Many Americans find it difficult to obtain adequate dental care, but the problem is particularly acute among older Americans like Mr. Maddalena. Fewer than half of Medicare beneficiaries have visited a dentist in the past year, a rate that sinks to 26 to 28 percent at lower income levels.

At the West Center, where the average patient lives on $850 a month, “they often haven’t seen a dentist in 10 or 20 years,” Dr. Becerra said. “They’d end up in the E.R. when the pain got unbearable.” She has seen patients who have pulled their own teeth.

About 20 percent of Americans over age 65 have untreated cavities, the National Center for Health Statistics has reported, with cavities much more prevalent among blacks, Hispanics and Asians. Among those over age 75, a quarter have lost all their teeth.

Still, better hygiene and fluoridation means more older people have more teeth to preserve, over lengthened life spans, than in the past. Decades back, “losing your teeth and getting dentures was the expectation,” said Dr. Stephen Shuman, who leads the Gerontological Society of America’s oral health group.

Yet dental health gets more challenging at older ages. Gums recede, exposing roots to decay, and bone loss makes teeth less stable. Older people produce less saliva — particularly because they often take drugs that produce dry mouth — which also leaves teeth vulnerable to decay.