Once out of the elevator, she walked with short, shaky steps down the hallway. Her heart seemed to keep pace with the secretary's typewriter in the first office she passed. The dizziness came in rushes and she was sure she would be sick as soon as she saw the name on the glass door of the next office: Mark A. Wallace, DDS.

Judy Heller had arrived for her dental appointment. Her last visit to a dentist had been five years before.

An estimated 35 million Americans, like Heller, stay away from the dentist until they have a toothache, according to a 1985 National Institutes of Health panel. They avoid the dentist's chair because they are afraid.

People like Heller, a Kensington bookkeeper, are afraid of pain, the noise of the drill, the confinement of the chair, or they simply may fear the unknown. A survey published in the Journal of the American Dental Association in 1983 found that 29 percent of randomly sampled adults in the United States said they were moderately to highly fearful of going to the dentist; 54 percent of them said the fear kept them from seeing a dentist regularly.

The survey was headed by Dr. R.J. Gatchel, a psychologist at the Uniformed Services University of the Health Sciences in Bethesda.

Judy Heller's experience this time was different from past visits to the dentist. Wallace, a cheerful, chatty dentist in Rockville, put her so at ease by carefully explaining every procedure that he could fill cavities without anesthesia.

"This was the only time in my life that I was able to go back to the same dentist twice," Heller said. She now goes to him regularly.

"I've been thrown out of just about every dentist office in Washington," she said. "I really used to get flipped out. I've bitten a few of them really badly. You keep telling them it's hurting and they keep doing it. You have to do something to make them stop."

When she was a child, Heller had some painful experiences in the dentist's chair. And one time she was flying so high on nitrous oxide that she walked into a plate glass window on the way out of the office. "After that I decided to bag the whole thing and wait for dentures," she said. But two years ago, after canceling many appointments, a friend in her office persuaded Heller to see Wallace.

After hesitating at the door, she walked into the bright, carefully decorated waiting area, which could pass for a family room in a modern home in the suburbs. It was furnished with warm yellow and brown easy chairs and couches. Upbeat light rock stirred the air in the room. And a long table was neatly lined with enough different kinds of magazines to satisfy the tastes of 25 patients. "What we did with Judy was to get her to relax," Wallace said. "If you're straightforward with them, you can do anything. Get them at ease. Let them know what's coming. I've had a lot of fun getting people to trust me enough not to need Novocain. It's all in the talking. Let them know you care about them."

With some anxious patients he spends 50 minutes of an hour talking and a few minutes working. When it's over he gives the fearful patient a yellow "Bravery in the Dentist's Office" button.

But before a dentist can begin to ease a patient's fears, the patient must show up at the office. One of Wallace's patients used to call him from the shopping center across the street when she was brave enough. "I'm this close -- can you fit me in?" she would plead. Now she is able to make appointments further in advance.

Many people, like Aspen Hill medical artist Alfred Laoang, trace their fears to unpleasant childhood experiences.

He recalls a day at the dentist nearly 40 years ago, when he was 7: "The Novocain didn't take, but I was afraid to tell the dentist. So I let him pull my tooth. My mother said she saw one tear roll down my cheek. I didn't let out a yelp. She said I was holding on to the chair so tightly that my fingers turned white. It took two years to get my toes uncurled."

As soon as he was in college, Laoang stopped going to the dentist until he lost a filling. It had been eight years between appointments. He has since found another dentist. Most fears about facing pain in the dentist's chair, though, are unwarranted in light of improvements in preventive measures, techniques, anesthetics and tools, said Dr. Raymond A. Dionne, a staff member of the pain clinic of the National Institute of Dental Research. "People come in today in their late teens to have wisdom teeth out," he said. "They don't have any fillings. Due to dental sealants and fluorides, they just don't need the restorative work they did 10 years ago. Now you expect not to find something when you see them for a cleaning."

And on those rare occasions when work is needed, Dionne said, the effective use of a topical anesthetic to numb the gum and a shot of Novocain to numb the tooth, filling teeth has become "virtually painless." Improved drugs given after difficult procedures also alleviate pain.

"The problem with some of these patients," Dionne said, "is that the only time some of them end up in the dental chair is in acute pain with a bad infection. Local anesthetics don't work as well then."

Another NIDR researcher, Dr. James Lipton, has found that some patients avoid treatment because they are afraid to admit their fear of the dentist. "They don't want others to see they are afraid, they don't want to complain about pain," he said.

