He said that tooth decay is rising sharply in Africa because developing countries are becoming more like Western nations in some ways.

“It is likely to be related to a change in diet. Our industrialized diet leads to chronic disease, which includes carries. And that may be the main explanation.”

The diets of developed nations are rich in sugar, a leading culprit in oral health problems. Marcenes says prior to the 19th Century, people had few cavities because sugar was not readily available. It’s also a major contributor to obesity.

Developed nations dramatically reduced the incidence of tooth decay and cavities by adding fluoride to their drinking water.

He said, “The fluoridation of the water is a highly important issue, and yes, it came from research in America. It has contributed enormously to that reduction in carries.”

But while the fluoride made teeth more resistant to the bacteria that cause tooth decay, it also allowed people to eat more sweets.

Oral health problems, Marcenes said, have a major negative effect on a person’s quality of life. For one, they make eating difficult. Second, people may change what they eat and opt for softer foods, such as those with more fat. However, the biggest issue, he found, is both social and psychological.

“We have very strong evidence in the literature that the mouth plays a big role on socialization. People feel embarrassed about having bad teeth. Then they tend to smile less. They tend to communicate less. And the familiar thing is to see someone laughing with their hand in front of the mouth because they don’t want people to see.”