The signs of a cavity are small white chalky spots on the enamel, brown or black discoloration, visible holes or pits, sensitivity to hot, cold, or sweet, pain when you bite down, and persistent bad breath. Which of those signs shows up depends entirely on how deep the decay has traveled. Around 90.9% of American adults between 20 and 64 have had a cavity in their permanent teeth, according to the Centers for Disease Control and Prevention, so this is the most common chronic disease in the country. Below we cover what a cavity looks like at each stage, what it feels like and why the earliest ones feel like nothing at all, how to separate a real cavity from a harmless stain, and the exact sequence a dentist uses to confirm one.
Key Takeaways
- Early cavities produce no symptoms because enamel contains no nerve endings, so a lesion confined to enamel physically cannot hurt.
- A cavity moves through five stages, and only the first one is fully reversible.
- Cavities are darker than stains and usually appear as one spot on one tooth, while stains tend to affect several teeth at once.
- Dentists confirm a cavity in three steps: visual inspection, tactile probing with an explorer, and X-rays for surfaces the eye cannot reach.
- X-rays are excellent at ruling a cavity in and poor at ruling one out. Specificity for lesions between teeth runs about 97% while sensitivity runs about 24%, according to a meta-analysis published in the Journal of Dentistry.
- Molars account for more than 90% of untreated cavity cases in adults, and molar grooves and contact points are the two spots you cannot see in a mirror.
What Are the Signs of a Cavity?
The signs of a cavity are white chalky spots, brown or black discoloration, visible holes or pits, sensitivity to hot, cold, or sweet foods, pain when biting or chewing, and chronic bad breath or a bad taste. The sign you notice tells you roughly how deep the decay already is, because each layer of the tooth produces a different signal.
Each layer matters because a tooth is three layers deep. Enamel is the hard outer shell. Dentin sits beneath it and is far softer and porous. Pulp is the soft center holding the nerves and blood vessels. Decay produces visible changes while it is still in enamel and produces sensations only after it reaches dentin.
Reaching dentin is what most people mistake for the beginning. Roughly 26.6% of adults aged 20 to 64 currently have untreated tooth decay according to the Centers for Disease Control and Prevention, and a large share of that group has no idea, because the decay has not yet crossed into a layer that can report itself. Regular professional cleaning appointments exist largely to catch the silent stage.
What Does a Cavity Look Like?
A cavity looks like a small white chalky patch in its earliest form, then turns light brown, then dark brown, then black as the decay deepens. Color is the most reliable visual indicator of depth, and it darkens in a predictable order. More than 80% of Americans have at least one cavity by their mid-30s according to Cleveland Clinic, which means most adults have watched this sequence happen without recognizing it.
The sequence has five recognized stages, and the stage determines both what you see and what your options are.
What Does Stage 1 Cavity Look Like?
A stage 1 cavity looks like a small, white, chalky spot on the tooth surface, with no hole and no darkening. This stage is called demineralization, and the white appearance comes from minerals leaving the enamel and changing how light passes through it. Stage 1 is the only stage that is fully reversible, which is why it is worth learning to recognize.
What Does a Stage 2 Cavity Look Like?
A stage 2 cavity looks like a white spot that has turned a light brownish color, and a small hole may now be visible on the surface. Stage 2 is enamel decay, meaning the mineral loss has progressed far enough to break down enamel structure rather than only weaken it. A hole at this stage is often small enough that food starts catching in it before you can see it clearly.
| Stage | What it looks like | What it feels like | Reversible |
|---|---|---|---|
| 1. Demineralization | Small white chalky spots | Nothing | Yes |
| 2. Enamel decay | White spots turn light brown, small holes appear | Usually nothing | Only while confined to enamel |
| 3. Dentin decay | Spots turn darker brown | Sensitivity to hot, cold, and sweet | No |
| 4. Pulp damage | Dark brown or black spots, gums may redden and swell | Pain, often throbbing | No |
| 5. Abscess | Facial swelling, sometimes a pimple on the gum | Pain radiating into the jaw or face | No |
Sources: Cleveland Clinic five-stage tooth decay model; Journal of Dentistry, systematic review of professionally applied fluoride and enamel remineralization.
