The common symptoms of tooth decay are sensitivity to hot, cold, or sweet foods, visible white, brown, or dark spots on a tooth, small holes or pits you can see or feel, food that keeps catching in the same place, and a toothache that will not settle down. Early decay usually causes none of these, which is the part most people do not expect.

Below we walk through the full symptom list in the order symptoms actually appear, explain what is happening inside the tooth at each stage, and give you a clear way to tell whether you need a routine visit, an appointment in the next week, or same-day care. We also cover how fast decay moves, which teeth it hits first, and what can still be reversed.

What Are the Symptoms of Tooth Decay?

The symptoms of tooth decay are sensitivity to hot, cold, and sweet foods, white or chalky spots on the enamel, brown to black staining, visible pits or holes, food catching repeatedly in one spot, continuous toothache, pain when biting down, and bad breath or a foul taste once infection develops. Infection signs also include gum swelling and fever.

Fever and swelling sit at the far end of a sequence that starts silently. Silent is the key word for the earliest stage, because decay that has only touched the outer enamel has not reached any nerve tissue, so there is nothing to feel. Mayo Clinic states plainly that when a cavity is just beginning, you may have no symptoms at all.

No symptoms at all is a common starting point, and the numbers show how common. The CDC’s 2024 Oral Health Surveillance Report found that about 1 in 5 adults aged 20 to 64 has at least one untreated cavity right now, and that untreated decay peaks at roughly 22% among adults aged 20 to 34. Most of those people are not in pain today.

Pain arrives later, and it arrives in a predictable order. Sensitivity comes first, because decay has reached dentin and stimuli can now travel toward the nerve. Visible change comes next, as the enamel surface collapses into a pit. Continuous pain comes last, once the pulp is involved. Reading the symptom you have against that order tells you a great deal about where the decay actually sits.

What Is Tooth Decay, and How Is It Different From a Cavity?

Tooth decay is the process of acid dissolving minerals out of a tooth, and a cavity is the hole that process eventually leaves behind. Decay is the verb and a cavity is the noun. Dentists also call decay dental caries, which is the clinical name for the same disease.

The same disease shows up on a scale rather than as a yes or no. Decay can be active and progressing without any hole existing yet, which is why a dentist can tell you that you have early decay and still not recommend a filling. A cavity, by contrast, means the enamel surface has broken and the damage now needs a restoration to close it.

Closing the gap between those two states is the whole point of early detection, and it works because decay is genuinely reversible in its earliest phase. Cleveland Clinic notes that more than 80% of Americans have at least one cavity by the time they reach their mid-30s, and the National Institute of Dental and Craniofacial Research reports that nearly 90% of adults aged 20 to 64 have had decay at some point, rising to 96% among adults aged 50 to 64. Decay is close to universal. Holes are not, and the difference between those two figures is timing.

What Causes Tooth Decay?

Tooth decay is caused by acid produced when bacteria in dental plaque feed on sugars and starches left on the teeth. Plaque is a sticky, clear film of bacteria that forms on tooth surfaces within hours of brushing.

Bacteria inside that plaque convert carbohydrates from food into acid within minutes of eating. Acid then strips calcium and phosphate out of the enamel surface, a process called demineralization. Demineralization repeats every time you eat, and saliva works to put those minerals back between meals. Decay begins when the stripping outpaces the repair.

Repair falls behind for reasons that go well past brushing habits. These factors raise the risk of decay:

• Frequent snacking or sipping sweetened drinks, which keeps the mouth acidic for most of the day
• Dry mouth, known clinically as xerostomia, which removes saliva’s protective and rinsing effect
• Medications that reduce saliva flow, including many antidepressants and blood pressure drugs
• Gum recession, which exposes root surfaces that have no enamel covering at all
• Older fillings with worn or rough edges that collect plaque a brush cannot clear
• Acid reflux, which washes stomach acid across the enamel
• Deep grooves and pits in the back teeth that trap food particles
• Smoking, with the CDC putting untreated decay prevalence at 27.6% among current smokers
• Low fluoride exposure, though the CDC reports that 72.3% of people served by community water systems, more than 209 million Americans, receive fluoridated water

Fluoridated water helps because fluoride pushes minerals back into weakened enamel. When that balance still tips the wrong way, the damage moves through the tooth in stages, and each stage produces its own set of signs. Our general dentistry exams are built around catching that movement early, well before a patient notices anything.

What Are the Stages of Tooth Decay?

There are five stages of tooth decay: demineralization, enamel decay, dentin decay, pulp damage, and abscess. Each stage reaches deeper into the tooth, and each one changes what you see and what you feel.