Lipton, who is involved with several NIDR-funded research projects dealing with dental pain and its control, has seen patients with very specific dental fears. "Some are afraid that if the dentist works on their upper teeth, the drill might slip and go into their cheek, their eye or even their brain."

Watching closely for signs of pain or uneasiness are important to Dr. Kay D. Klass, a Northwest dentist known for her sensitivity to patients. "I hear about dentists who will be talking about a baseball game with an assistant, ignoring the patient in the chair. You need peripheral vision. I focus on the tooth, but out of the corner of my eye, I try to watch for that raised eyebrow. I ask them if the procedure bothers them. I am careful not to use the word 'pain.' I tell them it is okay to be scared. All of this shows them I care."

In addition, she asks anxious patients to do breathing exercises to keep their minds off the procedure and allows others to use their own headphones to listen to music while in the chair.

Klass, who has been in practice only a few years, uses a technique practiced by old hands such as Dr. Francis J. Samaha, a McLean dentist who has been seeing patients for more than three decades: Both spend up to two hours on a first appointment talking to anxious patients.

Samaha, former president of the Northern Virginia Dental Society, says "you must take the time to communicate with them. Don't work too fast. You have to have the patience to treat patients like important human beings. Be very honest and don't promise what you can't deliver."

To Dr. Edwin J. Zimmet, another Washington dentist, going slowly also is critical. "I charge patients by the time I spend," he said. "I use an hourly rate so the patient understands you won't be impatient with them. I tell the anxious patient I can put up with anything. A lot of them feel guilty about taking a lot of time. I tell them it's paying my bills."

While there are dentists in the area like Zimmet, who try to relax fearful patients, others rely on gas. One Northern Virginia dentist has a hospital anesthesiologist on his staff to put anxious patients to sleep.

According to NIDR's Dionne, however, "we have found that in the long run, anxiety can be handled better by using behavioral techniques rather than with general anesthesia."

Some fearful patients have developed a phobia -- an irrational fear of the dentist's office -- and they need a bit more than careful attention, according to Jerilyn Ross, associate director of the Roundhouse Square Phobia Treatment Center in Alexandria. These phobics, she says, are afraid of sitting in the chair and being trapped, or losing control and screaming: "Let me out of here!" It is a fear of their own panic.

Ross tells these patients they should not try to block out the fearful feelings but, rather, try to focus on something else. Then the panic will pass quickly. She says that she gives phobics rubber bands to snap and suggests that they put cologne on their arms and smell it when panic begins to rise, or she asks them to count backwards from 100 by threes.

As part of the treatment, center staff and former phobics go to appointments with the patients and work with the dentist to make the experience less threatening. The main thing, according to Ross, is that "they need an out -- no matter how wild -- like having the dentist stop." Sometimes, she adds, the patient needs to be able to walk around or leave the office for a while.

This approach has helped Merle Baboyan, who has a fear of going through an anxiety attack in the dentist's office, among other places. Baboyan, who runs Dental Power International, a Washington area firm that provides staffing and consulting services to dentists, says "being in the dentist's chair isn't the ultimate trap -- but it's high on the list."

Through the phobia program she says she has learned that she can have an anxiety attack anywhere, so there is no point in running away. Now she just tolerates the panicky feelings, focuses on something else, and in a short while she feels fine.

Phobics and others fearful of the dentist often have problems because they stay away from the chair for so long that any past bad experiences are magnified. A trip to the dentist becomes an hour on the rack, a very slow walk over very hot coals.

And there are some mental health and dental researchers who believe that today's greatly improved dental care in this country actually may be increasing the number of frightened patients. The theory is that children so rarely have cavities -- with fluorides and dental sealants in use -- that they forget how little discomfort they felt the last time they had a filling, and their imaginations take over.

Clearly, competition in dentistry has increased in recent years. The American Dental Association reports that there were some 111,000 dentists in the United States in 1976 compared with an estimated 136,000 this year. And while there is no hard data on how many dentists have focused on fearful patients to grab more business, ads saying "We Cater to Cowards" have begun to appear in recent years.

Another indication that dentists are becoming more interested in treating anxious patients is the emergence of fear clinics at a few hospitals and dental schools. There, dental phobics see the fear clinic staff before going to the dental clinic.

Dionne urges that dentists take advantage of what has been learned about dealing with the fearful patient. He says that in the days when there were so many more patients than dentists, the dentists could take their pick.

With many more dentists practicing today, though, competition is much more fierce and, he warns, "a stale joke, a slap on the back and a return to 'hold still!' just won't work anymore."