The bone had been cleaned, cut, pulverized, chemically treated and incubated five times before it produced enough DNA for a positive identification.

The first two attempts were nonstarters.

Forensic scientists with the Bode Technology Group in Virginia, where New York City sent many unidentified human remains in the aftermath of the Sept. 11, 2001, terror attacks on the World Trade Center, failed twice in 2002 to extract clear, liquid DNA that could generate a profile.

The bone, dehydrated and vacuum-sealed in a white package marked with an American flag and bar codes, came back to New York City’s Office of Chief Medical Examiner.

About 10 years ago, newly equipped with more advanced technology, the medical examiner’s Missing Persons Unit began trying again. And again.

Then, in July, a breakthrough: a complete DNA profile and a conclusive link to Scott Michael Johnson, a 26-year-old Montclair resident who worked on the 89th floor of the south tower as a securities analyst at Keefe, Bruyette & Woods.

“It was exhilarating,” said criminalist Carl Gajewski, a member of the unit.

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