When Judy Laniak learned last year that her daughter, Leia, needed more than $4,000 worth of braces for her teeth, she worried about the cost, but she didn't hesitate to start treatment.

"You just have to close your eyes and do what you can do," said Laniak, of Alexandria. Leia, 11, had a slight lisp from a gap in her teeth and received a full set of braces in July and is doing well. "It has to be done. I want her to go through life with a nice straight smile, rather than grow up and say, You never did this for me.' "

It's a feeling that many parents share. They want to provide the best for their children, and a nice, beautiful smile offers certain social advantages not limited to television anchors.

As a result, braces have become almost a rite of passage in the United States. The number of youngsters receiving them has quadrupled since the 1960s. An estimated 4.5 million Americans -- most of them children and teenagers -- wear braces on their teeth, according to the American Association of Orthodontics. About 80 percent of those undergoing orthodontic treatment range in age from 6 to 18 years old.

The investment in time -- and money -- can be steep. "A lot of parents don't anticipate what an intrusion this is going to be for two to three years," said Camilla Tulloch, associate professor of orthodontics at the University of North Carolina School of Dentistry in Chapel Hill. "For early treatment, you see the orthodontist every six to eight weeks, but once you're in full braces, you are seeing the orthodontist every month, and sometimes more often when things break."

Orthodontics treatment runs as much as $6 billion annually -- on average about $4,000 per patient -- and it is not covered by most dental plans. That makes braces "one of the . . . major out-of-pocket expenses that families face," said Lysle E. Johnston Jr., head of the orthodontics and pediatric dentistry department at the University of Michigan in Ann Arbor.

Yet there are few scientific studies that have tested the use of braces and their long-term efficacy. "After all, this is not cancer, AIDS or heart disease," Johnston said. "It's an elective procedure."

No one knows which treatment lasts the longest. No one knows whether the sleek new braces made out of materials such as nickle-titanium alloys are really superior to the clunky, old stainless steel. No one can point and say this child's teeth will stay straight until old age if you pull some of her teeth now before putting on braces while another child's teeth won't.

Only in the past few years have researchers begun to examine which treatment is best for which patient and to ask when using braces is most appropriate. Should braces be put on early when baby teeth are still present and jaws more malleable? Or is it better to wait until all the adult teeth have come in and the jaws are more mature?

"We definitely need long-term studies, but this is like all of medicine," Tulloch said. "Techniques are changing, and we are doing treatments today that are unlike those that 40-year-olds had when they were children. It's a difficult path, and we can't answer all the questions."

But braces are now such an accepted part of childhood that the very parents who would normally grill health professionals before allowing their children to undergo another medical procedure rarely stop to ask about the medical necessity of braces. They generally don't seek second opinions or examine the credentials of those who provide orthodontic treatment.

Most, like Lydia Bonner of Potomac, simply rely on their dentist's referral to an orthodontist. "My dentist asked me if I wanted the best orthodontist or a good orthodontist," she said. "I told him I wanted the best."

Normally, Bonner said, she seeks second opinions for medical procedures. "But when I knew I had the best," she said, "I didn't even get a second opinion."

In Bonner's case, it turned out well: She is pleased with the treatment. Her orthodontist graduated from an orthodontics program after finishing dental school and is board-certified. But many other dentists are not, according to the American Board of Orthodontics. Only about 25 percent of practicing orthodontists have passed certification exams and the majority of patients are treated by general dentists who don't hold board certification in orthodontics and have little, if any, formal training in the specialty. Why Braces?

Had orthodontists existed in prehistoric times, primitive humans probably wouldn't have needed their services: The dental problems that plague 20th-century humans are a relatively recent development.

Fossil records show a steady decline in jaw size during the past 1,000 years. At the same time, the number and size of teeth have also diminished but not as fast as jaw size. Experts say it is that combination that has led to the orthodontics problems that are so common today. The latest estimates suggest that more than half of children in the United States have some need for orthodontic treatment, according to the results from a government health survey.

For years, orthodontists have identified three major types of dental problems that require braces. Collectively, they are called malocclusions, from the Latin for "bad opening." In a class I malocclusion, the jaws and molars are properly aligned but the teeth are crooked and crowded. In class II, the molars are misaligned and the upper jaw protrudes too far forward, the condition commonly known as "buck teeth." In class III, the molars are the most misaligned and the lower jaw juts in front of the upper jaw.

The goal of orthodontics is to treat these problems in the hopes of preventing others, including gum disease, temporomandibular joint pain, trauma, tooth decay and speech disorders by redirecting growth of jaws, stretching ligaments and improving spacing between teeth.

Braces also nearly always improve appearance. "If you are socially embarrassed by how your teeth look, it can have a profound effect," Tulloch said. "It is wrong to dismiss {the effects on} appearance too lightly."

