Their idea was simple: Use chewing gum to change the world. The team of five friends from the University of Pennsylvania - none older than 23 - developed Sweet Bites, chewing gum made with a sugar substitute called xylitol that fights tooth decay and that could improve oral health in the world's poorest areas.

The culmination of months of hard work and countless all-nighters played out late last month on a stage where, earlier in the day, President Obama had stood. In their nicest suits and a fancy dress borrowed from one of their mothers, they addressed an audience including a Nobel laureate and a CNN anchor, and had their words live-streamed all over the world.

They were competing for the Hult Prize, $1 million in seed funding, for the best proposal to ease chronic illness in urban slums. This year, 11,000 teams applied, making it the world's largest student competition for social good.

The Sweet Bites team from Penn was among the last six left standing. They had made it to the award dinner, where the 42d U.S. president, Bill Clinton, who sets the topic each year, was to announce the winner.

It's not every 22-year-old who scores an invite to the Clinton Global Initiative annual meeting, a premier global meet-up of social entrepreneurs in New York. Under the bright lights, a young man on a competing team, who had surely prepped rigorously for this moment, fainted onstage.

The Sweet Bites team anxiously waited for news about him - over the many months of the competition, they had gotten to know this competitor and considered him a friend. "He is in the hospital with his uncle, doing fine," Clinton reported.

"You in so many ways represent the future," he told all the finalists.

But there was only one check, and the five judges, who included CNN's Sanjay Gupta and Nobel-winning economist Muhammad Yunus, would have to decide.

The idea for Sweet Bites crystallized in Philadelphia. Cofounder Morgan Snyder had come back from nine months in Bangalore, India, where she worked at schools in low-income communities, and had noticed many of the children wouldn't smile - not because they were shy, but because of their oral health problems.

When she returned to Penn (where I was classmates with members of the team), she told her friends about the shocking state of oral health in Indian slums. One friend, Spencer Penn, was an avid gum-chewer who heard that gum with xylitol was proven to prevent cavities.

They were joined by Josh Tycko, Eric Kauderer-Abrams, and Thoba Grenville-Grey to found Sweet Bites, a company that plans to sell xylitol gum - for up to 1.6 U.S. pennies per piece - an idea so ingenious it was named No. 1 of "11 Simple Inventions That Could Change the World" by the Huffington Post.

An early meeting with Ezekiel Emanuel, chair of medical ethics and health policy at Penn, proved game-changing.

Emanuel, by coincidence, had lauded the bacteria-killing abilities of xylitol gum in a 2012 New York Times blog post. "He told us when it comes to health care, free is not cheap enough," recalls Penn.

Therein lies the simple brilliance of Sweet Bites; it is care that doesn't require a change of behavior because everyone can chew gum.

Their adviser, Ian MacMillan, director of the Sol C. Snider Entrepreneurial Research Center at the Wharton School, helped get the team university funding and is the author of The Social Entrepreneur's Playbook, which the team calls its bible, and which would consult it when obstacles cropped up. There were plenty.

Like when the team arrived in Bangalore to launch its pilot program and learned that five boxes with 25,000 pieces of gum were held up in Indian customs.

Luckily, they had stuffed their pockets and carry-on bags with enough gum to last their monthlong visit. Still, it was a relief when the boxes finally appeared on their last day in India.

For the Sweet Bites team, the summer was a blur of more trips to India, hard work at the intensive Hult Prize Accelerator, where the six finalist teams refined their ideas in close quarters and looked for crowdsourced funding. They exceeded their target, raising nearly $17,000 from more than 200 donors, mostly in denominations between $25 and $100.

Another stroke of good fortune came from a cold call to Bill Goodwin, founder of the Goodwin Design Group, in Wallingford, Delaware County, which did the dramatic redesign of Bazooka bubble gum. Goodwin was enthusiastic about the project, and his team gave the Sweet Bites packaging a much-needed makeover. "We found it very inspiring to work with people in his team," said Kauderer-Abrams. "They probably worked as hard as we did leading up to the presentation to get all this beautiful branding and everything done in time."

They felt strong going in to the competition, and their presentation, the product of hundreds of run-throughs, went without a hitch.

So it came as a surprise when Clinton announced that the $1 million prize was going to NanoHealth, a team from the Indian School of Business that envisioned a network of health workers equipped with an innovative diagnostic tool to provide on-the-go diagnosis and treatment for slum-dwellers.

The Sweet Bites team was surprised, but not bitter. "It's kind of the opposite of Sweet Bites in a lot of ways," Penn said afterward, adding, "Obviously, we respect the decision of the judges."

The next day at a meet-and-greet, the team got to talk with Clinton. They also tried to get him to sign an excuse note for all the late school assignments they had racked up while working toward the Hult Prize. ("He was down to sign it, but his handlers weren't," Penn said.) Even better, he asked for samples of the gum to take back to the Clinton Foundation.

The team plans to catch up on school and hit the drawing board. They promise this isn't the last we will hear of Sweet Bites.