Inside, just beyond the double-doors graced with a “Fear the Turtle” banner, a reference to the university's mascot, what unfolded was the opposite of a typical American dental visit, with its gentle small-talk and freebie toothbrushes. Here, tired-looking patients sat clustered in groups behind black cloth dividers, their dentists racing by with barely enough time to look up. A seemingly disoriented woman ambled toward me, her mouth stuffed with bloody gauze.

Under the bright gym lights, the patients were nearly elbow to elbow as their doctors worked. The event saw 1,200 patients this year, up from 700 last year. Not everyone could be seen on Friday; about 1,000 were turned away and told to try again the next day.

A tiny 3D printer stamped out new, fake teeth as their future owners waited nearby. In the middle of it all, a choir sang hymns on an elevated stage, lending the whole thing the air of a Greek tragedy.

In the stands, hundreds of people sat waiting their turn. Like Adam, most had been there since the wee hours. The longest line of all was for endodontic services, such as root canals, which can cost thousands and are not covered by Maryland’s Medicaid program.

James Hart drove up from Waldorf, 35 miles away, for a root canal that he has needed for three months. A clinic referred him here after quoting him $1,300.

Olga Khazan/Atlantic

Rochelle Hernandez, from Laurel, also needed a root canal. She had tried to sign up for dental insurance, but after paying a few other bills, she couldn't afford the premium. Two weeks ago, she was able to get a dentist to take X-rays of the offending molar by using a discount coupon. But when that office told her it would be $2,000 to fix the problem, she knew she’d be headed to the UMD clinic instead.

Several other people waved me away when I approached them, saying they didn’t feel like talking. I probably wouldn’t have, either, if my teeth were hurting and my only hope of stopping the pain was a day-long wait and a very public drilling.

About a third of people in the U.S. don’t visit the dentist every year, and more than 800,000 annual ER visits arise from preventable dental problems. A fifth of Maryland residents have not visited a dentist in the past five years. Despite the fact that dental procedures are some of the most expensive office visits, dental coverage is treated like a garnish—the parsley of the insurance world.

“Medicaid doesn't acknowledge that you have teeth unless you're a child,” said Thomas Ritter, a dentist who was volunteering at the event.

One reason for this is that since the beginning of time, dentistry and medicine have been considered inherently distinct practices. The two have never been treated the same way by either the medical system or public insurance programs. But as we learn more about how diseases that start in our mouths can ravage the rest of our bodies, it’s a separation that’s increasingly hard to rationalize.