Charles Lee had been dealing with an excruciating toothache for days.

The pain made it hard to eat or sleep or focus on work. But Lee, 54, didn't have dental insurance. His job as a delivery truck driver offered only a supplemental policy that was too expensive. He feared he needed a root canal, which he knew could cost hundreds of dollars even with insurance.

The Department of Health in Pinellas County referred Lee to a free dental clinic in Clearwater, just blocks from his home, where a volunteer dentist found the cause of his issue and replaced two fillings for the price of a donation.

"I had nowhere to go. I had no affordable health care. I went into a Walgreens to see what they could do, and walked out with my tooth still killing me because they wanted $119 just to see me," said Lee, one of the 27 percent of U.S. adults ages 20 to 64 who, according to the Kaiser Family Foundation, are living with untreated dental issues.

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Most adults who don't have dental insurance end up in emergency rooms because of tooth or gum problems. The number of patients who go to the ER with dental-related issues surged from 1.1 million in 2000 to 2.1 million in 2010, and continues to rise, according to the American Dental Association. The organization says that up to 1.65 million ER visits a year could be better handled at dental clinics.

While the Affordable Care Act and low-income insurance programs like Medicare and Medicaid have improved Americans' access to health care, barriers still remain for adult dental care.

Local health departments, including in Pinellas, Hillsborough and Pasco counties, offer some low-income dental plans to residents who qualify. And children's dental care is covered nearly in full through Medicaid, the federal Children's Health Insurance Program and the ACA.

But Florida Medicaid plans for adults provide dental-related reimbursements only to participants who need emergency services to alleviate pain or infection or denture-related procedures, according the Agency for Health Care Administration.

At the Community Dental Clinic in Clearwater, dentists and hygienists convinced Charles Lee to come back for several follow up appointments, which helped get his dental care on track. And Lee didn't have to worry about how much he was paying for the continuing service.

"I was so impressed with what they did," he said. "The fact that a dentist would volunteer his time to help someone like me when he could be out making money, that really touched me."

"A lot of our patients come from underprivileged areas of Clearwater. When they get up out of the chair, they hug you. These are people who really appreciate it," said Dr. George Kostakis, who has run his own dental practice in Palm Harbor since 1989. He volunteers at the Community Dental Clinic and is among the nonprofit's board of directors.

The number of untreated dental cases in adults is highest among adults living at or below the federal poverty level, according to the Kaiser foundation.

"It's amazing how some people in the community clinic, they'll scoff at flossing. They laugh me off, but then I ask them, 'How much do you enjoy having teeth pulled?'" Kostakis said. "A lot of these people have never had any education into how to take care of their teeth. It's always been a reactive practice, not proactive. That's what we're trying to change."

In 2009, access to dental care was identified as the No. 1 social service need in Pinellas County by the Salvation Army, said Pamela Iusi, executive director of the clinic. In an effort to serve its community, the Salvation Army partnered with the Arc of Tampa Bay to launch the clinic, located at 1008 Woodlawn St. in Clearwater.

Today, it provides access to routine dental services for adults 18 and older who live in Largo and Tarpon Springs, and points in between. Patients are generally considered low-income, and must provide proof that they are uninsured or underinsured.

The clinic is so busy that in December it was already booked for appointments through April, Iusi said.

"If they don't qualify for dental insurance, oftentimes people don't have a lot of places to go other than the ER," she said. "And that can be incredibly expensive."

The need for adult dental care is so great that the St. Petersburg Free Clinic is raising money to build its own free dental clinic at the site of its existing health center on Fourth Street North this year.

At the Pinellas health department, dentists see emergency after emergency every day at their five county-wide locations, said Karen Hodge, the department's dental services manager.

Hodge said the goal is education, so they can stop treating so many emergencies.

"We're in the high schools offering sealants and fluoride," she said. "We're trying to break through this mindset that the dentist means pain."

Jim Brown, 50, stumbled into the Community Dental Clinic much like Lee, in pulsating pain from a cracked tooth and missing filling. He had lost his sales job in May and had no health insurance, let alone a dental policy.

"You expect things at a place that's free to be a little less-than-adequate," said Brown, who lives in Dunedin. "They gave me a full diagnosis. They came up with a treatment plan, got my teeth cleaned and had me come back for a periodontal cleaning."

Since he was unemployed, he couldn't pay much for the services, which he estimated would have cost "a few thousand" dollars at any other dentist.

"I hadn't seen a dentist in two years before that," Brown said. "I know I have to keep my dental work up more, maybe every four months. So I'm scheduled to keep coming back."

Contact Justine Griffin at jgriffin@tampabay.com or (727) 893-8467. Follow @SunBizGriffin.