What you see and what you feel is the most useful map any patient can carry. The staging framework below follows the clinical model used by Cleveland Clinic, with treatment expectations drawn from standard restorative practice and CDC guidance on early intervention.

Stage	What Is Happening Inside the Tooth	What You Might Notice	Typical Treatment
1. Demineralization	Acid pulls calcium and phosphate out of the enamel surface	Small white or chalky spots, usually no pain	Fluoride and improved home care; reversible
2. Enamel decay	Enamel breaks down and the surface begins to cavitate	Spots turn light brown, a small hole may become visible	Filling
3. Dentin decay	Decay reaches the softer layer under the enamel and moves faster	Sensitivity to hot, cold, and sweet; spots darken	Filling, sometimes a crown
4. Pulp damage	Bacteria reach the nerve and blood vessels, which swell inside a rigid chamber	Continuous pain, pain on biting, dark brown or black spots, gum redness	Root canal therapy, usually with a crown
5. Abscess	Infection forms a pocket of pus at the root tip and spreads into surrounding tissue	Severe pain radiating to the jaw or face, facial swelling, fever, foul taste	Urgent treatment: drainage, root canal, or extraction

What Is Stage 1 of Tooth Decay?

Stage 1 of tooth decay is demineralization, the point where acid has pulled minerals out of the enamel but has not yet broken the surface. Minerals leaving the enamel change how it reflects light, which produces small white or chalky patches, often near the gumline or in the grooves of molars.

Grooves and gumlines hide these patches well, and most people never spot them. This stage carries no pain whatsoever, and it is the only stage that can be fully reversed without drilling.

What Does a Stage 2 Cavity Look Like?

A Stage 2 cavity looks like a light brown spot on the tooth, and often shows a small break or pit where the white chalky patch used to be. The color shift from white to light brown signals that enamel has actually broken down rather than simply weakened.

Enamel that has broken down cannot rebuild itself, so this stage needs a restoration. Most Stage 2 cavities are handled with straightforward dental fillings that remove the decayed portion and seal the opening in a single visit.

What Happens During Stage 4 Tooth Decay?

During Stage 4 tooth decay, bacteria reach the pulp, the innermost layer holding the tooth’s nerves and blood vessels. The pulp swells in response, and because a tooth has no room inside for swelling, that pressure presses directly on the nerve. Nerve pressure is what produces the constant, throbbing pain people associate with a bad tooth.

Pain at this stage does not come and go with hot or cold the way sensitivity does. It lingers, it often worsens at night when you lie down, and biting becomes uncomfortable. Saving a tooth at Stage 4 usually calls for root canal treatment, which removes the infected pulp, disinfects the canals, and seals the tooth so it can stay in place.

How Do I Tell If My Tooth Is Starting to Rot?

You can tell a tooth is starting to rot by checking for white or dark spots in a mirror, running your tongue over the surface for rough or sticky patches, and watching whether floss shreds or catches on the same tooth every time. Floss that shreds in one specific spot is one of the most reliable early clues, and almost nobody looks for it.

Looking for it takes about two minutes. Run through these checks in order:

1. Stand in good light and look at the gumline of every tooth for chalky white patches or dull spots.
2. Check the chewing surfaces of your molars for dark lines or brown pits inside the grooves.
3. Run your tongue across each tooth surface, feeling for rough, sticky, or jagged areas that were smooth before.
4. Floss every contact point and note any spot where the floss frays, shreds, or catches on a rough edge.
5. Pay attention to whether food packs into the same gap after every meal.
6. Test sensitivity deliberately with something cold, and note whether the discomfort fades in seconds or lingers.

Discomfort that lingers is worth flagging, because it points to dentin involvement rather than surface wear. These self-checks catch a good deal, and the early signs of a cavity are worth learning to recognize in detail. What self-checks cannot do is see between teeth or under the enamel surface, which is where a large share of decay actually starts.

How Do You Know If Tooth Decay Is Serious?

Tooth decay is serious when pain lasts more than a few days, wakes you at night, appears when you bite down, or comes with swelling, fever, or a foul taste in your mouth. Swelling and fever mean infection has moved past the tooth into surrounding tissue.

Surrounding tissue reacting is a meaningful line, and so is the character of the pain itself. Sensitivity that flares for a few seconds with cold and then fades usually means dentin exposure. Pain that throbs on its own, without anything touching the tooth, usually means the pulp is inflamed. Pain on biting suggests the infection has reached the ligament holding the tooth in its socket.

