BODY WATCH : Brush Up on Flossing : Your mother did her job, hounding you mercilessly to brush your teeth. Who’s nagging now? Your dentist, whose mantra is ‘Floss. Floss. Floss.’ Here’s the skinny.

Flossing removes plaque that hides between teeth and under the gum line--places toothbrushes can’t reach.

* Fond of your teeth and gums? Not flossing is a major cause of adult gum disease and tooth loss.

* Last year Americans bought 3.8 billion yards of floss, enough to wrap around the globe 86.7 times. Still, more than 80% of flossers don’t floss regularly, nor do they floss all teeth.

* Dental floss dates to the ancient Egyptians, who used sewing thread to clean between their teeth.

* The first commercial flosses--made of waxed and unwaxed silk--were sold by Johnson & Johnson in 1898.

* Because silk wasn’t widely available during World War II, floss use was limited until 1945, when manufacturers switched to nylon and other synthetics.

* Floss innovations during the ‘70s and ‘80s included extra fine, mint waxed and unwaxed, cinnamon, bubble gum and mint with baking soda for that fresh feeling.

* Twists of the ‘90s include neon colors, flosses made of the same material as Teflon and flosses with fluoride.

* Today more than 50 companies sell hundreds of flosses with catchy monikers like Easy Slide, Glide, the Way It Was and Sweet Breath.

* There is no added health advantage to using flavored, waxed, fluoride-covered or baking soda-coated dental floss.

* Certain floss types may be best for particular mouths. If you have larger spaces between your teeth, use a thicker floss. If you have restorations, try a waxed floss--it’s less likely to shred. If you have tight teeth, use an extra slippery floss.

* To prevent plaque build-up, dentists recommend flossing at least once a day, preferably before retiring.

* It doesn’t matter whether you floss before or after brushing.

* No pain, no gain? Not necessarily, but if your gums are inflamed by tartar--the substance caused when plaque calcifies--there may be discomfort and/or bleeding at first. The good news? Within a few days of correct flossing your gums should heal.

* Tired of sticking hands in your mouth? There’s a new product: FlossPlus, with a battery-operated head that sonically vibrates 20,000 times per minute. It’s $29.95 from NeoSonics Corp., Joliet, Ill. Or you can call that catchy number: (800) 99-FLOSS.

Sources: American Dental Assn.; Los Angeles Dental Society; Johnson & Johnson Consumer Products Inc.; NeoSonics Corp.

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Basic Flossing

1. Break off 18 inchs of floss. Wind one end around one middle finger.

2. Wrap other end around same finger of other hand.

3. Use a gentle sawing motion, curving floss in a C-shape around each tooth until you feel resistance. Repeat.