensure that you won’t bite the dust with plastic teeth.

• Don’t be half assed about flossing. “Flossing is 10 times more important than brushing,” says Steven T. Bunn, D.D.S., a dentist in Alexandria, Virginia. The broad, flat surface of your teeth harbor few bacteria, but the unbrushable crevices between teeth are loaded with garbage. If you won’t floss after every meal, at least do it once a day. But do it.

• Scrape, fool, scrape! Your tongue holds more bacteria than the floor of the men’s room at Grand Central Station. “If you don’t scrape your tongue after you brush your teeth, bacteria will instantly reinfest your mouth,” says Perry R. Klokkevold, D.D.S. Buy a tongue scraper at the drugstore and take a few good swipes every morning and night. “Brushing your tongue isn’t nearly as effective,” he says.

• Go dry. Brush your tongue isn’t nearly with a dry toothbrush once a day, advises Dr. Bunn. Research has shown that people who dry-brush have significantly less tartar buildup that people who brush with toothpaste. Use gentle side-to-side strokes in which the brush is half on the gums and half on the tooth.

• Prod yourself. Gum disease usually starts beneath the gum line, where brushing and flossing can’t reach. So use a “rubber-tip stimulator” says Dr. Klokkevold. After you floss and brush, trace the rubber tip beneath the gum line of every tooth. “Your gums may bleed and be a bit tender for the first few days,” Dr. Klokkevold says, but they they’ll toughen up and you’ll have destroyed whole nations of plaque.