J&D Dental, a small practice in downtown Minneapolis, thought it might pick up a few new patients by offering a deal: a dental exam, X-rays and cleaning for $49 instead of the usual $231.

It did -- 768 in a single day.

J&D offered the deal this week on Groupon, a hugely popular website that offers deep discounts if a minimum number of people buy. Groupon is most commonly associated with restaurant deals, but J&D is one of a growing number of health care providers using it to reach new customers who have limited or no insurance.

Don't expect to see discounted MRIs on offer -- at least not yet. But dental, cosmetic, chiropractic and other procedures usually paid for out-of-pocket have sold very well, Groupon spokeswoman Julie Mossler said.

The J&D deal is valid for a year. "It sounds like the phones are ringing off the hook" with people trying to make an appointment, said Dr. Jennifer DeChant, one of two dentists at the practice.

Groupon, which started two years ago in Chicago, has expanded to 95 markets in the United States and Canada. It was recently anointed the fastest-growing company in Web history by Forbes magazine. In the Twin Cities, it has spawned local competitors such as Dealstork and Crowd Cut, where discounted spider vein treatments and Botox sessions were on offer this week.

A deal must attract a sufficiently large group of buyers -- the name Groupon is "group" and "coupon" combined -- to trigger a group discount. The concept appeals simultaneously to people's love of deals, their herd mentality and a sense of urgency. Each deal is available for only one day.

In the Twin Cities, 340,000 people receive daily e-mails from Groupon. A recent deal for laser hair removal -- $99 for three sessions, or roughly 80 percent off -- had more than 900 takers.

Groupon splits revenue 50-50 with the featured business. The business may initially lose money, but the hope is that it will gain new customers who return again and again.

DeChant was inspired by a dentist friend in Woodbury who netted more than 300 new patients through Groupon.

She figured there were lots of unemployed people out there who'd lost their dental insurance and were putting off seeing a dentist. Maybe, she thought, this would get them in the door and they'd keep coming back after they found employment.

Wednesday morning, an e-mail blast on the J&D deal went out between 5 and 7 a.m. The tipping point, or minimum number of buyers needed, was 40. The deal "tipped" at 7:16 a.m. In between seeing patients, DeChant and her partner, Dr. Jennifer Herbert, watched the number climb during the day. Said DeChant:

"We looked at each other and thought 'Oh my God, I hope they don't all want to come in the next few weeks.'"

Chen May Yee • 612-673-7434