The Wonders of Saliva
By Rosie Mestel

It protects our teeth, fights infection and is sorely missed when absent. Scientists are fascinated by its medical potential.

Saliva is a humdrum liquid, the stuff of giggles, dribbles and schoolyard grossness. It's hardly something to take seriously--until, that is, you lack it. When your glands no longer pump out a normal and robust 2 to 3 pints daily, then you'll come to appreciate spit for the wondrous substance it is--one that does far more than render food slimy and digestible.

Saliva, science has revealed, is much more than water. It is packed with proteins that help control the teeming hordes of microbes in our mouths. It is stuffed with substances that make our spit stringy, stop our teeth from dissolving and help heal wounds. It is brimming with a plethora of hormones and other chemicals revealing anything from whether one smokes to whether one is stressed.

Thus it's no wonder that trouble starts brewing when mouths dry out. Cavities blossom like flowers in spring. Tongues become sore and fissured, and breeding grounds for yeast. In a spit-depleted world, speaking and swallowing are challenges, eating a cracker is the height of recklessness and you wake up with your tongue glued to your mouth. Such indignities will be more frequent in future years because the number of saliva-depleted people stands to rise, experts predict. Tens of thousands of Americans receive radiotherapy for head and neck cancers each year--a treatment that can permanently damage salivary glands. Maybe a million have dry mouths because their immune systems are attacking their own glands in a disease known as Sjogren's syndrome.

But an increasing number of people (25 million by some estimates, and more to come as the population ages) get dry mouths as a side effect of more than 400 of today's medications--taken for depression, high blood pressure and more.

A small band of scientists, including an Iranian researcher, Mahvash Navazesh of University of Southern California, is fighting back.

Armed with a deep knowledge of saliva gleaned over decades, this cadre--which jocularly refers to itself as the "salivation army"--is working to create better artificial salivas to keep mouths wet and protected and find new drugs to help saliva flow more freely. They're trying to repair salivary glands with gene therapy--even to build an artificial gland to implant in the mouth.

And their vision goes far beyond simply mending the mouth. Just as leech saliva gave us anticoagulants, researchers hope that our very own spit may yield new antimicrobial drugs to help battle germs. Or that sick people's salivary glands can one day be coaxed to make hormones that are needed for their bodies to heal.

Mrs. Navazesh, is associate professor and chairwoman for oral medicine and oral diagnosis at USC's school of dentistry. She holds up slide after slide depicting only too clearly what she means--raw tongues white with yeast, teeth brown or black with decay on their ridges as well as at or under the gumline, where decay is usually rare.

If only, she says, more dentists and doctors had saliva at least somewhat on their minds.

To Navazesh's mind, the first part of paying attention is measuring saliva flow properly so you know if there's a lack--and she is an expert at that, demonstrating her craft one morning on a well-dressed, middle-aged woman who has been referred to USC with a suspected saliva shortage.

At Navazesh's request, the patient sits in the dentist's chair, head tilted upward, eyes open, and drools into a tube for five minutes. Next she chews gum for five minutes in time with the click of a metronome--and spits into a second tube. Finally, she sucks a lemon candy (again in time with the metronome) and spits into tube No. 3.

The tubes are weighed--the first holding a dribble, the second an inch, the third nearly two--and saliva output calculated. Finally, the verdict is delivered: The patient's flow is on the low side and could indicate an early stage of Sjogren's syndrome.

Diagnosis is crucial, experts say, because there are things patients and dentists must do to fight rampant tooth decay. Stringent oral hygiene is key--brushing and flossing after every meal, daily application of fluoride gels, monthly tooth-cleaning appointments.

Drug companies continue to neglect the dry mouth arena, he says, because they don't see much money in it. And today's gland-stimulating drugs can only help people with glands left to stimulate.

Artificial salivas, unimpressively, have fared no better than tap water in most clinical trials.

Saliva science kicked off relatively late in the history of medicine, recounts Irwin Mandel, grand old man in saliva research and somewhat of a historian on salivary matters.

Centuries before Mandel got his hands wet in the lab, physicians thought the salivary glands were lowly excretory organs--ridding the body of toxins and evil spirits from the brain. They would dose patients with poisonous bichloride of mercury, causing saliva to pour from the mouth.

Even in the last century, scientists only got serious with saliva well after they'd tackled other bodily fluids like blood.

("Saliva doesn't have the drama of blood, it doesn't have the integrity of sweat, it doesn't have the emotional appeal of tears," says Mandel, a professor emeritus of Columbia University.)

But from the '50s onward, Mandel and a handful of others have established that human saliva is filled with hundreds of useful chemicals, floating around with millions of bacteria, viruses, yeast and skin cells in what Mandel terms a "chowder." They've been busily investigating such proteins--and finding that some are important for maintaining oral health.

"If saliva were water, we would have little stumps of teeth or no teeth at all by age 20--we would have dissolved our teeth away," says Frank Oppenheim, chairman of the department of periodontology and oral biology at Boston University.

(end)
Condensed from Los Angeles Times, Jan 21, 2002
© 2002 - Khorsheed.com - Feb 2002