What Does a Cavity Feel Like?
A cavity feels like nothing at all in its early stages, then produces sharp sensitivity to hot, cold, or sweet once decay reaches dentin, then becomes a dull throb or ache once it reaches pulp. Pain is a late signal, not an early one. Working-age adults average nine permanent teeth that are decayed, missing, or filled according to the National Institute of Dental and Craniofacial Research, and very few of those teeth announced themselves early.
Announcing itself is something a cavity is physically unable to do at first, and the reason is anatomical rather than behavioral.
Why Can’t You Feel an Early Cavity?
You cannot feel an early cavity because enamel contains no nerve endings, so damage confined to enamel has nothing to transmit a signal through. Enamel is the hardest substance in the human body and it is essentially mineral, with no living cells and no nerve supply. Damage to it registers as nothing.
Nothing changes until decay crosses into dentin. Dentin is threaded with microscopic channels called dentinal tubules, and those tubules connect directly to the nerve inside the pulp. Once decay opens those channels to the outside, temperature and sugar reach the nerve through them, and the tooth finally reports the problem it has had for months or years.
Can a Cavity Cause Sensitivity to Cold?
Yes, a cavity can cause sensitivity to cold, and cold sensitivity is one of the most common first sensations patients report. The distinguishing detail is location and duration. Cavity sensitivity is usually localized to one tooth and gets worse over weeks, while general cold sensitivity across several teeth more often points to exposed root surfaces or worn enamel rather than decay.
How Can You Tell a Cavity From a Stain?
You can tell a cavity from a stain by color depth, by how many teeth are involved, and by texture. A cavity is darker than a stain, usually appears as one spot on one tooth, and feels soft or catches a fingernail, while a stain is lighter, spreads across several teeth, and feels smooth.
Texture is the detail most people never check. Here is what separates the two:
- Number of teeth. Stains from coffee, tea, red wine, or tobacco land on multiple teeth in a similar pattern. One isolated dark spot on one tooth is far more likely to be decay.
- Color depth. Stains tend toward yellow, tan, or grayish brown. Cavities run darker, into deep brown and black.
- Location. Stains gather where the tooth meets the gum and in surface grooves across the whole arch. Cavities concentrate in pit-and-fissure grooves on chewing surfaces and at the contact points between teeth.
- Texture. Stained enamel stays hard and smooth. Decayed enamel softens, and a decayed groove can catch a fingernail or a floss strand.
- Response to cleaning. A stain lightens after a professional cleaning. Decay does not change at all.
- Change over time. Stains stay roughly the same for months. Decay expands and darkens.
What Else Can Look Like a Cavity?
Several conditions besides decay look or feel like a cavity, including gum recession, worn enamel from clenching, cracked enamel, a failing older filling, and normal dark staining inside a deep groove. Each one produces a symptom pattern close enough to fool careful self-inspection.
Self-inspection fails most often on the recession pattern. Gum recession exposes root surfaces that were never designed to be exposed, and root surfaces are softer than enamel and far more temperature-sensitive. A patient with recession often reports exactly the cold sensitivity a dentin cavity produces, on several teeth at once, with no decay present anywhere.
Another common lookalike comes from bite force rather than bacteria. Chronic clenching and grinding wears notches into enamel at the gum line and creates hairline cracks across chewing surfaces, and both can darken with normal staining until they read as decay in a mirror.
How to 100% Know If You Have a Cavity?
To know with certainty whether you have a cavity, you need a dental exam, because the two most common cavity locations are physically impossible to inspect yourself. Certainty requires instruments and imaging, not a mirror and a phone light. Molars account for more than 90% of untreated cavity cases in adults, according to research published in the Journal of the American Dental Association, and molars are the hardest teeth in the mouth to see.
Seeing them is only half the problem. The other half is that a cavity between two teeth is hidden behind the tooth in front of it, no matter how good the light is.
Where Do Cavities Usually Form?
Cavities usually form in three places: the pit-and-fissure grooves on the chewing surfaces of back teeth, the contact points where two teeth touch, and exposed root surfaces at the gum line. All three share one feature, which is that a toothbrush bristle cannot reach the bottom of them.
