They say the older you get, the more risks you should take.

Richard Rehak is a Washington dentist. He is very good. He is interested in your teeth, runs expert fingers along your jaw, listens to your bite for signs of stress, does little repairs on the spot for free. Just because he is interested.

But he was not always a dentist. He didn't even start until he was 36. Before that, in a previous lifetime, he tells you casually, he was an orchestra conductor and viola player in his native Czechoslovakia, in Sweden, in Austrailia.

Risks. In 1963 Rebak and his fiancee, Nadezda Slukova, went to London with a Czech folk dance troupe, she as a dancer, he as music arranger. There were 60 people in the group, guarded so closely by plain-clothesmen that they couldn't even go to the bathroom alone.

Slipping out briefly to call a local Czech contact, Rehak got word to Scotland Yard that he wanted asylum. He managed to break away as the Czechs piled out of a tour bus in Kensington. The couple grabbed their bags and sprinted across the street to a waiting car and sped off. Two weeks later they were married.

"We couldn't tell our families about our plans when we left home," he said. "We had to make ordinary goodbyes. That was very hard."

His mother, two sisters and several cousins are still back there. He is still anxious about them and careful what he says. The Communist regime had its eye on him from the beginning. He was too successful.

"When I was 15 I started a color photo processing lab. It was the first one in Czechoslovakia. It was tremendous: I had contact with a big film studio for stills. Within a year, at 16, I was rich. I had 16 employes, worked three days a month. I was still going to school."

There was also the music. At the age of 13 he was playing solo violin in church concerts. Joining the Bratislava Philharmonic as violist, he became part-time conductor, recorded music for the radio, premiered the Shostakovitch 12th and 13th symphonies in Czechoslovakia. He was noticed. Some called him an enemy of the state because he was a capitalist who employed people.

After the escape, the Rehaks moved to Sweden for three years. He played viola and conducted, she was an assistant professor of chemistry at a university. Hoping to reach America, they wound up instead in Sydney, Australia.

They would have to start all over. It was becoming a habit.

"I had no job or contacts, but I saw a woman carrying a viola, so I followed her. She went to a concert hall, and I went in too. The first person I saw was ann old pal from Czechoslovakia who turned out to be the director of the Australia Broadcasting Commission. I auditioned on the spot and found myself a violist with the Melbourne Symphony."

Four years later, his wife was invited to join a chemical firm in Columbus, Ohio, so they packed up once again. Reached Ohio, found no job, decided to come to Washington, which they had visited when the Melbourne Symphony had played at Montreal's Expo '67. Nadezda Rehak went to work as a chemist for NIH. Her husband looked for something in music but discovered he would have to wait six months to join the musicians' union.

"Also, I saw the guy pulling the curtain at the Kennedy Center was making about three times what I would," he smiled. "So I started thinking about denistry. I liked the idea of proving to myself that I could do something entirely new, and excel at it. Everyone told me I was too old. I would have to start at the bottom. I didn't even have math or physics."

Nevertheless, he enrolled at the University of Maryland, supporting himself meanwhile as a department store salesman. His average was 3.96, nearly perfect, and he went into a three-year elite training program with a few other top students, all of whom already had doctorates in their fields. He specialized in periodontistry and oral surgery.

Rehak is 42 now. He has an office on Western Avenue and lives in Bethesda with his wife and son. "I believe in what I'm doing. I like the challenge. I don't think talent means as much as will and a lot of practice." It also helps to have a photographic memory, he added. (He speaks Czech, Slovak, German, Russian, Swedish, English, understands Polish and Serbocroatian, reads Norwegian and Danish.)

But today he no longer practices the viola. He might go back to Europe someday and try music again -- "just to see if I could" -- but at the moment that seems remote.

"You know, this could only happen in America," Rehak said.

Maybe so. On the other hand, maybe just about anything is possible if you're ready to take risks.