The first two people in line arrived within 10 minutes of each other Friday evening, ready to sleep on the sidewalk for free dental care Saturday morning at a high school in Laurel.

Twelve hours later, one woman was reclining in a dentist’s chair, getting a new tooth made of a synthetic composite. The other was heading home: The temporary clinic, which served 700 people Friday and Saturday, was unable to provide the treatment she needed, which involved multiple crowns and an abscess, without a specialized lab.

About 300 other adults were turned away over two days because of the overwhelming demand for dental care at the Mid-Maryland Mission of Mercy clinic. The clinic, at St. Vincent Pallotti High School, was sponsored by Catholic Charities of the Archdiocese of Washington and the Maryland Office of Oral Health.

Many of those who waited in long lines at the clinic said they couldn’t afford the high price of dental care. Even those who had insurance said rising out-of-pocket costs made it unaffordable for them to have their teeth cleaned, cavities filled or root canals performed.

More than 400 volunteers — about half of them dentists, hygienists, oral surgeons and others in the field — provided more than $750,000 worth of care over the two days, according to Deacon Jim Nalls of Catholic Charities. The work ranged from basic cleanings to root canals and wisdom teeth extractions, Nalls said.

Yasmin Bellavigna, 40, of Laurel, the first person in line for Saturday’s session, said that a cap fell off a tooth a year ago after a root canal and that even with dental insurance, she couldn’t afford to replace it. So the stay-at-home mother of two girls brought a yoga mat and blankets at 8 p.m. Friday and watched as the line quickly curled around the block.

Cathi Stallings, 55, a social worker from Falls Church, joined her about 8:10 p.m., hoping to have several procedures done, including several crowns. She said her insurance wouldn’t cover the cost of the crowns, about $2,000 each.

“There’s not enough to cover everything I need,” Stallings said.

Although she didn’t receive the treatment she needed, Stallings said, the “eye-opening” trip was worth it. “It made me realize how many people are in the same boat,” she said.

Fayola Melville, 28, of District Heights said that she normally goes to a dentist for treatment but that a necessary extraction proved too expensive, even with her insurance. She was told that she would have to pay $2,000 for an oral surgeon to remove the tooth, she said, and that her insurance would cover about 25 percent.

“It’s ridiculous,” she said.

The clinic’s timing was perfect for Joyce Neal, 53, a motor coach driver from Rockville. A filling broke Friday as she snacked on sunflower seeds while driving on the Capital Beltway. Neal hadn’t planned on going to the clinic, she said, but a previous visit to a dentist who wanted to charge $2,700 for a filling motivated her to be No. 13 in line Friday night.

“It’s terrible,” she said. “They should adjust it to low-income people.”

Neal had three fillings and two extractions done Saturday.

There are programs to give children access to dental care, but adults are left with very few options, and many avoid trips to the dentist until it’s too late, said Frank McLaughlin, executive director of the Maryland State Dental Association.

“Adults are not being taken care of,” McLaughlin said. So clinics such as the one in Laurel try to fill in the gaps — and its recipients are appreciative, often murmuring their thanks through a mouthful of gauze.

On Saturday, patients waited in lines for hours throughout the high school. Check-in was in the main lobby; X-ray was in a classroom; and procedures such as cleanings, restorations and extractions were done in a gym that hummed with the whirs and whines of drills and other dental instruments.

Martha Murphy, a Gaithersburg dentist, basically built a tooth out of a synthetic composite for Bellavigna and filled a cavity, an hour of work that would have cost about $800 in her office.

“God bless you for doing this,” Bellavigna said to Murphy after the new tooth was finished. “I have a tooth again! I’m so thankful. Oh my gosh, it’s so nice to have a tooth there.”

For Brianna Wilson, it was time to take a few teeth out.

The 25-year-old administrative assistant from Davidsonville doesn’t have dental insurance, and she needed to have her wisdom teeth removed. The University of Maryland School of Dentistry told her the extraction of all four would cost $1,000 — money she doesn’t have, she said.

Hearing about the clinic on the news was an answer to her prayers, she said.

Alan Berne, a retired dentist from Ellicott City, advised her to stock up on milkshakes as she recovers — and to slurp them without a straw.

In his 39-year career, Berne said working at clinics has been the most rewarding part of his vocation. In three hours Saturday, he took out 60 teeth from 10 patients.

“They’re just happy to have somewhere to go to get care,” he said.

More than 16 hours, a new tooth and a cleaner mouth later, a tired and hungry — but very happy — Bellavigna left the clinic.

“It’s such a stress reliever,” she said. “It was worth every minute. And more.”