Dr. Daniel Bernstein, early backer of fluoridation, activist

Voice faint from cancer treatment, Dr. Daniel S. Bernstein lay in a bed in Brigham and Women's Hospital, where he had treated the ailing and the infirm for so many decades. He had wanted to practice medicine his whole life, and with his hours of consciousness waning a final task remained, so he dictated one last letter to his patients.

"He told me the day his memory became less sharp would be the day he stopped practicing, but he never got to that point," said his daughter, Carolyn, of Newton. "He remembered everything."

A researcher turned academic, he always kept a clinical practice going and during the past 51 years developed the kind of wide-ranging diagnostic skills that are as rare today as a doctor who makes house calls. Dr. Bernstein died Wednesday, two days after bidding farewell to his patients in that letter. He was 80 and had lived in Cambridge and in Chilmark on Martha's Vineyard.

"He had this incredible ethic," said his son Jeffrey of Newton. "Even while he was at the Dana Farber getting his own treatment, he'd be checking his voice mail and pager and checking in with his own patients."

"My father always said, 'If I want to spend 45 minutes with a patient, I don't care what any health plan says, I'm not going to spend only 15 minutes,' " said his other son, Andrew of Brookline.

An early proponent of fluoridation, Dr. Bernstein's research helped establish its advantages, and he told the Globe in 1983: "There is one basic, irrefutable fact, and that is all water, everywhere, contains fluoride. It is not an additive. Fluoridation is an adjustment of that level, and at one part per million, its dental health benefits are great and it is nontoxic."

He was just as outspoken about the Vietnam War and nuclear proliferation -- he opposed both -- and how the state should go about burying low-level nuclear waste. In 1986, he testified before a legislative committee considering options that ultimately were beholden to the will of the voters.

"It's a very complex issue and should not be subjected to a referendum vote," he told the panel. "I'm a physician and am certainly not in favor of referendum votes that decide something as complex as radioactive waste disposal."

Born in Baltimore, he was the son of a traveling salesman who sold pants. His father was as devoted to his children as Dr. Bernstein would be to his. Graduating from high school at 16, Dr. Bernstein enlisted in the Navy near the end of World War II, and his father once traveled 17 hours by train to visit him while he was stationed in Mississippi.

Dr. Bernstein majored in English at Haverford College in Pennsylvania and put himself through the Johns Hopkins School of Medicine in Baltimore by doing odd jobs. He married Marjorie Hiatt of Worcester and they celebrated 53 of marriage a few weeks before he died.

"My parents met on a blind date through a family connection and fell in love right away and actually got engaged after three weeks," their daughter said. "They had the most romantic relationship. They really understood each other so well."

The couple moved to London when he received a fellowship in endocrinology, then lived in Durham, N.C., before returning to Boston, where Dr. Bernstein had served his residencies. His early career was spent researching areas such as bone metabolism and the parathyroid hormone.

"He loved the pituitary gland," his daughter said. "He would tell me it was the master gland and ran everything."

A vocal critic of the Nixon administration during the Vietnam era, Dr. Bernstein found that his research funding began drying up and suspected the reason was political, rather than scientific. Offered a position at the Boston University School of Medicine, he became an associate dean and professor, a post held nearly 20 years beginning in the mid-1970s.

"My father, as a physician, had a sense of peace and justice in the world," Jeffrey said. "Even up to last week he was reading the columnists he liked and railing about the Bush administration."

Throughout his years in research and academia, Dr. Bernstein kept a clinical practice and saw patients -- including those too poor to seek treatment elsewhere.

"If people came in and they couldn't pay, he wouldn't charge them," Andrew said. "And he always dictated his notes in front of his patients so they knew what was going on."

For years he volunteered in Cambridgeport, helping patients outside the sphere of conventional healthcare.

"It was a free clinic, it was street people, mostly drug users," Jeffrey said. "He worked long hours, but he went over there. He felt it was his obligation. He would tell us stories -- he was seeing a lot of junkies and people who were in really tough shape. He was a Jimmy Stewart, 'It's a Wonderful Life" kind of guy. If he could put people on a path and redirect a life, he would."

Habitually upbeat, Dr. Bernstein kept a ready store of aphorisms that he dispensed along with his medical advice. And he had "a series of expressions for something that didn't make the grade," Jeffrey said. "A lousy pitcher or a lousy restaurant was 'El Junko.' The food out on Yawkey Way -- that was all El Junko."

An avid tennis player and music lover, Dr. Bernstein also had a passion for reading, devouring everything from John McPhee's nonfiction and Ken Follett's thrillers to novels and historical tomes. And, not surprisingly, he kept current on medical literature.

"I'm a neurologist, and whenever I had a primary care question, I called him and he always knew the answer," his daughter said.

After retiring from Boston University, Dr. Bernstein continued his practice through an outpatient group at Brigham and Women's.

"He had one patient he referred to me, and she said, 'I've known your father longer than you have,' " his daughter said. "He had treated her for 50 years."

Dr. Bernstein had hoped to return to his practice in September, and many of his patients would not change doctors on the chance that he would.

Last Monday, Andrew played for his father a recording of Franz Schubert's "Trout Quintet," Dr. Bernstein's favorite piece of music, and his brother kept a bedside vigil.

"I didn't sleep that night for obvious reasons," Jeffrey said. "He told me to turn the light on so he could look at me. It was maybe one of the last things he said; he lost his language early Tuesday morning. He just whispered that. That was my father."

In addition to his wife and three children, Dr. Bernstein leaves his sister, Betty Taymor of Cambridge; two grandsons; and three granddaughters.

A celebration of his life will be held at 4 p.m. on Sept. 16. The location will announced. E-mail jbernstein@hurricanelodge.com for details.