One in 10 children develop less than the normal 28 adult teeth, a condition that could adversely affect their bite and cause other dental problems, according to a nationwide survey released Saturday by the Japanese Society of Pediatric Dentistry.
The finding poses a problem because only a limited number of dentists can treat the condition, and it's expensive, said Yoichi Yamasaki, a professor of pediatric dentistry at Kagoshima University who was in charge of the study.
The survey covered 15,544 children at least 7 years old who visited dentists for reasons other than congenital missing teeth from 2007 to 2008 in Tokyo and 11 other prefectures. It found the condition in 1,568 — 9.1 percent of boys and 11.0 percent of girls.
Of the total, 2.5 percent had fewer than normal teeth in the upper jaw, 5.7 percent in the lower jaw and 1.9 percent in both. The most common condition involved a lack of lower second molars that should be located fifth from the center.
The cause of the condition is largely unknown except for some genetic cases. Possible treatments include teeth-straightening and implants, but only a small percentage of Japan's roughly 60,000 dental clinics can handle them, Yamasaki said.