7 Signs You Have a Cavity (Before It Gets Worse)

One of the earliest and most common signs of a cavity is sensitivity when eating or drinking something hot or cold. You might notice a sharp, sudden twinge when sipping iced water or biting into ice cream. This happens because decay has worn through your protective enamel, exposing the sensitive dentin layer underneath. The dentin contains microscopic tubes that lead to the nerve, allowing temperature changes to trigger pain.

Early cavity sensitivity is typically brief—lasting only a moment after the trigger is removed. If sensitivity lingers for minutes or longer, the decay may have progressed closer to the pulp.

2. Visible holes, pits, or dark spots

Sometimes you can actually see a cavity forming. Look for small holes or pits in your teeth, especially on the chewing surfaces of molars. Dark spots—brown, black, or sometimes chalky white—can indicate areas where decay is developing. White spots, called "white spot lesions," are actually the earliest visible sign of decay and represent areas where minerals are being lost from the enamel.

Use a mirror and good lighting to examine your teeth regularly, particularly in areas that are hard to reach with a toothbrush.

3. Pain when biting down

If you feel a sharp pain when you bite down on food, a cavity might be to blame. This happens when decay has weakened the tooth structure enough that pressure causes the remaining enamel to flex, stimulating the nerve underneath. The pain is often inconsistent—you might feel it with one bite but not the next, depending on exactly how your teeth come together.

This symptom can also indicate a cracked tooth, so it's important to have it evaluated regardless of the cause.

4. Sensitivity to sweet foods

Sugar sensitivity is a classic cavity symptom. When you eat something sweet—candy, soda, fruit, even some breads—and feel a sharp zing in a specific tooth, decay is often the culprit. Sugar draws fluid out of the dentin tubules through osmosis, creating a brief vacuum that triggers the nerve. A healthy, intact tooth with full enamel coverage doesn't react this way.

5. Food constantly getting stuck in the same spot

If food persistently catches in the same place between your teeth, it could indicate a cavity forming between the teeth (called an interproximal cavity). These cavities create rough surfaces and irregular gaps where food loves to hide. You might find yourself reaching for floss after every meal to clear the same spot.

Between-teeth cavities are particularly sneaky because you can't see them—they're only visible on dental X-rays.

6. Persistent bad breath or bad taste

Cavities harbor bacteria. As these bacteria multiply and feed on food particles trapped in the decay, they produce foul-smelling compounds. If you have persistent bad breath that doesn't improve with brushing, or you notice a consistently unpleasant taste in your mouth, a cavity might be the source.

Advanced cavities and those that have become infected are particularly likely to cause bad breath and a bitter or metallic taste.

7. A rough or sharp edge you can feel with your tongue

Run your tongue over your teeth. If you feel a rough patch, sharp edge, or area that just doesn't feel smooth anymore, the enamel may have broken down. Cavities create irregular surfaces as they eat away at tooth structure. Your tongue is surprisingly sensitive and can often detect textural changes before you see anything visually.

Early decay (enamel only) — $150-$250
At this stage, you might not even need a filling. Some early cavities can be reversed with fluoride treatments, improved hygiene, and dietary changes. If a filling is needed, it's small, quick, and requires minimal anesthesia.

Moderate cavity (into dentin) — $250-$400
Once decay reaches the dentin, a filling is definitely necessary. The procedure is still straightforward, but more drilling is required, and you'll likely need anesthesia for comfort.

Deep cavity (near the pulp) — $500-$800+
When decay gets close to the nerve, fillings become complex. You might need a build-up or an onlay instead of a simple filling. There's also risk that the tooth will need a root canal later.

Pulp involvement — $1,500-$4,000+
If decay reaches the pulp (nerve), you're looking at a root canal plus a crown. This involves multiple appointments, significant cost, and a tooth that will never be quite as strong as it was.

Tooth loss — $4,000-$6,000+ for replacement
If a cavity is left until the tooth can't be saved, extraction and replacement with an implant or bridge is the most expensive outcome of all.

The progression from early cavity to extraction can happen over months or years, but it only goes in one direction. There's no scenario where waiting makes things better or cheaper.

The cavity formation process:
Bacteria in your mouth feed on sugars and starches from the foods you eat. As they digest these carbohydrates, they produce acids as a metabolic byproduct. These acids dissolve the minerals in your tooth enamel—a process called demineralization.

Your saliva naturally helps remineralize your teeth by depositing calcium and phosphate back into the enamel. However, if acid attacks happen too frequently (from frequent snacking, sipping sugary drinks, or poor oral hygiene), demineralization outpaces remineralization, and a cavity begins to form.

Risk factors for cavities:

• Frequent snacking or sipping sugary/acidic drinks


• Dry mouth (reduced saliva means less natural protection)


• Not using fluoride toothpaste


• Inadequate brushing and flossing


• Deep grooves in teeth that trap bacteria


• Receding gums that expose tooth roots


• Old fillings with rough edges or gaps

While waiting for your appointment:
Continue your normal oral hygiene routine, paying extra attention to the suspicious area. Brush gently but thoroughly twice daily with fluoride toothpaste. Floss daily, especially around the tooth in question. Consider using a fluoride mouthwash for additional protection.

Avoid excessive sugar and acidic foods, which accelerate decay. If you have sensitivity, you might temporarily avoid very hot or cold foods on that side.

What to expect at your dental visit:
Your dentist will perform a visual examination, looking for visible signs of decay. They'll likely take X-rays, which reveal cavities between teeth and under old fillings—areas you can't see yourself. Using an explorer (the hooked metal instrument), they'll gently probe suspicious areas to check for soft spots that indicate decay.

If a cavity is found, your dentist will discuss treatment options. For most cavities, this means a filling—a straightforward procedure that can usually be completed in one visit.