Other evidence comes from a randomized study in Brazil. In that study, investigators showed one of two images to people responsible for hiring: pictures either of a person without dental problems or with uncorrected dental problems. Those with dental problems were more likely to be judged as less intelligent and were less likely to be considered suitable for hiring.

The relationship between oral health and work has gained new salience in light of Kentucky’s recently approved Medicaid waiver, which permits the state to impose work requirements on some able-bodied Medicaid enrollees. It’s a step that some other states are also considering.

Medicaid takes different forms in different states, and even within states, different populations are entitled to different benefits. Though all states must cover dental benefits for children in low-income families, they aren’t required to do so for adults.

As of January 2018, only 17 state Medicaid programs offered comprehensive adult dental benefits, and only 14 of those did so for the population eligible for Medicaid under the Affordable Care Act. More typically, states offer only limited dental benefits or none.

Dental coverage under most private health care plans isn’t comprehensive, either — people who want it have to buy separate dental plans. But compared with those enrolled in private coverage through an employer or on their own, the population eligible for Medicaid is much more likely to need dental care and much less likely to be able to afford it or coverage for it. People with incomes low enough to qualify for Medicaid are twice as likely to have untreated tooth decay, relative to their higher-income counterparts.

Kentucky offers limited dental benefits to Medicaid enrollees, including those on whom work requirements would be imposed. Those benefits exclude coverage for dentures, root canals and crowns, which could challenge some enrollees’ ability to maintain good oral health and lead to greater emergency department use.

One study found that after Kentucky’s Medicaid expansion in 2014, the rate of use of the emergency department for oral health conditions tripled. Another study found that about $1 billion in annual emergency department spending was attributed to dental conditions, and 30 percent of emergency department visits for dental problems were made by people enrolled in Medicaid.