Microbes That Bite Can Kill More Than a Smile!
Bacteria Can Be The Couriers Of Disease
By Steve Sternberg, April 14, 1998--USA TODAY
The obituaries said nationally known syndicated humorist Lewis Grizzard died of heart disease, but there may have been more to it than that.
At least one doctor who evaluated his case believes that Grizzard's heart valve problems stemmed from neglect of his teeth.
"He had bad teeth. He wouldn't floss, he wouldn't brush,'' says Atlanta oral surgeon Thomas Boc, who consulted on the case. "He was a classic example of somebody whose chronic dental infection led to chronic heart disease, valve failure and ultimately death.''
Grizzard, 47, died in March 1994. Such cases, though extreme, are anything but unique.
Doctors have known for years that dental infections pose a risk to heart valves, but new research suggests that dental infections also may be implicated in hardening of the arteries, heart attack, stroke and spontaneous, pre-term births.
The research indicates the buildup of oral bacteria won't just wreck your smile, give you bad breath and cost you your teeth. It may cause trouble "a mile away, somewhere else in the body,'' says Dennis Mangan of the National Institute of Dental Research (NIDR), Bethesda, Md.
If the eyes are a window into the soul, this theory holds, the mouth is a portal to the rest of you.
Some of the associations are firmer than others. But of this there is no doubt: Even the healthiest mouth is laden with bacteria, underscoring the need for good dental hygiene.
"The mouth is not a sterile environment,'' Mangan says.
That's putting it mildly. More than 200 types of bacteria dwell in the mouth. Of those, about 20 have been identified. The bacteria fall into two major groups, distinguished by their shapes. Some are like rods, others like balls.
A person with healthy gums needn't worry. A constant flood of saliva -- major glands in the mouth supply more than a quart a day -- flushes most of these germs down the hatch, into a cauldron of lethal digestive juices.
Saliva, the wonder drug!
If a drug company manufactured saliva, the marketing department might tout it as a wonder drug. For example, saliva carries proteins that stop many bacteria from sticking to teeth.
It also has proteins that cause bacteria to clump for easier disposal and buffers like bicarbonate to neutralize bacterial toxins. In a test tube, proteins in saliva can kill bacteria.
Doctors have found that the mouths of people whose glands can't make enough saliva become a frequent target of bacteria, viruses and fungi.
In most people, periodontal trouble begins with painless, symptom-free infections at or beneath the gumline.
Roughly half of all adults suffer the first stage of these infections, known as gingivitis, says Robert Genco, State University of New York, Buffalo. The percentage climbs with age. By age 60, 25% of people have advanced infections called periodontitis.
The danger zone lies in an area of the mouth known to dentists as the sulcus, which is the shallow trench where the teeth emerge from the gums.
Typically, trouble begins when ball shaped streptococci and other bacteria stick to the teeth. Streptococci use a glue, made from sugar, that is similar to the substance mussels use to cling to the pilings of a dock. Porphyromonas gingivitis bacteria uses tendrils known as fembria.
These different strains of bacteria are symbiotic, meaning that they live together in highly organized colonies. Fluid-filled channels between the colonies carry off antibiotics, making the bacteria up to 1,000-fold more antibiotic resistant than bacteria floating freely through the blood. This makes the colonies extremely tough to dislodge.
Bill Costerton of the Center for Biofilm Engineering at Montana State University, Bozeman, has witnessed this bacterial buildup cell by cell, on a tiny scale covering just a millionth of a millimeter.
Costerton uses an experimental technique, adapted from space-age technology, called a confocal scanning laser scope. This device, which does not harm the bacteria, bounces intersecting blades of photons off bacterial colonies. A $500,000 computer turns the reflected photons into a colored image.
"We can watch bacteria settle on the tooth surface,'' he says.
Streptococci settle first in a layer one or two cells deep; porphyromonas uses the strep for a foundation and builds towers 500 cells deep. "Strep will grow down the tooth, then porphyromonas widens the sulcus and makes it extremely pathogenic,'' Costerton says.
This is when the trouble really starts. The trench not only grows, but the body responds by activating the immune system, flooding the tissues with inflammatory substances known as cytokines.
A recent report in the New England Journal of Medicine linked one of these, C-reactive protein, with more extensive buildup of fatty deposits inside blood vessels.
