How likely are you to get a cavity?
Everyone knows the rules about brushing and sugar. Almost nobody knows how much difference any of it makes once you put a number on it, or how much of the outcome was decided by saliva chemistry you had no say in. Answer six questions and see where your habits put you against the rest of the adult population. This assessment on Find The Norm uses CDC/NIDCR NHANES 2017-2020 data (N=11,566 adults) and Selwitz et al. 2007 Lancet review to score your cavity risk relative to US adult norms.
Querying population data…
How many lifetime cavities is normal?
Where a lifetime tally sits in the US adult data.
How common are cavities in the US?
The National Health and Nutrition Examination Survey found, across 2017-2020, that 92% of US adults aged 20 to 64 have had dental caries in their permanent teeth, with a mean DMFT score (Decayed, Missing, and Filled Teeth) of 9.3 for that age range. Of that, 0.7 is decayed and still untreated, 2.6 missing and 6.0 filled. Around 25% of adults are walking about with at least one cavity that nobody has dealt with yet.
Prevalence climbs steadily with age, from 85.6% among 20 to 34 year olds to 92% at 35 to 49 and 96.2% at 50 to 64. Some of that is just more years of exposure. Part of it is arithmetic, because DMFT counts everything that has ever happened to a tooth and never goes back down, so a filling done at 19 is still in your score at 60. Older adults also grew up before water fluoridation and sealants were widespread, which means the age gradient is measuring three separate things and only one of them is how anyone brushes today.
| Age group | Caries prevalence | Mean DMFT |
|---|---|---|
| 20 to 34 | 85.6% | ~4.5 |
| 35 to 49 | 92% | ~8.5 |
| 50 to 64 | 96.2% | ~13.8 |
| All adults (20 to 64) | 92% | 9.3 |
What factors most increase cavity risk?
Caries starts with acid, made by Streptococcus mutans and Lactobacillus species feeding on fermentable carbohydrate and dissolving enamel over time, so the factors that move risk most are how often sugar arrives in the mouth and how much plaque gets removed before it does. Access to a dentist sits behind both, because someone has to spot the damage early.
Skipping the second daily brush carries a 1.5 to 2x increase in caries risk. Never flossing adds 1.3 to 1.6x for the cavities that form between teeth, where no brush reaches. Two or more sugary drinks a day runs at 2 to 3x, which comes from the length of the acid exposure rather than the volume of sugar. Leaving more than 2 years between dental visits raises the odds of decay quietly progressing by 1.4 to 2x.
Twin studies put 40 to 60% of the variation in susceptibility down to genetics, working through saliva chemistry, how well enamel mineralised in the first place, and how the immune system handles the bacteria. So the person who flosses religiously and still needs fillings is not doing it wrong, and the friend who never flosses and has none is not proof of anything. Our cavity count calculator shows where lifetime totals rank in the population.
Does brushing or diet matter more?
Diet is the primary driver mechanically, because without fermentable carbohydrate the bacteria cannot make enough acid to dissolve enamel at all, which is why populations eating very little sugar showed close to zero caries regardless of how they cleaned their teeth. Brushing takes the plaque off. What it cannot do is undo a steady drip of sugar, which holds oral pH under 5.5, the point at which enamel starts to dissolve, for long stretches of the day whatever your brushing routine looks like.
In practice the two work on each other. The ADA sets the floor at twice-daily brushing with fluoride toothpaste, daily flossing and sugar kept to few occasions. Preventive dentistry has moved its emphasis from how much sugar to how often, since one large sugary meal produces a shorter acid attack than the same sugar sipped from a bottle across an afternoon.
Frequently asked questions
It applies published risk multipliers to your answers and places the total against the adult population. What it cannot do is see your teeth. Genetics, saliva flow rate, bacterial load, enamel depth and the fluoride in your tap water all move real risk, and none of them are in the six questions. Only a dentist looking at X-rays can tell you whether decay is active right now.
Only at the earliest stage. While the decay is still in the outer enamel, the tooth can pull calcium and phosphate back out of saliva and repair itself, and fluoride varnish or casein phosphopeptide products speed that up. Once it reaches the dentine underneath, the damage is structural and needs restoring. That early window almost always shows on an X-ray before you can feel anything, which is the real argument for check-ups.
A Cochrane Review of 56 randomised controlled trials found oscillating-rotating powered brushes cut plaque by 21% more and gingivitis by 11% more than manual brushing over three months. Caries itself is hard to measure in trials that short. Most of the gain is time, since an electric brush run for the full 2 minutes beats a manual one used for the average 45 seconds. Oral-B and Quip both make oscillating models; if prevention fails, the dental implant cost calculator covers what replacing a tooth costs.
No toothbrush reaches between teeth, whatever the technique, and those surfaces account for a large share of adult caries. Floss breaks up the biofilm sitting in the contact points, and a Waterpik does the same job for anyone who cannot manage string. The ADA is candid that trial evidence linking flossing directly to fewer cavities is thinner than the mechanism suggests, largely because long caries trials cost a fortune to run. Its opposite, whether anyone can brush too much, sits in the brushing frequency calculator.
The 25% figure is mostly about who can get to a dentist. Untreated decay runs far higher among lower-income and uninsured adults, and people without dental insurance are roughly 2.5 times more likely to have it than people with coverage. US dentistry is not built as a public health service the way medicine is in many countries, so a filling someone knows they need can sit undone for years on cost alone.
Both do damage, and drinks add a problem of their own, because people sip them for hours and hold the mouth under the pH where enamel dissolves. A chocolate bar at a meal is one short acid attack, where a 500ml bottle nursed across two hours is a long one. Sugar-sweetened drinks carry a 2 to 3x increase in caries risk on their own, and the citric acid in fizzy ones erodes enamel separately from anything the sugar does.
The six-month rule is convention more than evidence. A Cochrane Review found no good grounds for treating twice a year as better than intervals set by risk, and the ADA now asks dentists to set the gap patient by patient, annually for low-risk mouths and every 3 to 6 months for high-risk ones. What the visit buys you is decay caught while it is still in the enamel, plus the calculus no brush shifts.
Fluoride is the part of the tube that prevents cavities. Non-fluoride pastes still scrub plaque off, and that is all they do. Fluoride hardens enamel into fluorapatite, slows Streptococcus mutans down and rebuilds early lesions, which is about as strong as preventive evidence gets in medicine. The ADA recommends it at every age, children included. Adults want 1,000 to 1,500 ppm, which covers every mainstream brand, and 5,000 ppm is on prescription for high-risk patients.
- CDC/NIDCR. NHANES Oral Health Surveillance Report 2024. Pre-pandemic data 2017 to March 2020. N=11,566 U.S. adults.
- Selwitz RH, Ismail AI, Pitts NB. (2007). Dental caries. Lancet, 369(9555):51 to 59.
- American Dental Association. (2024). Oral Health Topics: Caries Risk Assessment and Management.
- Cochrane Review: Sambunjak D et al. (2011). Flossing for the management of periodontal diseases and dental caries in adults.
- This calculator provides population context only, not a dental diagnosis or a substitute for clinical examination.