When Dr. Jeffrey Burkes received the call, he assumed there had been a freak accident, a small private plane veering off course into a building. No matter: As the chief of forensic dentistry for the New York City medical examiner’s office, he had dashed to the site of every Big Apple disaster for more than two decades. His trip south to the World Trade Center this September Tuesday seemed like business as usual.

As Dr. Burkes got closer, though, he heard that another plane had hit the second tower. This was no accident. Then his wife squeezed a call through the jammed cellphone networks: The South Tower, she told him, had collapsed. Dr. Burkes was sure she meant the large radio tower atop the building; her insistence made him angry. “I had all this emotion in me, and she was telling me some story that the whole building fell down,” remembers Dr. Burkes, who in a quarter-century of disaster response had never seen more than a partial structural collapse. “How could the whole building fall down?”

The entire world, of course, soon knew how, and why. As Dr. Burkes later stared up at a 70-foot-high pile of twisted metal and debris stretching across 16 acres, the remains of 2,749 people — victims of the worst act of mass murder in American history — lay below. Ultimately, only 288 bodies would emerge intact. It would fall to Dr. Burkes and a team of 450 dentists and dental professionals from around the world to work through the gruesome aftermath, the 21,817 human remains pulled from the rubble, and provide vital closure to the victims’ families.

Ten years later, just as America itself still hasn’t fully recovered from 9/11, neither has Dr. Jeffrey Burkes.

IT WAS DURING another dark period for New York, the fiscal crisis of 1975 (symbolized by the famous Daily News front-page headline FORD TO CITY: DROP DEAD), that Dr. Burkes, a native New Yorker and an oral surgeon in private practice, began assisting New York City’s Office of the Chief Medical Examiner. He was named chief of forensic dentistry in 1980. His job entailed working every city disaster; in a typical year, he identified 250 victims of murders, fires and every other variety of urban mayhem. Until 9/11, he thought he had seen everything Gotham could dish out.

With 55,000 people working in the World Trade Center, the surrounding blocks should have been bustling. Instead, when Dr. Burkes arrived, they were merely eerie. He had a breathing mask in his kit, but the dust burned his eyes all the same. Shoes dotted the streets and sidewalks: The pavement was covered with talcum-like dust, making footing slippery, so people had abandoned their heels and office shoes to run. Fires burned here and there. Paper wafted about, filling every tree. “There were no desks or doorknobs. Anything dense like that burned up,” Dr. Burkes remembers. “There were ID tags. They weren’t solid enough to get destroyed.” With shoes and identification badges scattered haphazardly, it was as if people had just vaporized.

“Then I saw the pile,” Dr. Burkes says. “I’m looking right at it. I’m maybe 100 yards away.” What just hours earlier had been two immense glass-and-steel towers was now a debris field. “You don’t want to believe it. That’s how the mind works,” he continues. “My eyes were hurting and tearing. I said to myself, ‘I’m going to look south and clear my eyes; then I’m going to look again, and somebody better put that back.’ Nobody put it back.”

The initial hours of chaos eventually gave way to organized efforts. Rescue turned to recovery and identification of victims. That too was a round-the-clock activity, out of respect for the hundreds of first responders who died. “We don’t wait for them,” Dr. Burkes says. “They don’t wait for us.” For the next eight and a half months, the unit operated nonstop.

The work of moving and sifting through 1.7 million tons of debris started with a bucket brigade. It was dirty, draining, physical work. “Nobody who worked there called it Ground Zero. That was only TV,” Dr. Burkes says. “Anyone who was there called it the Pile. Once it got to street level and down, it became the Pit.”

Dr. Burkes didn’t see footage of the towers collapsing for two weeks; he was either working or sleeping and didn’t have time to watch TV. Many people gave in to exhaustion for a few hours on a pew in St. Paul’s Chapel, adjacent to the World Trade Center and miraculously undamaged in the attacks. Meals were often a quick bite from Sal’s Café — a cafeteria in a temporary trailer run by the Salvation Army for those working at the site.

Dr. Burkes quickly assembled the 40 New York dentists who made up his mass-disaster team. Given the scale of the atrocity, they had to recruit help and assume oversight roles. As the vice president of the American Academy of Forensic Sciences and the president of the American Academy of Forensic Odontology, Dr. Burkes was in a position to call for experienced volunteers. “You saw the worst in humanity — people flying planes into buildings and killing innocent people,” he says. “And you saw the best in humanity. So many people said, ‘Whatever you need’ or ‘I’m going to come help.’ ”

DENTISTS, ALMOST ALL of whom do forensic work on the side as consultants or volunteers, responded in droves. Dr. Burkes got support from the military, which flew dentists in before commercial flights had resumed. Some stayed a few days or weeks. Some set aside their practices and stayed for months. (They came as volunteers, though most were eventually able to draw payment through federal emergency funds.)

