Dental health is a common concern, and tooth decay remains one of the most widespread chronic conditions affecting adults globally. As people live longer and retain their natural teeth for more years, the cumulative effects of dental disease become more pronounced. Understanding the national average for cavities and the factors that influence this number provides a necessary perspective on the state of oral health.
The National Average: Defining Adult Cavity Prevalence
The statistical answer to how many cavities most adults have is complex, as it includes both past and present decay, not just active holes. Data from the National Health and Nutrition Examination Survey (NHANES) reveals that nearly 90% of adults between the ages of 20 and 64 have experienced decay in their permanent teeth at some point. This high percentage reflects a lifetime of exposure to bacteria and dietary sugars that erode tooth enamel.
When looking at the average number of affected teeth, the Decayed, Missing, or Filled Teeth (DMFT) index is used. For working-age adults (20 to 64 years old), the mean DMFT score is approximately 9.3 affected teeth. This composite score indicates that, on average, over nine teeth have either been decayed, missing due to decay, or filled with a restoration.
Analyzing the components of this average provides a clearer picture of dental health. For adults who have experienced decay, the most recent data shows an average breakdown of 0.7 actively decayed teeth, 6.0 filled teeth, and 2.0 teeth missing because of decay. While the filled component is the largest, indicating past treatment, about one in five adults aged 20 to 64 still has at least one untreated cavity. This figure highlights persistent access and care gaps.
Factors Driving Variation in Cavity Counts
Individual DMFT scores vary significantly across the population, driven by a combination of factors. Age is one of the strongest determinants, as the DMFT score naturally increases over time due to the accumulation of decay, restorations, and tooth loss. Older adults, for instance, have higher rates of both decayed and missing teeth compared to younger age groups.
Socioeconomic status (SES) also plays a substantial role, with lower income and education levels being consistently linked to higher rates of untreated decay. Adults with family incomes below the federal poverty level are disproportionately at risk for having active cavities. This disparity is often attributed to reduced access to regular preventive dental care and a lack of insurance coverage.
Lifestyle choices are also major contributors to the risk profile for decay. For example, current smokers have a notably higher mean number of decayed and missing teeth compared to non-smokers. Similarly, dietary habits, such as frequent consumption of sugary foods and drinks, directly influence the oral environment and accelerate enamel demineralization.
How Dentists Measure and Track Tooth Decay
Dental researchers and practitioners rely on the Decayed, Missing, or Filled Teeth (DMFT) index to provide a standardized measure of caries experience. This index quantifies the lifetime history of tooth decay by summing three distinct categories of permanent teeth. The first component, “D” (Decayed), represents teeth with active, untreated cavities.
The “M” (Missing) component counts teeth extracted due to decay or abscess, excluding those removed for orthodontic reasons. The “F” (Filled) component includes teeth restored with fillings, crowns, or other dental work to repair damage caused by caries. A healthy mouth with no decay history has a DMFT score of zero, while a score of 32 indicates every tooth has been affected.
The DMFT index allows for consistent monitoring of oral health trends across different populations and decades. Researchers use the index to track the effectiveness of public health interventions, such as fluoridation programs, and identify specific groups needing targeted dental services. The index provides a single number that summarizes the cumulative impact of dental disease.