Tooth decay is the single most common chronic disease in the world. As of 2021, an estimated 2.24 billion people globally have untreated cavities in their permanent teeth, and another 530 million children have decay in their baby teeth. That makes it far more prevalent than diabetes, heart disease, or asthma. If you’re wondering whether your cavity makes you unusual, the short answer is: not at all.
How Many People Have Cavities
Roughly one in four people on the planet is currently living with at least one untreated cavity. In the United States, about 21% of adults aged 20 to 64 have one or more untreated cavities right now. Among young children aged 2 to 5, about 11% already have decay in their baby teeth. By the time kids reach 6 to 11, nearly 3% have untreated decay in their permanent teeth, a number that climbs steadily with age.
These numbers only capture untreated decay. The total number of people who have ever had a cavity is much higher, since filled or crowned teeth don’t show up in “untreated” statistics. When you include past and present cavities, the majority of adults have experienced tooth decay at some point in their lives.
Children Are Hit Early
More than 530 million children worldwide have cavities in their baby teeth, according to the Global Burden of Disease Study. Early childhood caries affects children under six and can begin as soon as teeth emerge. In the U.S., more than 1 in 10 children aged 2 to 5 already have at least one untreated cavity.
Income plays a major role. Children aged 2 to 5 from low-income households are nearly three times as likely to have untreated cavities (18%) compared with children from higher-income families (7%). By ages 6 to 9, about 60% of children from lower-income households have had cavities in either their baby or permanent teeth, compared with 40% from higher-income homes. That gap persists into adolescence: 14% of teens from low-income families have untreated cavities versus 8% from wealthier ones.
Older Adults Face a Different Problem
As gums recede with age, the roots of teeth become exposed, creating a surface that’s softer and more vulnerable to decay than enamel. Root cavities are a distinct challenge for people over 65. Among community-dwelling older adults, studies show root caries prevalence ranges from about 53% to 62%, making it more the norm than the exception.
Tooth loss tells the rest of the story. About 13% of adults 65 and older have lost all their teeth. Among those 75 to 84, only half still have what’s considered a functional set of teeth (21 or more). By age 85 and beyond, that drops to just 32%. Low income more than doubles the risk of complete tooth loss: 30% among lower-income older adults compared with 12% among those with higher incomes.
The Global Picture Is Getting Worse, Not Better
The overall rate of cavities per person has stayed roughly flat since 1990, but because the world’s population has grown, the total number of people affected has surged. In 1990, about 1.46 billion people had untreated permanent tooth decay. By 2021, that number had climbed to 2.24 billion.
The trends split sharply by wealth. In Europe, the total number of people with untreated cavities actually dropped by about 9 million between 1990 and 2021, thanks to fluoridated water, better access to dental care, and public health campaigns. In Africa, the number more than doubled, jumping from 190 million to 400 million over the same period. The pattern is consistent across developing regions: as diets shift toward more processed foods and sugary drinks, decay rises faster than dental infrastructure can keep up. Without effective prevention, cases will continue to grow in lower-income regions for decades.
Why Sugar Intake Matters So Much
Free sugars, the kind added to foods and drinks or naturally present in honey, syrups, and fruit juices, are the single most important dietary risk factor for cavities. Bacteria in the mouth feed on these sugars and produce acid that dissolves tooth enamel. The more sugar you consume and the more frequently you consume it, the more acid your teeth are exposed to throughout the day.
The World Health Organization recommends keeping free sugars below 10% of your total daily calories, which works out to roughly 50 grams (about 12 teaspoons) on a 2,000-calorie diet. Cohort studies consistently show lower cavity rates at this threshold. In one study, Brazilian children whose sugar intake exceeded 16% of calories were nearly three times as likely to develop significant decay compared with those who stayed at or below 10%. Finnish children who kept sugar under 10% of calories had roughly one-third as many decayed, missing, or filled teeth as those who exceeded that level.
Staying under 10% reduces decay but doesn’t eliminate it. The WHO conditionally recommends going further, to below 5% of calories, for the best protection throughout life. That’s about 25 grams, or 6 teaspoons, per day. For context, a single can of regular soda contains about 39 grams of sugar, already exceeding that stricter target.
The Economic Toll
Dental diseases collectively cost the world an estimated $710 billion in 2019. About $387 billion of that went to direct treatment costs: fillings, crowns, extractions, dentures, and emergency visits. The remaining $323 billion came from indirect costs like lost work productivity and reduced quality of life. Those figures have been climbing steadily, up from an estimated $298 billion in direct costs in 2010 and $357 billion in 2015.
For individuals, the financial burden falls hardest on those least able to afford it. The same low-income populations with the highest rates of decay are the ones most likely to delay or skip treatment entirely, which leads to more advanced disease, more pain, and eventually tooth loss. What starts as a preventable cavity can become an extraction, and what could have been managed with routine care becomes a cycle of emergency visits and worsening oral health.