Reaching the bottom of a fissure is beyond what any brush can do, because the deepest fissures are narrower than a single bristle. Contact points between teeth are sealed against each other and only floss or an interdental brush ever touches them. Root surfaces sit below the gum line where recession has exposed them. Only 65.5% of American adults aged 18 and over had a dental exam or cleaning in the past year, according to the Centers for Disease Control and Prevention, which leaves a third of the country with these three sites uninspected. A regular dental exam covers all three.
How Do Dentists Tell If You Have a Cavity?
Dentists tell if you have a cavity through a three-part sequence: visual inspection under strong light and magnification, tactile probing with an instrument called an explorer, and X-rays of the surfaces that cannot be seen directly. No single one of those three is conclusive on its own, which is why all three are used together.
- Visual inspection. We dry the tooth first, because a demineralized white spot becomes visible when the surface moisture is removed and often disappears again when it is wet. Then we examine each surface under light and magnification for color change, loss of gloss, and surface breakdown.
- Tactile probing. An explorer is drawn across suspicious areas. Healthy enamel feels glassy and hard. Decayed enamel feels soft, and the instrument tip catches or sinks slightly. Probing confirms what the eye suspects.
- Bitewing X-rays. Bitewings image the contact points between teeth and the depth of decay beneath the surface. Decay shows up as a darker shadow because demineralized tooth structure stops fewer X-rays than healthy structure does.
- Depth assessment. We measure how close the shadow comes to the pulp, since that distance decides whether the tooth needs a filling or something more involved.
- Comparison against your history. We compare today’s images against your previous ones. A shadow that has not changed in three years behaves differently from one that appeared since your last visit, and the change over time often matters more than the shadow itself.
Comparing images over time is where equipment quality shows. We built both our San Ramon and Modesto offices around a 3D imaging center and current digital X-ray technology, which is also why we can look at the same tooth across several years without guessing. You can see the full range of what we treat across our treatments.
What Does a Cavity Look Like on an X-Ray?
A cavity looks like a dark shadow or notch on an X-ray, usually shaped like a wedge or a triangle pointing inward from the tooth surface. The shadow appears dark because decay has removed mineral, and less mineral means fewer X-rays are absorbed in that spot. Healthy enamel appears bright white by comparison, and dentin appears slightly grayer than enamel even when it is perfectly healthy.
Healthy anatomy is exactly what makes X-ray reading harder than it sounds. Normal grooves, overlapping tooth edges, and the natural difference in density between enamel and dentin all produce shadows that resemble early decay. Reading past those requires knowing what that particular mouth normally looks like.
How Accurate Are Cavity Detection Methods?
Cavity detection methods are far better at confirming decay than at ruling it out, and the gap between those two abilities is large. X-rays catch only about a quarter of early lesions between teeth, but when an X-ray does show one, it is right about 97% of the time.
Two terms explain that split, and both are worth knowing before reading the table. Sensitivity means how often a method finds decay that is genuinely there. Specificity means how often it correctly clears a spot that is genuinely healthy. A method can score very high on one and poorly on the other, and X-rays do exactly that.
| Method | What it detects best | Sensitivity | Specificity |
|---|---|---|---|
| Visual inspection | Early lesions on surfaces you can see | 80% | 75% |
| X-ray, between teeth | Confirming decay at contact points | 24% | 97% |
| X-ray, chewing surfaces | Decay under grooves and fissures | 35% | 78% |
| Laser fluorescence | Early mineral loss before a hole forms | 80% | 80% |
| Near-infrared transillumination | Lesions between teeth, without radiation | 97% | 91% |
Sources: Journal of Dentistry, systematic review and meta-analysis of radiographic caries detection, pooling 117 studies across 13,375 teeth and 19,108 tooth surfaces; meta-analysis of visual, fluorescence, and photographic examination of initial caries lesions; systematic review of near-infrared light transillumination for interproximal lesions.
