In Japan, there is currently a great disparity in children's dental health. According to government figures, almost 60% of 5-year-olds have no cavities, but others have more than 10 seriously decaying teeth. Officials are now using a variety of approaches to try and tackle around the problem.
Children at one dental clinic in Fukuoka city, western Japan are not there because of cavities.
They are there for the latest preventive care, including a sealant used to fill in recesses and a fluoride treatment.
"I've been bringing my child since they were one and a half," says one mother.
Japan has seen a dramatic drop in the number of children with cavities over the last 40 years, thanks to campaigns to raise awareness of dental hygiene.
But an NHK survey in Fukuoka Prefecture across 117 elementary and junior high schools revealed some alarming signs. Around one third of the schools had children with many cavities.
Some were found to have teeth so decayed that without treatment they would lose them all.
One factor is that some single parents and those in financial difficulty can't afford proper care.
One three-year-old girl has cavities in almost every tooth.
The mother of the child divorced last year and she's been raising her daughter alone, while working as a store clerk. The situation has left her short of time.
"I couldn't ask my boss for time off for a dental visit because I only just started working," she says. "I realize that my daughter's condition is my fault."
Local dentists refer a number of children to this university-affiliated hospital in Fukuoka city.
Some are in such a serious condition that they need a general anesthetic for treatment. The waiting list is months long.
A professor at Hiroshima University, Katsuyuki Kozai, has spent years studying how a child's home environment affects their dental health. He has been warning parents that they can't neglect their children's teeth.
Dental neglect refers to a situation where parents fail to provide their children with adequate brushing and flossing or dental treatment. The professor says that in some cases this happens because the parents are too busy with work or because they have limited finances.
"The number of children living in poor or fatherless families is said to be growing," says Kozai. "If many parents can't afford to maintain their kids' oral health, I'm afraid that we'll see more and more children with these problems."
Kozai is also worried about other long-term impacts. One patient's adult tooth already had a cavity because of the severely decayed tooth it replaced.
Primary teeth can easily decay secondary teeth. This can affect the person's health throughout their life.
Some schools are taking steps to protect children's teeth. An elementary school in Niigata Prefecture has been working with a university to raise awareness among parents.
A book on dental health plays a key role. Each student is given a copy.
If serious cavities are found, the school pastes photos of the teeth on the children's notebooks, so that their parents can see the need for care. This effort has been effective in encouraging parents to rethink putting off their children's visits to the dentist.
But this still was not enough. So, the school is trying other approaches.
They have the children rinse their teeth with fluoride once a week.
Severe tooth decay at the school has dropped to an average of less than one cavity per child.
"We don't mean to blame parents for their children's dental problems," says Mika Kogure, a professor at Meirin College. "We're trying to find easier ways for them to take care of them. As adults, we have to work together to look after children's teeth."
Dental health awareness in Japan has dramatically increased over the past 40 years, but some children have not benefited. Hopefully these public health efforts will result in better dental care for more kids.