The socket and the gum tissue around a decayed tooth often show the problem before anything else does. Redness, tenderness, or gum inflammation concentrated around one tooth rather than spread across the mouth points to that tooth specifically. The CDC reports that nearly half of adults aged 30 and older already show signs of gum disease, so localized swelling around a single tooth is the detail that matters.

Can You Have a Tooth Infection for Years and Not Know It?

Yes, you can have a tooth infection for years and not know it, because once the pulp tissue dies the nerve stops sending pain signals. A dead nerve cannot hurt, so the tooth goes quiet even though bacteria continue to multiply inside it.

Bacteria continuing to multiply eventually produce a chronic abscess at the root tip, and in many cases the body opens a small drainage channel through the gum called a sinus tract. That channel relieves pressure, which keeps pain away, and it often shows up as a small pimple-like bump on the gum that appears, drains, and returns. Some patients notice only an occasional bad taste.

A bad taste with no pain is easy to dismiss, which is why this is one of the strongest arguments for keeping routine x-rays on schedule. An x-ray shows the dark shadow of bone loss at a root tip long before anything becomes uncomfortable.

How Fast Does Tooth Decay Spread?

Tooth decay spreads slowly in most adults, often taking several years to move from the enamel surface into the dentin, but it moves considerably faster in children and in people with high decay risk. Speed depends on saliva flow, diet frequency, fluoride exposure, and where on the tooth the lesion sits.

Where the lesion sits changes the timeline substantially, and longitudinal research has measured it. A radiographic study published in Community Dentistry and Oral Epidemiology tracked adult lesions and estimated that half of the enamel lesions on the sides of teeth had still not reached the dentin roughly 73 months, about six years, after starting. Published Nordic longitudinal data puts the median time for a lesion already sitting at the enamel-dentin border at about three years before it crosses into dentin, with only half of those lesions progressing at all.

Only half progressing is the encouraging part of the picture. A study of caries-active adults published in the Journal of Dental Research found that among early lesions, 51% reversed completely and another 36% simply stopped where they were, leaving 13% that became cavities across a seven-year window.

A seven-year window does not apply to children. A retrospective study in the Journal of Clinical Pediatric Dentistry measured decay in baby teeth moving from outer enamel to the dentin border in roughly 0.8 years, with another 1.4 years to reach inner dentin. Baby teeth have thinner enamel and a proportionally larger pulp, so the same process covers the same ground in a fraction of the time.

How Long Can Tooth Decay Be Left Untreated?

Tooth decay should not be left untreated once it has broken through the enamel, because the tooth cannot repair a cavitated surface on its own and the damage only moves inward from there. Moving inward means each month of delay costs more healthy tooth structure.

Costing tooth structure changes what treatment becomes possible. A small cavity caught in dentin needs a filling. The same cavity left for a year or two may need a crown, and if it reaches the pulp it needs root canal therapy as well. The CDC estimates that about 34 million school hours and 92 million work hours are lost every year in the United States to unplanned and emergency dental care, with roughly $46 billion in productivity lost annually to untreated oral disease. Most of that traces back to problems that started as something small.

Can I Wait 2 Years to Fill a Cavity?

Waiting 2 years to fill a cavity is not advisable, because a confirmed cavity has already passed the point where the tooth can reverse the damage. Two years gives decay enough time in most adults to move from outer dentin toward the pulp, and it gives it far more than enough time in a child.

A child’s tooth is the clearest case against waiting, given that measured progression through the same layers runs roughly three times faster in baby teeth. For adults, the honest answer is that some cavities do progress slowly over two years and some reach the nerve well inside that window. There is no way to know in advance which one you have, and the cost of guessing wrong is a root canal instead of a filling.

Which Teeth Usually Rot First?

Molars and premolars usually rot first, because the deep grooves and pits on their chewing surfaces trap food particles and plaque that a toothbrush cannot reach. Mayo Clinic notes that decay most often occurs in these back teeth for exactly that reason.

That reason also explains why sealants work so well on them. The CDC reports that dental sealants prevent 80% of cavities in permanent molars for the first two years after placement and continue to block about 50% of cavities for up to four years, simply by covering those grooves with a smooth protective coating.

Smooth surfaces are harder to attack, but they are not immune. Decay between teeth develops on the flat contact surfaces where floss reaches and brushes do not, and root decay develops on exposed root surfaces in patients with gum recession. Root surfaces have no enamel at all, only a thin layer of cementum, so they soften far more quickly than a crown surface does.

At What Age Do Teeth Start Rotting?

