Twice a week, Mark Swerdloff sells tickets at the local multiplex movie theater.

It’s a nice job for a retiree, Swerdloff says, except that he’s not exactly retired.

Swerdloff, an oral surgeon and professor emeritus at Stony Brook University’s dental school, continues a 40-year consulting stint at Northport Veterans Affairs Medical Center, serves on the board of a liability insurance company, conducts peer reviews for insurance claims, acts as an expert witness in malpractice cases, works as a polling place inspector on election days and recently was facilitator at a professional association round-table discussion in Washington, D.C. He is married and has two grandchildren.

For him, spare time is like a tooth cavity. It needs to be filled.

Selling movie tickets for $10.10 an hour? Why not?

“You can’t just sit around,” says Swerdloff, 71, who lives in Stony Brook.

Making the most of life is Swerdloff’s grand scheme. He almost didn’t have the chance.

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On Nov. 30, 1968, three weeks before their wedding day, Mark Swerdloff, 23, of Coney Island, and Carol Roth, 22, of Sheepshead Bay, were driving through Brooklyn in a Ford Country Squire station wagon owned by Swerdloff’s family.

Somewhere — he no longer is sure of the location — the car stalled. Swerdloff, a second-year dental student at Columbia University, got out to push the Ford clear of traffic. Another motorist stopped to help. Both shoved from the rear. Swerdloff faced front. The second man put his back against the wagon and could see down the street.

As the two got the car rolling, the stranger called out, “We’re going to be hit!”

Swerdloff didn’t have a chance.

An oncoming car sheared off one his legs and damaged the second so badly it had to be amputated at Coney Island Hospital, where Swerdloff was taken by ambulance.

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No one else was hurt. Swerdloff barely survived. “I shouldn’t be here,” he says.

What became of the other driver, Swerdloff doesn’t know. He shrugs. Nothing can change what happened that day.

It’s what happened next that counts, Swerdloff says.

At first, he could only cry. The amputation was severe. Swerdloff was left with two stumps ending a few inches below the groin.

“It was painful to watch him struggle, knowing what his dreams and hopes were and just praying that he’d be happy and have a fulfilling life,” says Swerdloff’s sister, Robin Young, an intermediate-school principal in upstate Brewster.

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For Swerdloff, dreams trumped despair. “After six or eight months, I said, ‘This is ridiculous — I can’t just do nothing.’ ”

Less than a year after the accident, Swerdloff went back to Columbia. There were obstacles, of course, but one particular problem. Dentists rely on foot controls to use various devices — drills included — so Swerdloff was at a serious disadvantage. A classmate, Elihu Savad, soon solved the problem. Savad, who had an engineering background, built a unit Swerdloff could operate with his pinkie — literally. “Brilliant,” Swerdloff says.

In 1972, Swerdloff graduated from dental school — at the top of his class — then studied oral surgery at Mount Sinai Hospital in Elmhurst.

Swerdloff’s career was moving forward. Personal life was keeping pace.

On Aug. 28, 1969, Carol Roth and Mark Swerdloff were wed at a catering hall in Brooklyn called the Colonial Mansion, located on Bath Avenue.

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Questions about Carol’s emotions — did she have doubts about marriage after the accident? — earn only a quizzical look. Wholeness, she says, is not easily measured. The sweet, funny guy she met when they were kids at Abraham Lincoln High School in Brooklyn is the same person as before the accident.

“It makes no difference,” Carol Swerdloff says. “You know the song ‘I Never Promised You a Rose Garden’? I never expected that, just a good life.”

The Swerdloffs say they got that: a good life, and more.

They had two children, Michele, who lives in Woodbury and is executive director of a private Manhattan agency that aids special-needs children, and Rachel, of Manhattan, a director at an online wedding planning service. Around the house, Swerdloff’s daughters say, disabilities didn’t count.

“If we were eating and Dad said, ‘Where’s the ketchup?’ we’d say, ‘In the refrigerator,’ ” recalled Michele, 44, who is married to Gregg Riedel, 46, a vice president at Viacom, and has two children, Alexandra, 7, and William, 5. Swerdloff got no special treatment and didn’t want any, she says. “It’s the only way I’ve ever known him.”

The Swerdloffs were like anyone else. There were birthday parties and road trips — Dad’s wheelchair packed with the luggage — and Disney World vacations. “My feeling is that my father is not handicapped but ‘handicapable,’ ” said Rachel Swerdloff, 38. “My sister and I grew up believing that if you put your mind to something, you can do it.”

In 1975, Swerdloff was appointed to the faculty of the Stony Brook University School of Dental Medicine with a specialty in oral and maxillofacial surgery. Often working 50-60 hours a week, he slowed down to part time in 2007 and retired five years later. Along the way, Swerdloff received a Stony Brook President’s Award for Excellence in Teaching and a similar honor from the state university system.

To friends and colleagues, Swerdloff was a star.

“He’s a grinding guy who knows what should be done and does it,” said H. Barry Waldman, 80, a distinguished teaching professor who was hired in 1970 as the dental school’s first faculty member and remains on staff. “I feel sorry for students who don’t have him.”

Those who did count themselves lucky.

Mark Pancotto, 53, a Setauket dentist, studied with Swerdloff from 1984-88 and again as a resident in 1989. He said Swerdloff was demanding, detail-oriented and always available — even for midnight emergencies. “He never complained, never had an attitude,” Pancotto said. “Above and beyond — that’s how he taught, that’s how he practiced.”

With students, Swerdloff still earns an A-plus.

On a recent afternoon, Swerdloff, using hand controls, pulled his black 2011 Mercury Marquis onto a paved spot in front of Building Six at the Northport VA hospital, where he has treated patients and taught since 1976.

He scooted to the passenger seat on a transfer board and activated a roof carrier called the BraunAbility Chair Topper that delivered his wheelchair neatly to the ground. Swerdloff adjusted his slacks, rolled toward an entry tunnel and hurried down the hall for a meeting with dental residents.

There were four — chief resident Daniel Fleischman, 30; Adam Hoina, 29; Daria Liskin, 26; Christie Serigano, 26 — and each said the same: Swerdloff’s something else.

“He’s dedicated, enthusiastic, and loves teaching,” Liskin says. “His disability never gets in the way.”

That has always been the idea.

Aside from the accident that took his legs, Swerdloff has battled a number of health problems — kidney cancer, a neuromuscular disorder and an abdominal aortic aneurysm among them — but proclaims himself a happy man.

Sitting in his comfortable home before a wall of family photos, Swerdloff, a playful fellow who croons his voice mail greeting to the tune of the Mickey Mouse Club theme, grows teary for a moment.

“I’ve had a lot to overcome, but look at what I’ve been blessed with,” he says.

He leans a bit in his wheelchair and lowers one hand toward the floor and raises the other as if he were a scale. That is the story of his life, Swerdloff says. “Adversity,” he says, “is just a drop in the bucket.”