SEATTLE — In the surgical wing of the Center for Pediatric Dentistry at Seattle Children’s Hospital, Devon Koester, 2 ½ 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 Mrs. 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 6 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.