With more than 16 million low-income U.S. children on Medicaid not receiving dental care -- or even a routine exam -- in 2009, according to the Pew Center on the States, dentists and ERs say they are treating very young patients with teeth blackened from decay and bacteria and multiple cavities.
"I see it in their eyes before they tell me it's that way," Dr. Gregory Folse told ABC News. "We are able to intervene and take the pain away from their teeth and it brings the spark back. And that's my goal."
For more on the "Hidden America" series, watch "World News with Diane Sawyer" Tuesday at 6:30 p.m. ET.
Folse's Outreach Dentistry mobile clinic travels to schools around Louisiana, filling cavities and teaching children and parents about the importance of oral hygiene.
In 2007, Congress held a hearing on the issue of children's dental health after Deamonte Driver, a 12-year-old Maryland boy, died when a tooth infection spread to his brain. His mother, Alyce Driver, had been unable to find a dentist to treat him on Medicaid and could not afford to pay out of pocket.
At the time, Leslie Norwalk, then-acting administrator for the Centers for Medicare and Medicaid Services, called his death "a failure on many levels."
And although she said that these types of dental services were covered, many dentists said that Medicaid reimbursement rates are too low.
A study published in May 2011 demonstrated that despite efforts to boost the number of patients and providers in the Medicaid system, low-income families still had limited access to dental care -- except when they were able to pay cash.
The state of Florida got an F in children's dental health in a 2011 report from the Pew Center on the States. In 2009, according to Pew, only 25.7 percent of Florida children on Medicaid saw a dentist.
"The Medicaid rates are so low that dentists are not willing to participate in the Medicaid program," said Dr. Frank Catalanotto of the University of Florida, Gainesville, Community Dentistry. "You can't blame the dentists, really, because the cost of delivering the service is more than the reimbursement they receive."
Florida has some of the lowest rates. Ten pediatric dentists in four counties said they would not accept Medicaid -- even for a child whose face hurt. And more than half of Florida's counties -- 36 -- do not have one pediatric dentist who takes Medicaid, according to Pew.
Dentists say that ignoring teeth can mean life or death. An infection can kill or promote heart disease, stroke, diabetes and osteoporosis. Children who do not receive dental care can suffer root canals and extractions before they reach 10 years old.
At the Caridad Center in Boynton Beach, Fla., Falguni Patel, a first-year resident in pediatric dentistry, said it made her sad that there were certain groups of children who suffered more than others.
"People think just because you have insurance that you're going to have access to care -- which is not the whole story," she said. "They're very few pediatric dentists that accept Medicaid in this area, so these children have nowhere to go even if they do have insurance. ... It's a big problem."