But for many the treatment is far more than just cosmetic. A 1974 National Academy of Science report found that up to 14 percent of youngsters have dental problems so sever that they are considered handicapping because they affect breathing, speech, eating or appearance. Range of Treatments

Since most people have a combination of problems, however, there is great debate about the best way to correct tooth irregularities and wide regional variation in how it's done and even in the materials that are used. Some orthodontists want to treat children very early, while others advocate waiting until they are near their teenage years. Some believe that removing teeth is necessary, and others will go to extremes to keep from doing that. Some use headgear for the children and others don't. And there are a variety of theories about how long retainers should be worn to keep teeth straight after braces are removed.

"Each school of orthodontics tends to have a slightly different philosophy," said the University of Michigan's Johnston. "We're talking about subtle differences . . . but the problem is that in 1998 there are pressures from the public and from within dentistry to treat in methods that may not be effective."

Among the problems, he said, is a reluctance among orthodontists to alter their treatments based on the patient's individual needs. For example, he said, an orthodontist may have learned that a class II malocclusion is best treated first with a retainer, then a device that will spread the palate followed by braces. But, he said, for some of these patients that approach may not be the best and the child could do better having teeth extracted and going directly to braces.

Orthodontists need to be willing to vary from the rigid treatment plans that they learned during their training, he suggested. "Certainly they simplify decision-making (as would a coin toss or a turn at the Ouija board), but do they make sense?" Johnston noted in the Australian Orthodontic Journal. He added that orthodontists have become so averse to skepticism about their treatments that "any doubt, any equivocation, any hesitation is seen as an impolite, anti-social and unmutual' threat to the public health."

Another difficulty in assessing treatment is a tendency for orthodontists and dentists to jump on the latest treatment fad -- one reason that tooth extraction has cycled in and out of favor over the years. "All the big, big arguments {in orthodontics} are by and large being conducted without much evidence," Johnston said.

As he noted in a 1998 guest editorial in the journal Angle Orthodontist, "Given the disparate nature of contemporary treatment strategies, it would be remarkable if all were equally effective. It would be even more remarkable if any single treatment . . . could achieve optimal results on . . . all patients . . ." Early Versus Late Treatment

Among the latest trends is an effort by some orthodontists to identify children who will have crowding problems early and to treat them as young as possible and to avoid extraction of teeth at all costs. In place of pulling teeth, orthodontists use headgear that is worn at night to help expand the upper jaws and move the teeth into correct position.

Proponents of this approach argue that by putting braces on children as young as 6, they can do what nature may not: re-mold jaws and coax teeth to go straight. "There are newer devices that allow us to harness growth to our advantage," said Jeremy Orchin, a Washington orthodontist who uses early treatment in his practice. "A lot of children can benefit from early treatment."

But others are not convinced. "It's a very tempting idea to think that you can be in there {in the mouth} and diddling around and reorganizing nature so that everything will be perfect by age 12," said the University of North Carolina's Tulloch. But she cautioned that such efforts may be premature.

"Young children . . . grow their permanent teeth when they're about 6 years old," Tulloch said. "At that stage they have kind of childish-looking faces and childish-looking jaws and everything looks like a mess. It's quite hard to predict which children will have sufficient space and which will not."

Advocates of the early treatment say that young bones are more pliable and young children are easier to handle and more cooperative than moody teenagers, making a better experience for all involved. "Kids are highly motivated at that younger age," said Orchin. "The tissues respond favorably, and the kids are excited about having braces."

Christy Walker was just 7, with a snaggletoothed smile, a classic overbite and many of her baby teeth still intact, when she began treatment 10 years ago. Christy's mother, Deborah Nowlan of Bethesda, said that she "worried that a 7- or 8-year-old would be traumatized by it. The big surprise to me is how easily the kids adapt to braces when they are young. . . . I remember having braces {as a child} and just hating it."

The other big benefit of early treatment for Christy was that by the time she celebrated her 14th birthday, her braces were off and her teeth were straight.

But a recent study, funded by the National Institute of Dental Research, suggests that early treatment does not necessarily shorten treatment for most children with classic overbites and may, in fact, prolong treatment for some.

The 10-year study of 175 youngsters was conducted by William Proffit, chairman of orthodontics at the University of North Carolina, Tulloch and their colleagues at Chapel Hill and published earlier this year in the American Journal of Orthodontics and Dentofacial Orthopedics. They randomly assigned participants to be observed only, to receive headgear or to get a retainer, a functional appliance that can be removed, but looks a bit like "mini" braces. During this first phase of the study, children were monitored for 15 months.

As a group, the observation-only participants showed no average change, although there were individual variations. For example, 5 percent of youngsters in this group improved on their own, while 15 percent of children worsened during phase I of the study.

Children in both treatment groups improved significantly, but "by no means did all patients respond as one might have expected from the pattern of average changes," the team of researchers reported, noting that up to 25 percent of children showed no response at all.

Youngsters who wore headgear and those who received retainers showed the most improvement in the upper jaw, the maxilla. Seventy-six percent of those with headgear improved, as did 83 percent of those with retainers. Thirty-one percent of the children who did not receive treatment also improved.

