Rotting teeth, swollen gums and oral cancers: nearly half the world's population suffer from mouth diseases, the World Health Organization said Thursday.

A new report highlighted glaring inequities in access to oral health services, saying it badly affected the most vulnerable and disadvantaged populations.

"Oral health has long been neglected in global health," WHO chief Tedros Adhanom Ghebreyesus said, insisting that "many oral diseases can be prevented and treated with the cost-effective measures."

The UN health agency found that 45 percent of the global population, or around 3.5 billion people, are battling tooth decay, gum disease and other oral illnesses.

The report, the first comprehensive picture of the situation across 194 countries, found that global cases have increased by one billion over the past 30 years.

The WHO said that was "a clear indication that many people do not have access to prevention and treatment of oral diseases."

The most common diseases are dental caries, or tooth decay, severe gum disease, tooth loss and oral cancers.

Untreated dental caries is the single most common condition, affecting some 2.5 billion people around the world.

Severe gum disease, which is a major cause of total tooth loss, is estimated to affect around one billion people.

And approximately 380,000 new cases of oral cancers are diagnosed every year, WHO said.

Glaring inequities

Three-quarters of those suffering from oral diseases live in low and middle-income countries, the report found.

And in all countries, people on low incomes, the disabled, older people living alone or in care homes, those living in remote and rural communities, or minority groups carry a higher burden of oral diseases, it said.

These patterns are the same found for other non-communicable diseases such as cancers, cardiovascular diseases and diabetes, WHO said.

The risk factors are also similar, with high sugar intake, tobacco use and alcohol abuse taking their toll.

Thursday's report highlighted barriers to delivering adequate oral health services, including dentist visits, which often require high out-of pocket expenses.

This can lead to "catastrophic costs and significant financial burden for families and communities," WHO said.

At the same time, reliance on highly specialised providers and high-tech equipment make these services inaccessible to many.

Inadequate information and surveillance also mean that many people go far too long before seeking or receiving treatment.

WHO presented a long list of proposals to address the problem, including calling for countries to include oral health services in their primary health care systems.