The numbers in that table are the reason a dentist uses several methods rather than trusting one. They are also the reason a clear X-ray is not the same thing as a clean bill of health, and why an experienced eye still matters more than any single instrument. Dr. Fernández has spent over 25 years reading these surfaces, and you can read about both doctors’ training on our about us page.
What Is the No. 1 Cause of Cavities?
The number one cause of cavities is acid produced by bacteria feeding on sugars and starches in your mouth. Bacteria convert those carbohydrates into acid, the acid dissolves mineral out of enamel, and repeated acid exposure over time produces a cavity. Sugar itself does not damage teeth directly, which is a distinction worth holding onto, because it changes what actually reduces risk.
Reducing risk depends on exposure frequency more than exposure quantity. Each time carbohydrates reach the bacteria in plaque, acid production runs for a stretch of time before saliva neutralizes it. Six small snacks across a day produce six acid cycles, while the same total sugar eaten at one sitting produces one. Frequency is the variable most people never adjust.
Time compounds the effect, and the CDC data shows it plainly. Caries experience climbs from 82.1% of adults aged 20 to 34, to 93.6% at ages 35 to 49, to 97.4% at ages 50 to 64. Dry mouth accelerates the same process, since saliva is what neutralizes acid and washes away food debris, and many common medications reduce saliva flow. Pain from clenching or from jaw joint pain gets misread as decay often enough that we check for both.
Will a Cavity Go Away on Its Own?
A cavity in the demineralization stage can reverse on its own with fluoride and improved hygiene, but a cavity that has broken through into dentin cannot. Enamel can rebuild lost mineral. Dentin cannot, and neither can a hole. The dividing line between those two outcomes is the single most useful fact in this article.
Rebuilding lost mineral is called remineralization, and the evidence behind it is strong. A systematic review published in the Journal of Dentistry found that 5% sodium fluoride varnish remineralized 63.6% of early enamel caries in pooled analysis. A randomized trial reported in the Journal of the American Dental Association found that 81.2% of active enamel lesions became inactive in the fluoride varnish group at nine months, against 37.8% in the control group.
Those two numbers only apply to lesions still confined to enamel. Once decay crosses into dentin, the tooth has lost structure rather than only mineral, and lost structure has to be replaced rather than rebuilt. Patients we monitor across Modesto often have a white spot we watch and re-image for a year rather than drilling it, and routine visits are what make that kind of watching possible.
Can I Wait 2 Years to Fill a Cavity?
Waiting two years to fill a cavity gives the decay two years to deepen, and decay that starts in enamel will usually reach dentin and often reach pulp in that window. What changes during the wait is not whether the tooth needs treatment but how much treatment it needs. A cavity caught in enamel needs a small filling. The same cavity two years later can need a crown or root canal treatment.
The scale of what a wait takes away shows in national data. Research published in the Journal of the American Dental Association found untreated caries severity averaging 3.50 affected teeth per case among adults aged 20 to 34, dropping to 2.62 teeth among adults aged 50 to 64, which reflects teeth being lost rather than decay slowing down.
Losing teeth is the far end of the timeline, and it is entirely avoidable at the front end. Timely dental fillings preserve the maximum amount of natural tooth structure, which is the whole point of catching decay early.
How Can You Tell How Bad a Cavity Is?
You can tell how bad a cavity is by what it looks like and what it feels like, using the same staging that guides treatment. A white or light brown spot with no sensitivity is shallow. Darker brown with hot and cold sensitivity means the decay has reached dentin. Throbbing pain, a dark tooth, or swelling means it has reached pulp. Only an X-ray shows the actual remaining distance to the nerve.
What Happens If You Don’t Fill a Cavity?
If you do not fill a cavity, the decay spreads through dentin into the pulp, infects the nerve, and eventually forms an abscess at the root tip. Decay does not stall and it does not heal once it passes enamel. It advances. Around 96.2% of American adults aged 65 and over have caries experience according to the Centers for Disease Control and Prevention, and the teeth lost along the way were nearly all small cavities once.
Small cavities become large ones faster than most people expect, because dentin is much softer than enamel. Once decay breaches the enamel shell it spreads sideways and downward through dentin at a noticeably quicker rate, which is why a cavity that looked like a pinpoint on the surface can undermine half the tooth beneath it.