Brent Muhlestein of the LDS Hospital, Salt Lake City, told the American College of Cardiology two weeks ago that antibiotics appeared to mute this inflammatory response. But the study, designed to determine whether antibiotics can reduce the risk of heart attacks, cardiovascular deaths and unexpected bypass operations, will not be complete for a year and a half.
In February, the University of Minnesota's Mark Herzberg reported, however, that the bacteria in dental plaque can cause heart-attack-inducing blood clots. In that study, the researchers injected rabbits with dental bacteria. Clots formed within minutes.
Genco, of Buffalo, says porphyromonas tends to clump with blood-clot producing cells called platelets.
Researchers believe that these clumps irritate blood vessel walls, leaving abrasions where fatty deposits may cling, narrowing the arteries. Blood clots, perhaps formed to repair the damage, may cause heart attacks, he says.
In a study of the Pima Indians, Phoenix -- a tribe plagued by a high rate of heart complications from diabetes -- Genco and his colleagues have found that those with gum infections have triple the heart attack risk as those who don't have gum infections. Genco calls the rate ``astonishing.'' Since few Pima smoke, he notes, cigarettes can't be blamed for the difference.
Not every study has produced positive results. William Christen of Brigham and Women's Hospital, Boston, says that researchers looked at whether gum disease influenced heart attack risk in 22,000 doctors participating in the long-term Physicians Health Study. It did not appear to, but the study was based on the doctors' own reports of gum disease.
A study of 44,119 male health workers, by a research team at Harvard's School of Dental Medicine, yielded similar results overall -- but the researchers did find a link between tooth loss and and the risk of coronary artery disease among men with a history of gum disease.
This suggests the importance of tooth loss as a measure of the severity of gum disease; this may be a more accurate marker than a doctor's memory.
Although all facts are not in yet, some dentists and oral surgeons say there's strong anecdotal evidence that dental infections play a role in heart disease.
"We've been seeing this for 20 years,'' Boc of Atlanta says. "It's been a very contentious issue between oral surgeons and cardiologists. We were often called to the operating room before bypass surgery to remove infected teeth. Almost to the patient, the ones who came in for heart surgery had an associated dental problem.''
Boc says cardiologists didn't appreciate the extent of the probable link between dental infections and heart disease. "It was like screaming at a brick wall. They didn't see an association. They couldn't see it. They weren't dentists, and there was nothing in the literature about it.''
Cardiologist Muhlestein, of Salt Lake City's LDS Hospital, says most of the reports have been in dental journals until recently. "I'm just finding out it's all there and getting into it. It sounds very interesting as a hypothetical explanation that might be real.''
Risk of pre-term birth?
The womb is even farther from the gum line than the heart, yet several studies have linked dental infections with spontaneous pre-term birth.
This research began in the mid-1970s.
Marjorie Jeffcoat of the University of Alabama, Birmingham, reasoned that -- since other infections have been shown to cause premature births of low-birth-weight babies -- dental infections may have a similar impact.
If they could, researchers thought, it would help explain the 25%-50% of premature births that are unexplained. It might also explain why so many more black women, who are often unable to gain access to dental care, have premature, low-birth-weight infants than white women.
She and her colleagues studied 120 women from rural parts of the state and found that women with dental infections were three times more likely to have premature, low-birth-weight infants.
Steven Offenbacher of the University of North Carolina and his colleagues did a similar study on 124 women but found a sevenfold increase in risk.
He and his team also gave hamsters low-grade skin infections, using an oral bacterium found in humans.
Sure enough, the researchers reported in 1994 that infected hamsters had more pre-term and smaller fetuses than uninfected ones.
These studies, though interesting, were inconclusive.
More studies under way!
Now Jeffcoat and her colleagues in Alabama -- including obstetricians -- plan to study 4,000 women, 1,000 of whom have already been recruited. These women will be examined while they're pregnant, and the outcome of each pregnancy will be recorded. About 400 of those with gum disease will be treated. Some will have their teeth cleaned, others will have a full-scale periodontal treatment with antibiotics.
"We want to see if we can cut down their risk,'' Jeffcoat says.
That remains an open question in each of the research fields described, says Mangan of NIDR. Researchers are still trying to determine whether there's a problem, and if so how extensive it is. "We're new at this,'' he says.
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