Teeth can start rotting as soon as they erupt, which means decay is possible in infancy. The CDC’s 2024 surveillance data found untreated decay in baby teeth affecting 18% of children aged 6 to 8 and 11% of children aged 2 to 5, and 57% of adolescents aged 12 to 19 have had cavities in their permanent teeth.

Permanent teeth stay at risk for life, and risk climbs again in later decades. The CDC recorded untreated decay peaking near 22% among adults aged 20 to 34, and roughly 13% of adults aged 65 and older carry untreated decay, often on exposed roots. Older adults also take more medications that dry the mouth, which removes saliva’s buffering effect exactly when root surfaces are most exposed.

What Organs Are Affected by Tooth Decay?

Tooth decay itself affects only the tooth, but an untreated infection that develops from it can spread to the jawbone, the sinus, the soft tissue of the face and neck, and in rare cases the bloodstream. Bloodstream involvement is uncommon, and it is the reason dentists treat facial swelling as urgent rather than routine.

Urgency at that point comes down to anatomy. Infection at a root tip first erodes the bone immediately around it. From there it can track into the soft tissue spaces of the face and under the jaw, which is where visible swelling appears. Swelling that pushes toward the floor of the mouth or the neck can begin to affect breathing and swallowing, and that situation belongs in a hospital emergency department rather than a dental chair.

A dental chair handles everything short of that line. Our office treats non life-threatening dental emergencies including urgent extractions, root canals, and incision and drainage, and patients who need an emergency dentist for severe toothache or a dental abscess can be seen quickly. Swelling accompanied by fever, or any difficulty breathing or swallowing, should go straight to the emergency room.

Can You Stop Tooth Decay When It Starts?

Yes, you can stop tooth decay when it starts, as long as the decay has not yet broken through the enamel surface. Enamel that has been weakened but not cavitated can take minerals back in through a process called remineralization.

Remineralization runs on fluoride, calcium, phosphate, and saliva. Fluoride is the accelerator, because it draws minerals back into the enamel lattice and rebuilds it in a form that resists acid better than the original. The CDC reports that fluoride varnish alone reduces cavities in baby teeth by about one-third, and the reversal figures from adult lesion studies show that most early lesions either heal or stall rather than progress.

Progression stalls faster when three things happen together: professional fluoride treatments, better plaque control at home, and fewer acid exposures across the day. The third one is the piece patients underestimate. Eating the same amount of sugar in one sitting does far less damage than spreading it across six snacking episodes, because each episode restarts the acid cycle.

Restarting the acid cycle repeatedly is also what hardened tartar does, since tartar shields bacteria from your toothbrush entirely. Regular dental cleanings remove that shield, and the polishing step leaves a surface plaque has a harder time gripping. Patients across Queens who come in twice a year rather than once tend to catch far more at the reversible stage.

What Is the Treatment for Tooth Decay?

The treatment for tooth decay depends on how deep it has reached: fluoride for early demineralization, a filling once a cavity forms, a crown when too much structure is lost, root canal therapy when the pulp is infected, and extraction when the tooth cannot be saved. Each step up that ladder removes more tooth, which is the practical case for coming in early.

Coming in early keeps you at the lower rungs. Treatments run in this order from least to most involved:

1. Fluoride treatment. Applied in the office for early lesions that have not broken the enamel surface, sometimes paired with prescription-strength toothpaste at home.
2. Composite filling. The decayed portion is removed under local anesthesia and the space is rebuilt in layers with tooth-colored resin, then hardened, shaped, and polished.
3. Dental crown. Used when decay has taken so much structure that a filling would not hold, a crown covers the entire tooth and restores its strength.
4. Root canal therapy. The infected pulp is removed, the canals are cleaned and disinfected, and the tooth is sealed, usually followed by a crown for support.
5. Extraction and replacement. Reserved for teeth too damaged to restore, with a bridge, denture, or implant discussed afterward to fill the space.

Deciding between the second and third rung comes up often, and the choice turns on how much healthy tooth remains around the decay rather than on the size of the hole alone. Choosing a crown or filling comes down to whether enough sound structure remains to support a restoration from the inside.

Sound structure is present in most cases we see, because most decay still arrives at the filling stage. Composite fillings remain the most common restorative procedure in the practice, and they preserve more of the natural tooth than any later option does.

When Should You See a Dentist About Tooth Decay?

You should see a dentist every six months for routine detection, within about a week if sensitivity or a dark spot has appeared, and the same day if you have severe pain, pain when chewing, or any swelling in your face or gums. These three tiers cover nearly every situation a patient runs into.

