A new report says nearly four-billion people – more than half the world’s population – have major tooth decay, or cavities. Health officials warn that poor oral health can lead to social and psychological problems.

Professor Wagner Marcenes led of team of researchers as part of the Global Burden of Disease 2010 study. It listed untreated tooth decay, or cavities, as the most common of all 291 major diseases and injuries.

“It was a massive effort. We had about 500 scientists work on it. And we reviewed all literature, all data on all disease and then came with estimations -- that was the report that has been recently published,” he said.

Marcenes is with the Institute of Dentistry at Queen Mary, University of London.

Tooth decay, or cavities in permanent teeth, is also known as carries.

“Carries is a chronic disease that shares the same risk factors as cancer, cardiovascular disease. What we’re having now is an increase in disease from highly developed countries happening in sub-Saharan Africa and probably it will be in other areas of Africa, too,” he said.

In fact, the study says the “largest increases in the burden of oral conditions” were in sub-Saharan Africa and Oceania. Marcenes was not surprised at the study’s results.

“It tends to get less attention than some other disease. For example, HIV obviously [is] a much more relevant issue for the health of the population,” he said.

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.”

Professor Marcenes said that adolescents with bad teeth can face long-term self-esteem issues.

He hopes African and Asian nations will see the health problems of the West and not follow their dietary example. He’s calling for an “urgent, organized, social response” to the widespread lack of oral health.

“We need a public health approach that deals with the causes of the disease, rather than deal with each disease independently because the most disabling disease share the same cause,” he said.

Marcenes is calling for a holistic approach that includes a healthier diet and the development of new and cheaper dental materials and treatments.