“When a disaster happens, everyone is pumped up to help,” Dr. Burkes says. That willingness to assist often leads people to try to do things they can’t (or shouldn’t), so he set up shifts. “How good are you working 70 hours straight?” he asks. “You start to see double. You can’t work like that.” Shifts were eight hours for the teams, but 12 hours for captains to ensure clear communication and leadership across shifts.

As recently as the 1990s, Dr. Burkes says, few dental schools offered formal forensic-dentistry training. Most dentists gained such experience by volunteering or consulting with local medical examiners’ or coroners’ offices. Interest was confined to a small number of people and a few professional associations. “When I started, people didn’t know what ‘forensic’ was,” Dr. Burkes says. “Now, with CSI and all the other forensic shows, there is tremendous interest in the field.”

The medical examiner’s office created comprehensive profiles of every victim by gathering data through seven-page questionnaires. The most offhand details — a Mickey Mouse tattoo, an artificial hip — thereby became a means of identification. In recent decades, DNA has become increasingly helpful in this regard. To this day, some 9,000 partial 9/11 remains are still unidentified, but there are occasional breakthroughs. This August, for example, DNA technology produced a match of a finger bone. That single bone enabled one family, at long last, to hold a traditional religious funeral.

Dental identifications offered speed and certainty, especially in the early going. The work involved X-raying and charting all dental remains, as well as gathering antemortem charts for all possible victims. “It was fortunate that this happened at a time in my career when I had seen almost every type of disaster,” says Dr. Burkes, who is now 63. He was able to set up a system that could adapt to an event the scope of whose horror was so vast that remains eventually filled 16 refrigerated trailers.

IN 1975, WITH LITTLE MORE than a dental-school forensics lecture as background, Dr. Burkes assisted Dr. Lowell Levine with identifications following the wreck of Eastern Airlines flight 66, which crashed as it approached JFK Airport that June. The experience made him a firm believer in learning through doing.

“This was a great teaching experience for dentists who had only book knowledge or a course in forensics,” Dr. Burkes says. He recognized, too, that some of his experience as an oral surgeon might not be perfectly suited to all forensic tasks. “The methods used in forensic dentistry draw on what general dentists do on a daily basis,” he says. “Taking an impression, doing models.”

At the same time, working with human remains takes a toll. For some, that happens immediately. “They find out they really can’t take this type of work,” Dr. Burkes says. “But then it’s too late. You saw it already. You can’t erase it. We don’t have the Men in Black memory-wipe tool. That would be nice. Instead, you have to go to counseling. And sometimes you’re never OK.”

It became pretty much impossible to keep the process fully clinical. Families began delivering photographs and toothbrushes or hair samples to the dental team. Knowing the victims’ faces, meeting grieving families and hearing personal stories while working with thousands of remains proved a crushing burden. When Dr. Burkes knew the victims personally — a half-dozen of his friends died that day — he left the room during final identification. Perhaps his closest confidant to perish was William M. Feehan, a former New York City fire commissioner who was still serving the department, at 71, as first deputy. Feehan was the highest-ranking fire official killed at the site. “He was one of the great guys,” Dr. Burkes says. “I looked up to him. He was my hero.”

Dr. Dorline Bosboom, one of Dr. Burkes’s lieutenants, remembers contacting a dentist for clarification about a chart being used with a possible match. As Dr. Bosboom talked, she realized that the dentist she was speaking to was the victim’s sister. She sighs heavily at the recollection. “You can’t do your job if you’re emotionally involved,” she says.

Remains at the site were scattered over a large area. With so many fragments and no clear origin point to organize around, computers provided invaluable support. The dental team used WinID, a database system designed to suggest possible matches between all antemortem and postmortem charts and radiographs. Dr. Burkes explains: “If you find a left lower molar with a silver filling and a decayed tooth next to it, the computer comes back with maybe 75 people. Now someone has to look at the antemortem X-rays of the 75 people to make a match.”

To avoid errors, three dentists were required to concur with each identification. In addition, the team employed multiple ID modes whenever possible. Of 1,632 victims identified, 596 matches used dental means, but just 52 relied solely on dental identification. Families’ wishes, naturally, were respected as much as possible. Some simply accepted their loss, not wanting wounds to be reopened months or even years later. They were given the right not to be told when ID’s were made. Some declined to provide records. Some were unable to locate any. That, Dr. Burkes says, is all part of the challenge and complexity of the work.

