Danbury — The prospect of dental work, much less waiting outside overnight for it, doesn’t tend to put people in a good mood. Then there’s Eileen Pedevillano.

“I’m so appreciative that they’re doing this,” she said Friday morning outside the fifth annual Connecticut Mission of Mercy, a free dental clinic. “I could never complain.”

Oxygen in tow, Pedevillano had arrived to get in line around 3 a.m. She has lung disease and said she needs to take care of some dental problems before she qualifies for medical procedures, including the lung transplant she expects to need one day. She has medical insurance through Medicare, but it doesn’t cover dentistry, and the Seymour woman said she doesn’t have the finances to take care of all the dental work she needs.

So Pedevillano, like hundreds of other Connecticut residents, has made the once-a-year Mission of Mercy her regular source of dental care. Every year, she spends a few hours in line outside to snag a spot at the clinic, which takes patients on a first-come, first-served basis. Some years, the line has been so long the clinic reached capacity before opening.

The line didn’t fill up quite as fast at this year’s clinic, which is being held from 6 a.m. to about 6 p.m., Friday and Saturday, at Western Connecticut State University’s O’Neill Center in Danbury. Six-hundred forty people had arrived by shortly after 7 a.m. Friday, and the clinic reached capacity for the day — 1,100 people — around 1 p.m. It drew about 1,600 volunteers.

Pedevillano’s wristband identified her as number 246 in line, although she actually arrived 247^th. Tom Loftus, the real number 246, switched places after learning that 246 was Pedevillano’s lucky number. He, too, has become a regular; this was his third clinic, so he knew to come around 3 a.m. and to expect to spend the early morning hours talking and “making friends.” The American Red Cross set up overnight to provide coffee, tea and hot chocolate, and the United Way provided blankets. Around 7 a.m., a volunteer walked through the line passing out Egg McMuffins.

Loftus, 37, of Waterbury, works as a carpenter and has medical insurance through his job, but no dental coverage.

It’s a relatively common problem in Connecticut, where close to 400,000 people don’t have health care coverage and the number without dental insurance is far higher; experts have placed it at 600,000 to 1 million.

Even people with dental coverage can struggle to get treated, particularly adults in Medicaid, which pays rates so low few dentists will accept many — or any — patients with it. And many private dental insurance plans limit coverage to $1,000 or $1,500, leaving people who need extensive work to face significant out-of-pocket costs.

This year’s Mission of Mercy fell on the second anniversary of the federal health reform law, during a week many politicians and supporters used to highlight the ways the act would expand health care coverage and make life easier for people with insurance, including by limiting their out-of-pocket medical expenses. The law includes some new requirements for dental coverage for children. But it isn’t expected to expand access to dental care for adults, or to make coverage more affordable.

Mission of Mercy organizers say the clinic can’t be a substitute for broader changes in the health care system.

But for now, the Connecticut Mission of Mercy has become the closest thing there is to a solution, at least for people like Pedevillano and Loftus.

Dr. Suzanne Lagarde, a gastroenterologist and board president of Project Access New Haven, which coordinates free medical care for uninsured patients, spent Friday overseeing the medical triage section of the dental clinic, her fourth year volunteering. Sometimes, she said, she envies dental care.

“You can take care of an acute problem” in this kind of setting, she said, in a way you can’t with a chronic medical problem like high blood pressure.

“We could do better as a society and as a country, but I’m still very proud of what we do in Connecticut,” she said.

Dr. Robert Schreibman, a Glastonbury pediatric dentist who co-chairs the Connecticut Mission of Mercy, said about 200 to 300 people now use the clinic as their regular source of dental care.

“It’s become a dental home,” he said.

There are also regular volunteers, like Robbin Hamilton of West Haven, who learned about the clinic from her dentist and has helped out at the past three clinics. On Friday, she served as an escort, taking patients from the registration area to medical triage, where nurses and medical students took their medical histories. In the first couple hours, she’d already escorted about 70 patients, taking turns with a handful of other volunteers.

But she skipped the order when she spotted Henry Ponticello at the registration desk.

“He’s my favorite patient!” she exclaimed as she approached and hugged him.

They know each other from their lives outside the clinic — Hamilton works as a patient account representative at Yale-New Haven Hospital, and Ponticello is a patient; he credits her with getting a drug company to pay for expensive experimental medication that helped treat his neuromuscular disorder. When he comes for dental care at the Mission of Mercy clinics, he and Hamilton make a point of trying to find each other.

Ponticello, 69, lives in Newtown and is retired after a career in sales. He has Medicare, leaving him without dental coverage. He arrived around 3:30 a.m. Before he started going to the Mission of Mercy clinics, he hadn’t seen a dentist in “a while.”

Now, he said, “This is where I go.”

For all the regulars, the clinic, which is held in a different part of the state each year, still draws hundreds of new patients. This year, Jessica DeVries was one. She and her 9-year-old son arrived on Thursday around 1 p.m., becoming the first in line.

“I’m just so grateful,” she said 18 hours later as she sat in a dental chair set up in one of several rows on the gym floor. She raved about Dr. Stephen Moran and dental assistant Angela Branford, who had fixed a broken front tooth and a back tooth.

DeVries said her front tooth broke when she was 15. She’d had a metal cover put on the back tooth when she was 10 or 11. She’s now 40.

The teeth gave her pain on and off. “But you just kind of move on to other things,” she said. Her money gets spent on her family, not her teeth.

DeVries still had some work to get done before she left. But she was already thinking about the 2013 Mission of Mercy.

“My husband will be at the next one,” she said.

By 8:30 a.m., Pedevillano, number 246 in line, was in the waiting area for oral surgery. She’d learned she needed an extraction, and would have to come back Saturday to get more work done.

“I’m just happy it’s getting done,” she said.

Then you’ll be perfect, the volunteer escort with her said.

Oh please, Pedevillano scoffed; her teeth would still be far from perfect.

“But better,” she said.