Now come the dentists to tell us that milk is dangerous for our babies' teeth.

Milk? With all that calcium and vitamin D and all those other good things? Milk?

Sweet juices, too, the dentists persist.

Not so much the milk itself, says pediatric dentist Sylvan S. Mintz, but a combination of whole milk, which has lots of sugar in it, and the oh-so-popular practice of putting the baby to bed with the bottle, and letting the bottle feeding go on past a year, sometimes even up to and beyond two years.

What happens, says Dr. Mintz, taking time out from his Southern Maryland practice to do his bit for National Dental Health Week (beginning Feb. 4), is this: "The milk or the fruit juice pools around the teeth -- they're not really drinking it -- and they fall asleep. It sits there and ferments and does the same thing to the teeth as a cola drink or a chocolate bar."

Because the primary (the dentists don't like to call them baby) teeth have only about one-eighth the enamel of permanent teeth, "the decay process is very quick."

Often, while it is happening, the parent won't notice until the cavities become obvious, or the child starts to complain that cold milk, for example, hurts his or her front teeth.

"It's such a simple thing to prevent," he sighs. "And when parents come in wondering 'What's wrong with my child's teeth?' and they find out . . . they just cry."

And, of course, treating the teeth of a young child is complicated and expensive. It often requires hospitalization and a general anesthetic. Dr. Mintz recalls a 3-year-old where "out of 20 teeth in the child's mouth we did 19 crowns and one extraction."

He estimates that in the Washington metropolitan area, 6 to 12 children under 3 are admitted to hospitals each week for this kind of dental work. It can mean a couple of nights and $600 or $700 in hospital fees, plus dentist fees (mostly not covered by health insurance), says Dr. Mintz. Children's, Holy Cross and Prince George's General are especially well-equipped, he says, but even so, it doesn't have to happen at all.

"Sometimes nothing is done," says Dr. Mintz, "and the teeth are left to just rot to the gum. With kids 3 and 4 years old there's nothing left of the teeth and nothing for the dentist to do but take out the little root tips.

"It's a big problem, and it knows no socio-economic class. I have nurses' children and physicians' children . . ."

It does not, of course, happen to every baby who's put down with a bottle of milk or juice. "It's host related -- if you're susceptible, you'll get it and the next person won't. I have grandmothers who'll say, 'Well, I always put Mary to bed with her bottle and nothing happened to Mary, so why do we have this problem with Mary's child?'"

Another problem, Dr. Mintz says, is the widespread attitude that asks, "Why do we have to care about baby teeth, anyway?"

Don't forget, he says, it isn't until a child is about 6 that he gets his first front tooth, and the last "baby" tooth doesn't come out until about age 13. In addition to looking different from the kids in the nursery school, a baby without front teeth is more likely to have speech problems and an eventual need for expensive orthodontia.

Pediatric dentistry is a relatively new field, and that may be why the "babytooth problem seems like something new. Dr. Mintz believes that it hasn't worsened over the years, "but it hasn't gotten better."

And diet -- meaning too much sugar -- is the big culprit.

Dentists are now telling new parents to bring in youngsters at the first sign of the first tooth. "Not so much to look into the child's mouth," says Dr. Mintz, "but to talk to the parents about what they can do to protect it."

He suggests first, of course, not letting the baby sleep with a bottle of milk or juice, switching the baby to lower-fat milks (with the pediatrician's approval, of course) at about 6 months and weaning the child from the bottle altogether by a year.

In addition, it is a good idea to gently wash the baby's teeth and gums with a clean washcloth after the bottle or after nursing. Yes, Dr. Mintz says, almost apologetically and a little uneasily, mother's milk too, has been targeted in recent studies as a cavity-producer, again, usually when the infant is brought into the mother's bed at night and falls asleep nursing.

As the child grows, so do the problems. Fluoride help significantly in areas where it has been added to the water supply. And good brushing habits also are important.

But it all comes back to diet. And again, milk is one of the major culprits.

"We find some of our biggest cavity producers are the big milk drinkers," Dr. Mintz says. "Some of these kids are going through a quart of milk a day, and big milk drinkers tend to be big cookie eaters, big donut eaters, which also adds to the problem."

People, he says, are so brainwashed about the importance of milk that they are inclined to do almost anything to encourage milk drinking. As in adding chocolate.

Of course it is the sugars in milk and chocolate and almost everything else we give our kids these days that produce the acid-making bacteria that eat away the teeth.

In a booklet he hands out to patients, Dr. Mintz notes that "one teaspoon of sugar enables the bacteria on the teeth to produce 20 minutes of acid immediately."

And "the frequency of sugar intake is more important than amount. Between-meal sweet snacks are more harmful than when eaten with a meal."

He suggests popcorn, pretzels, nuts and fresh fruit as better snacks. Even potato chips are better for the teeth than sweets.

And finally he warns new parents of the dangers of hidden sugar: That tried-and-true luncheon sandwich, peanut butter and jelly, has the equivalent, he says, of 15 teaspoons of sugar.

In effect, the dentists' message is this: If your child has a sweet tooth, he likely won't have it long.