A hole in your tooth is a cavity, and it will keep getting bigger if left alone. What starts as invisible mineral loss on the tooth’s surface eventually breaks through into deeper layers, causing pain, infection, and potentially tooth loss. About 21% of American adults between 20 and 64 have at least one untreated cavity right now, making this one of the most common health problems people walk around with.
How the Hole Forms
Your mouth is home to bacteria that feed on sugars and starches from the food you eat. As they break down these sugars for energy, they produce acid as a byproduct. That acid strips calcium and other minerals from the hard outer shell of your tooth, a process called demineralization. Over time, the weakened surface collapses inward, creating a physical hole.
Before the hole appears, you’ll often have what dentists call a “white spot lesion,” a chalky, discolored patch where minerals have started to leach out but the surface hasn’t broken yet. At this stage, the damage can actually reverse itself with fluoride, good brushing habits, and saliva (which naturally deposits minerals back onto teeth). Once the surface breaks and a true hole forms, that window closes. The damage is permanent and needs professional repair.
What Happens as It Gets Deeper
A tooth has three main layers: the hard outer enamel, a softer middle layer called dentin, and the innermost pulp, which contains the nerve and blood supply. The hole works its way through these layers in sequence, and each stage feels different.
There’s no universal timeline for how fast this happens. In most cases, cavities develop over the course of years. But with poor oral hygiene or a high-sugar diet, they can progress in months. Once decay reaches dentin, it tends to accelerate because dentin is softer and more porous than enamel.
Enamel Stage
When the hole is still limited to enamel, you typically won’t feel anything at all. Enamel has no nerve endings. You might notice a small dark spot or rough area with your tongue, but many people have no idea anything is wrong. This is one reason regular dental checkups matter: X-rays catch cavities you can’t feel yet.
Dentin Stage
Once the hole reaches dentin, sensitivity kicks in. You’ll likely notice a sharp twinge when eating something sweet, cold, or acidic. The pain tends to come on quickly and fade within a few seconds once the trigger is removed. Food may start getting stuck in the hole, and you might see a visible brown or black spot.
Pulp Stage
When bacteria push through dentin and reach the pulp, things escalate. The nerve inside the tooth becomes inflamed, a condition called pulpitis. Early on, you’ll feel sensitivity to heat or cold that lingers for more than a few seconds, often as a throbbing or aching pain. If the inflammation gets severe enough, you may feel pain even without any trigger, including pain that wakes you up at night. Tapping on the tooth will hurt.
If the nerve tissue dies entirely, the sensitivity to temperature may actually disappear, which some people mistake for the problem resolving itself. It hasn’t. The infection is still progressing, and bacteria are now moving beyond the tooth into the surrounding jawbone and soft tissue.
What an Untreated Hole Leads To
Left long enough, bacteria from the dead pulp spill out the bottom of the tooth’s root and form a pocket of pus in the jawbone: a dental abscess. You may notice swelling in your gum, face, or jaw, a foul taste in your mouth, and pain that radiates to your ear or neck. Some people develop a fever.
A dental abscess is not something that resolves on its own. The infection can spread into the soft tissues of the face and neck (a condition called cellulitis) or, in rare but serious cases, reach the bloodstream. Bacteria originating in the mouth can travel through the bloodstream and contribute to inflammation elsewhere in the body. Research has linked chronic oral infections to cardiovascular problems, respiratory infections, difficulty controlling blood sugar in people with diabetes, and complications during pregnancy. Women with significant gum and tooth infections are up to six times more likely to deliver prematurely.
How Dentists Fix It
The treatment depends entirely on how deep the hole goes. The earlier you go in, the simpler and cheaper the fix.
- Filling: For decay that’s still in the enamel or dentin, the dentist removes the damaged portion and fills the space with a material that restores the tooth’s shape. This is the most common treatment. The procedure typically takes 20 to 60 minutes, and you can eat normally once the numbness wears off. Modern tooth-colored composite fillings actually have a slightly lower failure rate than the older silver-colored amalgam type, with about 3% of composite fillings failing per year compared to about 3.5% for amalgam.
- Crown: If the cavity has destroyed too much tooth structure for a filling to hold, a crown covers the entire visible portion of the tooth. Think of it as a custom-fitted cap. This requires two visits in most cases: one to shape the tooth and take impressions, another to cement the final crown.
- Root canal: When infection has reached the pulp, the dentist or a specialist removes the infected nerve tissue from inside the tooth, cleans and seals the internal canals, then typically places a crown on top. Despite its reputation, modern root canal treatment feels similar to getting a filling. Recovery involves a few days of mild soreness.
- Extraction: If the tooth is too far gone to save, it needs to come out. Less than 1% of filled teeth eventually need extraction, but teeth that go untreated for years are a different story. Replacing a missing tooth with an implant or bridge is significantly more expensive and involved than any of the earlier interventions.
How Long Fillings Last
A large-scale study tracking over 668,000 dental restorations found that single-surface composite fillings fail at a rate of about 2.6% per year, meaning the vast majority last well beyond five years. Fillings that cover more of the tooth’s surface tend to fail faster, with large fillings (covering four or five surfaces) failing at closer to 4.8% per year. When fillings do fail, the most common outcome is simply needing a replacement filling. About 2.3% of composite fillings eventually lead to root canal treatment, and only 0.4% lead to extraction.
The location matters too. Fillings on molars, which bear the heaviest chewing forces, fail slightly more often than those on premolars. Grinding your teeth at night, chewing ice, or eating a diet high in acidic foods can all shorten a filling’s lifespan.
Signs You Shouldn’t Ignore
Some cavities give you obvious warnings. Others don’t. Here’s what to watch for:
- Sensitivity to sweets or cold that fades quickly: This typically means the decay has reached dentin but the nerve is still healthy. A filling will likely solve it.
- Sensitivity to heat, or cold sensitivity that lingers: This suggests the nerve is becoming inflamed. The longer the pain lingers after the trigger is removed, the more likely you’ll need more than a filling.
- Spontaneous pain with no trigger: Pain that shows up on its own, especially throbbing pain at night, points to advanced nerve inflammation or infection.
- Swelling, pus, or a bad taste: These are signs of abscess. The infection has moved beyond the tooth itself.
- A tooth that suddenly stops hurting after weeks of pain: This can mean the nerve has died. The infection is still there and still spreading.
The difference between a $200 filling and a $3,000 crown-and-root-canal combination often comes down to a few months of waiting. If you suspect you have a hole in your tooth, the math strongly favors getting it looked at sooner rather than later.