In 1970, the dean of Harvard's School of Dental Medicine attended the traditional Commencement Week alumni outing, expecting to perform his usual ceremonial duties: to greet the 25-year and 50-year reunion classes.

But that year there were no nostalgic dentists for Dean Paul Goldhaber to greet. In both 1920 and 1945. Harvard's dental school hadn't had a graduating class, because of changes in the length of the school's program.

At Commencement gatherings in 2008 and 2033, another dean will find himself in a similar plight. Because of a 1979 curriculum overhaul that made Harvard's the only five-year dental program in the country, no one will graduate from the University's dental school this June.

Change comes quietly to the School of Dental Medicine, the smallest of Harvard's 10 graduate schools, and indeed the smallest of the nation's 60 dental schools (current enrollment is 80). But behind the phenomenon of this year's missing class is an innovative shift in thinking about the role dentists should play in society.

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In its present incarnation, the school's curriculum includes the currently standard two years each of science and clinical dentistry--the first two taught at the Medical School and the last two at the dental school (by a separate division of the Medical School's faculty).

The new fifth year is devoted either to biomedical research towards a three-or four-year postdoctoral program, or to study at another graduate school such as the School of Public Health or the Kennedy School of Government.

Aside from a couple of dull reunions in the 21st century, the main result of the revised program, says Goldhaber, will be dentists who can "interact on a level that straight dental technology does not provide." As Goldhaber sees it, dental medicine should eventually become "a hybrid--combining the art and science of dentistry with biomedical research or with knowledge of health-care delivery systems." In short, the school now seeks to train practitioners whose skills encompass not only dentistry but also the broader field of social medicine.

This fall, Goldhaber will keep an especially close watch on the first group of dental students to enter their fifth year. Nine or ten--about half the class--will study at other schools, while the remainder pursue further medical research.

For their part, the students express reservations about the five-year program, but most look back on their decision to enroll at Harvard with contentment. The extra training, many say, outweighs the cost incurred by an additional year of tuition and foregone earnings.

"To be quite frank with you," says Robert A. Barnett, who is on leave doing research after his second year. "I didn't see the extra year as an advantage when I was choosing schools." But he adds, "I have a strong interest in research, and the strength of the Harvard program is that you get the strong medical background--I didn't want to be a general dentist."

Rosemary D. Bria, also on leave after her second year, says that she chose to attend Harvard because she "wanted simply what the program as a whole could offer me." She says that if Harvard had not accepted her, she would have chosen to attend medical school, explaining. "I did not simply want to be a clinical dentist."

And fourth-year student Gary R. Login, anticipating a fifth year of research "really developing a multi-discipline career," says. "I thought I was getting a much better deal in five years than I would in four--I wasn't looking to get out fast."

Richard F. Black '77, another fourth-year student, had a harder time deciding to come to Harvard. He cites financial disadvantages such as increased tuition and decreased productivity, but concludes. "I decided, as did my classmates, that the benefits would probably outweigh the cost."

Even with the extra year, tuition and fees for the School of Dental Medicine are only the twelfth most expensive in the country at $50.286. The national average is $29.453, but most dental schools offer three-or four-year curricula.

In part, the new five-year program was designed to overcome objections about the school's small size. Goldhaber says. Unless the graduates went on to achieve extraordinary success and had "some sort of ripple effect," says the dean, "one could question whether with that small enrollment it was worth having a dental school."

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But the absence of a graduating class this year doesn't faze the school's administrators--it's happened before. In 1917, for instance, the school went from a three- to a four-year program, wiping out its potential 1920 Commencement line-up.

Then in 1941 came a change in name, from the Dental School to the School of Dental Medicine, and along with it, a new five-year curriculum towards both the M.D. and dentistry degrees. But as Goldhaber explains it, the armed forces disapproved of the time-consuming double degree and, with a military fervor sweeping the country, the school decided to change its program once again.

This time, the school tried a six-year curriculum involving two years of basic science at the Medical School, two years of training in clinical dentistry, and the option to return to a Harvard-affiliated hospital for two years of clinical medical training and a medical degree.

In 1954, however, this option was removed from the curriculum. "Too many students ended up M.D.'s rather than in dentistry," Goldhaber says. Today, dental students do have the option of completing the first two years of the program and then transferring to a medical program, although the medical school cannot be Harvard's.