THE MOST INTENSE PERIOD was over by the end of 2002. In the years since, additional identification efforts have typically stemmed from new discoveries. “People don’t realize that things were falling from such a height, and the forces weren’t just down but out,” Dr. Burkes says. “One body was found as far away as the East River.” Even now, a decade on, debris and remains are occasionally found on rooftops some distance from the site.

In the wake of his recovery work, Dr. Burkes found himself treated as something of a hero. He and others received commendations, the occasional police escort and a reserved spot for the Thanksgiving Day parade. These few small perks, though, couldn’t possibly offset the toll 9/11 took on Dr. Burkes. After having experienced some personal troubles, he has been on leave from the medical examiner’s office since 2006.

Regardless of the difficulties of the ensuing years, he still devotes considerable time to forensic odontology; he’s a member of several associations and sometimes testifies in court cases as an expert witness. His connection with 9/11, of course, will endure forever. In late September, a few days after the commemoration of the tenth anniversary of the attacks, I accompany him as he visits the memorial, recently opened to the public, for the first time.

As a rainy afternoon gives way to early-evening sun, Dr. Burkes proudly attaches to his jacket the security pass that had given him access to the Pile those first exhausting months. Looking around, he thinks about the many families who, a decade later, still lack the certainty that comes with a forensic confirmation. To some degree, he feels that his job remains unfinished. “It rips your heart out,” he says. “It’s a terrible, terrible thing, so many children growing up without parents.”

The memorial consists of two sunken reflecting pools, representing the void left by the towers. The names of the dead are carved into the pools’ bronze walls. At one of the kiosks that enables people to locate the names of the deceased, Dr. Burkes types WILLIAM FEEHAN. The fire commissioner’s grinning visage appears on the screen.

“He always had a smile and a kind word,” Dr. Burkes says. “He was so unassuming.” Then he notices that Feehan was born September 29, 1929 — by chance, Dr. Burkes is paying tribute to his hero on what would have been his eighty-second birthday. Filled with emotion, he pauses. After so much horror, it seems, solace is often found in small wonders.

Ted O’Callahan, who has written for the New York Times and the Washington Post, last wrote for Incisal Edge about Hall of Fame dentist Dr. John Siegal Sr.

Matthew Furman is a freelance photographer based in New York.

Forensic Dentistry Solves A 179-Year Murder Mystery

IN THE SUMMER of 1832, 57 young Irishmen were hired right off the Philadelphia docks — railroad work as the first step toward the American Dream. Eight weeks later, they were all dead: Some succumbed to cholera, while those who sought help or tried to leave, it is believed, were murdered to prevent the outbreak from spreading. All the bodies were buried, most of them in an unmarked mass grave about 30 miles west of Philadelphia, in a stretch known as Duffy’s Cut.

Nearly 180 years later, forensic dentistry is helping solve this mystery. “The story needed to be told,” says Dr. Matt Patterson (right), a dentist in private practice in Lancaster, Pennsylvania. “America did them wrong. We need to fix that as best we can.” Trained in forensic odontology at the Armed Forces Institute of Pathology, Dr. Patterson volunteered his expertise when he heard about the effort to figure out exactly what had happened.

Duffy’s Cut was the hardest mile of the Pennsylvania and Columbia railroad. The Irish laborers did backbreaking work in brutal summer heat, reshaping the land with nothing more than shovels, pickaxes and hand carts while living in crude shanties beside the work site.

Information about their deaths was suppressed; their families never learned what happened. The immigrants had become little more than a ghost story: Growing up, Frank and Bill Watson heard a tale from their grandfather, who had worked for the railroad, that some nights the dead Irishmen could be seen dancing near that stretch of track.

Years later, the Watsons discovered evidence of a cover-up in railroad papers found among their grandfather’s possessions. Their sleuthing led to an excavation, the Duffy’s Cut Project, and in 2009 the Watsons unearthed a skeleton that showed signs of a traumatic death.

Enter Dr. Patterson, whose examination revealed a missing upper right first molar. The tooth hadn’t been removed; it had never been there in the first place. “That’s an exceptionally rare defect,” Dr. Patterson says. “In 26 years of doing this, I’ve never seen it in the journals, or in real life.” Using that clue and the rolls of workers’ names, investigators were able to contact the men’s descendents in Ireland. Only one family had the missing-molar trait, leading to a presumptive identification of John Ruddy, who was a teenager when he died. (DNA confirmation is pending.)

As he works on identifying six other bodies, and the Watsons negotiate with Amtrak for access to the likely location of the mass grave, Dr. Patterson is doing right by these pioneers. “It’s incredibly moving to be part of this,” he says. “We felt a kinship with the men. In the military, we never left a man behind. Ideally, we will recover everyone, separate the commingled remains, identify them, repatriate those whose families want that — and bury the others in consecrated ground.”