Undermined tooth structure changes what treatment is possible. A tooth with a small dentin cavity takes a filling. A tooth with widespread dentin loss and an infected pulp needs root canal treatment and usually a crown, and a tooth that has lost too much structure to support either becomes a candidate for oral rehabilitation instead. Roughly a quarter of adults in every working-age bracket are carrying untreated decay right now, at 25.9% for ages 20 to 44 and 25.3% for ages 45 to 64.
Can a Tooth Rot Under a Crown?
Yes, a tooth can decay under a crown, and this is one of the hardest cavities to catch. Decay under a crown starts at the margin where the crown meets natural tooth, because that seam is the only route bacteria have into the tooth beneath. The crown itself cannot decay, since porcelain and metal are not biological material, but the natural tooth underneath it still can.
The tooth underneath is also invisible. A crown blocks light and blocks the explorer, so visual inspection and probing both stop at the crown edge, and even X-rays struggle because metal and dense ceramic block X-rays completely and cast a bright shadow over the tooth structure behind them.
Blocked views mean the signs matter more here than anywhere else. A dark line appearing at the gum line edge of a crown, new sensitivity in a crowned tooth, a crown that suddenly feels rough at the margin, or floss that catches or shreds at one specific spot all warrant a look. A well-fitted dental crown with a sealed margin resists this for years.
Margin quality is where laboratory craft actually shows, and it is the difference between a crown that seals for a decade and one that leaks in two years. You can see how we approach that in our case results.
Frequently Asked Questions
Can You Smell a Cavity?
You can sometimes smell a cavity, because decay produces a persistent bad odor and a bad taste that brushing does not clear. The smell comes from bacteria breaking down trapped food inside the decayed space and releasing sulfur compounds as waste. A cavity creates a crevice too narrow for a brush bristle to reach, so the debris stays and the odor keeps returning. Persistent bad breath despite good hygiene is worth having examined.
What Does a Cavity Look Like Between Teeth?
A cavity between teeth usually looks like nothing from the front, because the contact point where two teeth touch is hidden behind the tooth in front of it. Signs that show up instead are floss catching or shredding at one specific spot, food packing in the same place after every meal, a faint dark shadow visible through the enamel from the biting surface, and new sensitivity in that area. Confirming a cavity between teeth requires a bitewing X-ray or near-infrared imaging.
How Do You Check for a Cavity at Home?
You check for a cavity at home by drying your teeth with a tissue and examining each surface under bright light for white chalky patches, dark spots, or holes, then running floss between every pair of teeth to find any spot where it catches or shreds. Home checking finds surface cavities on front teeth reasonably well and misses cavities between back teeth almost entirely. Visual inspection carries roughly 80% sensitivity even in trained hands under laboratory conditions.
Do All Cavities Need a Filling?
Not all cavities need a filling. A lesion still confined to enamel, showing as a white spot with no break in the surface, can often be arrested and remineralized with fluoride treatment and improved hygiene instead of being drilled. Pooled analysis published in the Journal of Dentistry found 63.6% remineralization of early enamel caries with 5% sodium fluoride varnish. Once the surface has broken and decay has reached dentin, a filling becomes necessary, because lost structure cannot regrow.
What It All Comes Down To
A cavity gives you visual signs long before it gives you painful ones, and the earliest visible sign is the only stage you can still reverse. White chalky spots come first, then light brown, then dark brown and black as decay moves deeper. Sensitivity arrives only after decay crosses out of enamel and into dentin, which means pain marks the point where a filling became necessary rather than the point where the cavity began.
Confirming one takes three methods used together, because each has a blind spot the others cover. That is also why a spot you cannot identify in the mirror deserves a look rather than a wait, since the two most common cavity locations are the two you cannot see. Our San Ramon and Modesto offices both carry the imaging that makes an honest answer possible on the first visit.
If you have found a spot on a tooth, or something has started feeling sensitive that never did before, we would rather look at it while the answer is still simple. Everyone at DDS With A Smile is happy to take a look and tell you plainly what we see.
You are welcome to schedule a visit whenever it suits you.