WASHINGTON — Alice Wu said she felt like a winner even before finding out she and her partners finished fifth in the Siemens Competition in Math, Science & Technology’s team category on Tuesday, recipients of a $20,000 scholarship award.

Standing alongside some of the country’s brightest students and gaining insight from an academic all-star panel of judges were highlights of the prestigious contest’s national finals, said the senior at Half Hollow Hills High School West in Dix Hills.

“I learned a lot more about science in general because the competitors have amazing projects,” said Wu, 17, wearing her finalist medal around her neck. “It shows me science, the opportunities are endless.”

She and her two teammates tackled gum disease, which affects nearly half of all adults, by finding ways to regenerate bone and teeth through altering the surface on which the cells grow. The dental-pulp stem cells they used came from extracted wisdom teeth, so they avoided ethical dilemmas in the use of stem cells.

Rows of proud parents and mentors in The George Washington University’s Jack Morton Auditorium watched as members of the six teams and the six individual finalists gathered on a poinsettia-adorned stage for the awards announcement.

Wu, 17, was the only student from a Long Island school in the national finals. She met her teammates — Katherine Cao of Mequon, Wisconsin, and William Hu of Saratoga, California, both seniors and 17 — in the Garcia Summer Program at Stony Brook University. The three of them stood, grinning, behind a giant fake check to represent the $20,000 they share in prize money.

Wu said the trio had quickly clicked over a desire to apply materials science — that is, the study of optimizing use of material — to medicine.

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“Our senses of humor aligned, our values as academics. I knew I wanted to work with people I genuinely enjoy being around,” she said. “It’s important to laugh in the lab.”

The competition’s $100,000 scholarship grand-prize winners were individual competitor Vineet Edupuganti, 17, of Portland, Oregon, who developed a biodegradable battery, and the team of twin sisters Adhya and Shriya Beesam, 16, of Richardson, Texas, who were motivated by their uncle’s illness to build a predictive model for diagnosing schizophrenia.

The Siemens national finalists were treated to a weekend of activities targeted to their intellectual interests, such as building and battling robots and using an app to learn about the Lincoln Memorial.

On Monday, they got down to business, giving presentations and answering questions from a 13-judge panel. Wu and her teammates were prepared with a 15-page Google document with every question they believed they could face. After working last summer on the project, they finished it through late-night Skype sessions.

Wu said her heart was racing as she stood on the stage waiting for results. More nerve-wracking than presenting to the judges, she said, was knowing that her classmates on Long Island were watching a live-stream of the awards in the Half Hollow Hills West school library. Along with her science research efforts, she captains the cross country, winter track and badminton teams and works with local programs that promote leadership among girls.

Wu’s mother, Sharry Wang, is a chemical engineer whose husband, Qifei Wu, works in research and development at a pharmaceutical company. Her daughter, she said, is determined to give something to the country to which her parents came from China when they were 28. And the Siemens competition was an outlet for Wu’s ambitions.

“Siemens gave them a chance to do this kind of research and open their eyes to see the outside world,” Wang said.

The team was mentored by Stony Brook University’s Miriam Rafailovich, distinguished professor of materials science & engineering; Marcia Simon, professor and director for graduate studies at the School of Dental Medicine’s Department of Oral Biology and Pathology; and Adriana Pinkas-Sarafova, Garcia Summer Program coordinator in the Department of Materials Science and Chemical Engineering.

Rafailovich said the team’s findings, which must be tested in extended studies, create potential for “the development of a new therapy to use live cells to make a real tooth.”

The regenerated tooth is superior to an artificial one because “a real tooth integrates into the homeostasis of the entire mouth,” she said. “When you put in an artificial implant, you have tons of problems — you have rejection, the bone can contract . . . A living tooth adapts to its environment.”

Michael Lake, academic research director at Wu’s school, was one of the first to congratulate her after the announcement.

“She’s a hard worker . . . engaged, enthusiastic,” Lake said. “Kids like that are easy to work with. Whatever they choose to do in life, they’ll do with tremendous fervor and zeal.”

Wu said she’s interested in computer science as well as biomedical engineering. She hopes to be accepted for admission at Yale University and to continue to do research in college.

“I’ve never felt as much sense of accomplishment as a successful experiment,” she said.

Wu was among 69 Long Island students named Siemens regional semifinalists this year. Ten from Long Island school systems next achieved the designation of regional finalist and presented their projects to judges at Siemens-designated universities at that level.

This year’s participants initially totaled more than 2,000 students nationwide, who submitted 1,600-plus projects in areas of computer science, physics, chemistry, mathematics, materials science, environmental science, biochemistry, biology and engineering.

Last year, Manhasset High School seniors Kimberly Te and Christine Yoo, both 17 at the time, won the $100,000 grand prize in the team competition. They created a device that uses naturally occurring bacteria to clean up oil spills and generate energy in that process for use in Third World countries.

The Siemens Competition, launched in 1999 by the Siemens Foundation and administered by Discovery Education, seeks to recognize the nation’s most promising young scientists, engineers and mathematicians.

With Scott Eidler