SEATTLE — In the surgical wing of the Center for Pediatric Dentistry at Seattle Children’s Hospital, Devon Koester, 2 1/2 years old, was resting last month in his mother’s arms as an anesthesiologist held a bubble-gum-scented mask over his face to put him under. The doctors then took X-rays, which showed that 11 of his 20 baby teeth had cavities. Then his pediatric dentist extracted two incisors, performed a root canal on a molar, and gave the rest fillings and crowns.

Devon’s mother, Melody Koester, a homemaker from Stanwood, Wash., and her husband Matthew, an information technology manager, said they began worrying about brushing Devon’s teeth only after Melody Koester noticed they were discolored when he was 18 months old.

“I had a lot on my mind, and brushing his teeth was an extra thing I didn’t think about at night,” she said.

The number of preschoolers requiring extensive dental work suggests that many other parents make the same mistake.

The Centers for Disease Control and Prevention noted an increase, the first in 40 years, in the number of preschoolers with cavities in a study five years ago. But dentists nationwide say they are seeing more preschoolers at all income levels with six to 10 cavities or more. The level of decay, they added, is so severe that they often recommend using general anesthesia because young children are unlikely to sit through such extensive procedures while they are awake.

There is no central clearinghouse for data on the number of young children undergoing general anesthesia to treat multiple cavities, but interviews with 20 dentists and others in the field of dental surgery suggest that the problem is widespread.

“We have had a huge increase in kids going to the operating room,” said Dr. Jonathan Shenkin, a pediatric dentist in Augusta, Maine, and a spokesman for the American Dental Association. “We’re treating more kids more aggressively earlier.”

But such operations are largely preventable, he said. “I have parents tell me all the time, ‘No one told us when to go to the dentist, when we should start using fluoride toothpaste’ — all this basic information to combat the No. 1 chronic disease in children.”

Dentists offer a number of reasons so many preschoolers suffer from such extensive dental decay. Though they are not necessarily new, they have combined to create a growing problem: endless snacking and juice or other sweet drinks at bedtime, parents who choose bottled water rather than fluoridated tap water for their children, and a lack of awareness that infants should, according to pediatric experts, visit a dentist by age 1 to be assessed for future cavity risk, even though they may have only a few teeth.

And because some toddlers dislike tooth-brushing, some parents do not enforce it.

“Let’s say a child is 1 1/2, and the child screams when they get their teeth cleaned,” said Dr. Jed Best, a pediatric dentist in New York. “Some parents say, ‘I don’t want my little darling to be traumatized.’ The metaphor I give them is, ‘I’d much rather have a kid cry with a soft toothbrush than when I have to drill a cavity.’”

Major procedures

Dental decay often starts with a dull ache that toddlers cannot distinguish from teething. That is why parents do not realize their child’s teeth are infected until they break or the pain becomes so acute that the child cannot sleep, said Dr. Joel Berg, director of the Center for Pediatric Dentistry, a joint venture since 2010 between the University of Washington and Seattle Children’s Hospital, which built a surgical wing because of demand for oral surgery for preschoolers.

With a cooperative child, a cavity — or even many — can be treated in a dentist’s office with an injection of local anesthesia and an episode of “The Backyardigans” to distract patients.

But dentists routinely recommend general anesthesia for preschoolers with extensive problems, particularly if they will not even let X-rays be taken. The cost to parents for dental restoration under general anesthesia for a child ranges from $2,000 to $5,000 or more, depending on insurance coverage and the amount of work, several dentists said.

Dr. Megann Smiley, a dentist-anesthesiologist at Nationwide Children’s Hospital in Columbus, Ohio, is used to hearing parents question the need for general anesthesia to fix their children’s infected teeth.

“It seems like putting a match out with a fire hydrant,” Smiley said. “But if any of us tried to get 12 teeth treated, we wouldn’t think that’s small.”

The dental surgery center at Nationwide has three operating rooms, which staff members and local dentists used to treat roughly 2,525 children in 2011, 6 percent more than in 2010. The average age of patients is 4, and most have decay in six to eight teeth, she said.

“The most severe cases have 12 or 16, which is seen several times a week,” Smiley added.

Of course, the lack of money or insurance can be an issue, but several dentists in interviews nationwide attributed extensive cavities in part to lax parenting, at all income levels.

“It’s not just about kids in poverty, though kids of lower socioeconomic status tend to get more cavities,” said Dr. Rochelle Lindemeyer, director of the pediatric dentistry residency program at Children’s Hospital of Philadelphia and the University of Pennsylvania dental school.

Affluent families may have nannies who “pacify kids by giving them a sippy cup all day,” Lindemeyer said.

Brushing teeth twice a day used to be nonnegotiable, she said, but not anymore.

“Some parents say: ‘He doesn’t want his teeth brushed. We’ll wait until he’s more emotionally mature.’ It’s baffling.”