During the second phase of the study, children who still needed orthodontic treatment were given braces. Preliminary findings from this phase showed that early treatment did not shorten the length of time that children spent in orthodontics treatment and in fact "the total time in treatment was considerably longer" than the average for children who gets braces at an older age.

The team concluded that "there is little to be gained from precisely timing early treatment to specific age/maturity markers." To Pull or Not to Pull

Tooth extraction is another controversial issue facing orthodontists, who have debated its merits and problems for decades. Normally, extraction means pulling two to four teeth to provide space on both sides of the face as well as the upper and lower jaws.

The University of North Carolina team found that the need for extraction was less in those children who wore headgear versus retainers prior to getting braces. But what no one knows is how long this kind of treatment without extraction will last.

"As we get older, three things happen: gray hair, wrinkles and teeth shift," Orchin said. "So the most difficult problem for orthodontists is retaining the result that has been achieved."

Many orthodontists believe that a select group of children, especially those with a class II overbite, can benefit enormously from extraction and that without it, their teeth are doomed to go back to their old jumble.

"There are pressures to treat without extraction," said the University of Michigan's Johnston. "Parents have been told that extraction is tantamount to mutilation. They say We want macrobiotic, holistic dentistry,' and that's total nonsense. . . . There is a class of patients that can be uniquely helped by extraction." Who Really Needs Braces?

The 1974 National Academy of Science report found that the index used to judge "normal" jaw alignment and tooth placement was restricted to a "highly arbitrary standard" seldom seen in the general population. "Until an acceptable definition of normal' occlusion is developed," the report noted, "malocclusion will remain ill-defined."

Since then, a team of orthodontics experts has developed an index that grades the severity of the dental problem on a scale of "no treatment necessary" to "definite need." Based on this index, more than half of all children in the United States need "at least some degree of orthodontic treatment," according to a new study by Proffit and his colleagues at the University of North Carolina.

About 40 percent of youngsters have mild to moderate crowding of teeth in both jaws and problems with misalignment, the study found. Nine percent of children surveyed had severe crowding and misalignment and about 3 percent of the population had extreme dental problems. The researchers also found a "moderate" or "definite" need for braces by ages 8 to 11 in 52 percent of white youngsters, 53 percent of black children and 27 percent of Mexican American youngsters.

The team's conclusions are drawn from data collected in the third National Health and Nutrition Examination Survey conducted from 1989 to 1991 by the federal Centers for Disease Control and Prevention.

How many youngsters actually receive treatment is often dictated by their family's financial status. Children in families with incomes of $50,000 and higher are twice as likely to wear braces as those from lower income groups. But the treatment gap is narrowing slightly, since all states now offer some orthodontic care to Medicaid recipients. Five percent of the lowest income groups and 10 to 15 percent of children from families with intermediate incomes now also receive orthodontic treatment, according to the study -- one measure of how highly valued this treatment is.

Flexible payment plans have eased the financial burden by allowing parents to pay for treatment as their child receives it. Several new companies also offer low-interest loans, with payments spread out over three to five years. Health care spending accounts can ease payments more by providing pre-tax dollars for orthodontic care.

As a result, more than 30 percent of white youths, 11 percent of Mexican American youngsters and 8 percent of black children received braces, according to the latest figures.

Despite the hassles, the time spent in treatment and the money involved, the results can be very gratifying -- even for the youngsters.

Ryan Poole, 14, of Mitchellville, got his braces when he was 12. "At first when I wore them, I didn't like them that much," said Ryan, who described his teeth as feeling like they were caught in a vise.

"They seemed a little annoying in the beginning," he said. "But later on I got used to them and they felt regular."

The hard part about wearing braces was the treats that Ryan had to give up. "I didn't like that about them," he said. "I gave up taffy and Skittles and some of my favorite candies and bubble gum."

Since the braces came off in July, Ryan knows what a big difference the last two years of orthodontic treatment have meant to his teeth, which he says were very crooked. "I saw a sculpture of what my teeth looked like two years ago and what they look like now," he said, "and it's a really big improvement." PERCENT OF U.S. CHILDREN NEEDING BRACES

White Black Mexican-American NO NEED

57

47

48 MODERATE

29

31

40 DEFINITE

14

22

12 Already had treatment

27

6

12 SOURCES: National Nutrition and Health Examination Survey III, 1989-91; International Journal of Adult Orthodontics and Orthonagthic Surgery, 1998; William R. Profit, DDS, University of North Carolina, Chapel Hill. CAPTION: JULIE POCKROS, 7, ADJUSTS HER HEADGEAR. ec CAPTION: Ilana Sushner, 13, above, chose multi-colored bands, one of many new options to make braces more appealing to kids. Below, headgear adorns Julie Pockros's doll and her brother's stuffed bear. ec CAPTION: Brian Bullock, left, and his sister Alison find that their braces don't keep them from any of their athletic activities, including baseball, soccer and bowling. ec CAPTION: Young children, such as Julie Pockros, are now routinely getting orthodontics treatment. ec