Schedule a Regular Visit

Book a preventive exam and cleaning at least every six months, which is the interval the American Dental Association recommends. This visit exists to catch decay before it ever produces a symptom, using x-rays that reveal decay between teeth and under old fillings where nothing is visible to the eye. At our Flushing office, a checkup exam also includes an oral cancer screening and a check of the gums.

Book an Appointment Soon

Call within the next week if sensitivity to hot, cold, or sweet has lasted more than a few days, if a dark or chalky spot has appeared on a tooth, if floss shreds or tears on the same rough edge every time, or if food packs into one specific gap after meals. None of these is an emergency, and all of them mark the window where restorative care is still simple. Waiting for these signs to turn into pain is what turns a filling into something larger.

Seek Same-Day Care

Call immediately if you have severe or persistent pain, pain that wakes you at night, pain when chewing or biting down, or swelling in your face, jaw, or gums. A foul taste that keeps returning belongs in this group too, since it often signals a draining infection.

One boundary matters here. Swelling that comes with a fever, or any difficulty breathing or swallowing, needs a hospital emergency department rather than a dental office, and going straight there is the right call.

Frequently Asked Questions

Does Tooth Decay Always Hurt?

Tooth decay does not always hurt, and early decay almost never does. Pain begins only once decay reaches the dentin or pulp, which means a cavity can exist for months or years without producing any sensation. Mayo Clinic notes that a beginning cavity often causes no symptoms at all, which is why detection relies on exams and x-rays rather than on how a tooth feels.

Can a Cavity Be Seen on an X-Ray Before You Can See It?

Yes, a cavity can be seen on an x-ray well before it is visible in the mouth. X-rays show decay between teeth and beneath existing fillings, which are the two locations self-examination cannot reach. This is why routine radiographs are taken at preventive visits even when a patient reports no problems.

What Is the Difference Between a Cavity and a Stain?

The difference between a cavity and a stain is depth and pattern. Stains sit on the enamel surface, feel smooth, and usually affect several teeth at once from coffee, tea, or tobacco. A cavity is generally darker, concentrated in one spot on one tooth, and often feels rough or catches a floss thread. A single dark point on a single tooth is far more likely to be decay than staining.

Do Sealants Prevent Tooth Decay?

Sealants prevent a large share of tooth decay on back teeth. The CDC reports that dental sealants block 80% of cavities in permanent molars during the first two years after placement and continue to prevent about 50% of cavities for up to four years. Sealants work by covering the deep grooves on chewing surfaces where food and plaque collect.

Can Dry Mouth Cause Tooth Decay?

Yes, dry mouth causes tooth decay by removing saliva’s protective role. Saliva rinses away food particles, neutralizes acid, and delivers the calcium and phosphate that rebuild weakened enamel. When saliva flow drops, whether from medication, a medical condition, or radiation treatment to the head and neck, decay accelerates noticeably.

Why Does a Toothache Sometimes Stop Hurting on Its Own?

A toothache sometimes stops hurting because the pulp tissue inside the tooth has died and can no longer transmit pain. This is not recovery. Bacteria remain active inside the tooth and usually go on to form an abscess at the root tip, so a tooth that hurt badly and then went quiet still needs evaluation.

Is Tooth Decay Common Worldwide?

Tooth decay is the most common chronic disease in the world. World Health Organization figures from the Global Burden of Disease data put roughly 2 billion people living with untreated decay in permanent teeth, alongside about 514 million children with untreated decay in baby teeth. The National Institute of Dental and Craniofacial Research describes it as the most common chronic disease in both children and adults in the United States, even though it is largely preventable.

The Bottom Line

Tooth decay announces itself in a sequence. Nothing at all in the beginning, then white or chalky spots, then sensitivity to hot, cold, and sweet, then visible pits and darkening, then constant pain, and finally swelling, foul taste, and fever once infection sets in. Where you are in that sequence decides whether the answer is a fluoride treatment, a filling, a crown, or a root canal, and the gap between the first item and the last one is usually measured in years rather than weeks.

Years of margin only help if someone is looking. Roughly 1 in 5 adults is walking around with untreated decay right now, and most of them feel fine, because early decay is silent by design. Six-month exams and x-rays exist precisely to close that blind spot, and the research on early lesions shows that most of them reverse or stall when they are found in time.

If something on your teeth has changed recently, a spot, a sensitivity that will not settle, or floss that keeps catching in one place, we are glad to take a look and tell you exactly what stage it is at. You can reach Avalon Dental at (347) 472-0318, or contact us online to schedule a visit.