In his senior year as a Georgetown University dental student, Alan M. Stark volunteered to teach a group of mentally retarded adults how to brush their teeth.

That experience altered his career -- and it may bring about a change in at least one aspect of dentistry practiced in the Washington area.

When Stark realized the group needed more treatment, he sought help at Georgetown's dental clinic, where "they weren't as well-received as I expected." The staff, he says, had no experience with the hanidcapped. "They were afraid."

He realized then that for the Washington area's estimated 335,000 handicapped "this was a major problem."

Many dentists, he has found both here and in other cities, are reluctant to treat the physically and mentally handicapped.

"It's a shame," says Stark, now on the Georgetown faculty in the Department of Community Dentistry, "that they should suffer from a preventable, correctable disease."

To help alleviate this, Stark, director of dental care for the handicapped, is teaching a new course -- required of second-year dental students for the first time this semester -- aimed at "sensitizing them to the overall needs of the handicapped.

"Nobody taught me about dentistry for the handicapped. I realized this was a deficiency."

In Washington, he says, the handicapped are "classically treated by pedodontists" -- children's dentists. They're the only ones "with any training with patients who are anxious, scared or emotionally upset.

"How do you expect an adult to feel?" he asks, when they must go to an office "where everybody walks around in an apron with a smile painted on it and the chairs are small."

Neglect of teeth is a serious problem among the handicapped, he says. "But how do you teach them home care? It's hard enough to teach normal people to floss and brush."

Only about a dozen of the nation's 60-odd dental schools have recognized courses in dentistry for the handicapped, says Stark. Another problem is that "at least 75 percent" of Washington's dental offices "are inaccessible to the handicapped" in wheelchairs.

With training and "a minimum amount of change in office routine," contends Stark, dentists can include the handicapped in their regular practice, as he does in his two-days-a-week private practice.

He sees it as one more step in "getting the handicapped into the mainstream" of American life.

For a dentist, it's a "matter of understanding their physical and mental limitations" and learning such techniques as how to communicate with the deaf and the blind and how to lift a paralyzed patient from wheelchair to dental chair.

"When you can communicate, you can explain what you're trying to do and allay their fears."

It's also a matter, he says, of getting the dentist "over the emotional stumbling block" he or she might have in dealing with the handicapped. "You don't catch mental illness. Cerebral palsy is not contagious."

For Stark, work with his patients "is like a dance. They lead, I follow.

When they move, I stop."

So that he could make housecalls for the bedridden, Stark, with the help of a dental-equipment manufacturer, devised a portable package with highspeed drill, lights and mouth vacuum.

There is, he says, "a phenomenal need" for home care -- which is why he urges dental students to accompany him. Otherwise, they leave dental school thinking only, "My office is my realm."

Stark, now 29, got his dental degree in 1977, convinced that he wanted to work with the handicapped.

He took his residency training at a large Connecticut facility for the handicapped and the following year was named chief of dental services for the Joseph H. Ladd Center of Exeter, R.I., which housed 755 "severely and profoundly retarded multiple-handicapped people" ranging in age from 2 to 96.

Even there, he found procedures did not always take into account particular problems. One staff guide, for example, outlined 43 steps in teaching patients to brush their teeth.

Stark instituted a "Do-what-I-do" technique, in which patients mimicked his movements while he brushed his teeth a step at a time, "as if they were looking in a mirror."

When a frightened 32-year-old woman, both deaf and blind, showed up with a swollen mouth, he eased her fears first by letting her feel the dental equipment. At the same time, he poured out aromatic oil of cloves to create a pleasant atmosphere in the dental clinic.

Gradually, she relaxed and he was able to pull a bad tooth.

At the Rhode Island center, Stark took a survey of area dentists, asking if they treated the handicapped. One-third said yes. But when he had a dental hygienist phone back saying she had a child with cerebral palsy, "fewer than 3 to 5 percent actually accepted."

Here, he says, "It's the same."

Georgetown invited Stark back, first as a guest lecturer than as a faculty member. With a grant from the Public Welfare Foundation, he developed the curriculum for his course, offered initially as an elective this summer.

Now he is seeking grants to develop a program for dentistry for the elderly and to set up an area in the Georgetown clinic for the handicapped.

Stark says his students also learn how to teach their staff, including receptinists, to be sensitive to problems of the handicapped.

Parents of a handicapped child, he says, often have to put up with long lines and other frustrations when they try to get their child treated.

"All they want," he tells his students, "is for you to treat their child appropriately."