Cavities don’t always announce themselves with pain. In the earliest stage, you might not feel anything at all. The first clue is often visual: a small, white, chalky spot on the surface of a tooth where minerals are starting to break down. As decay progresses, the signs become harder to ignore, moving from mild sensitivity to persistent pain. Nearly 21% of adults between 20 and 64 have at least one untreated cavity right now, so if you suspect you have one, you’re far from alone.
What a Cavity Looks Like
The earliest visible sign of decay is a small white spot on your tooth enamel. This isn’t a cavity yet. It’s demineralization, meaning the outer layer of your tooth is losing minerals faster than it can rebuild them. At this stage, the damage can actually be reversed with fluoride.
If the decay continues, that white spot darkens to a light brown, and a small hole may form in the enamel. This is a true cavity. As it deepens into the softer layer beneath the enamel, the discoloration turns a darker brown. In advanced stages, the spot can appear nearly black. You might also notice a rough or jagged edge when you run your tongue over the tooth, or food may get stuck in a spot that never used to trap anything.
Not all cavities are easy to see. Decay between teeth or along the gumline can be completely invisible to you, which is one reason dental X-rays exist. Bitewing X-rays, the kind where you bite down on a small tab, are specifically designed to reveal cavities hiding between teeth.
How a Cavity Feels
In the early stages, a cavity often feels like nothing. That’s part of the problem. The outer enamel doesn’t contain nerves, so decay can eat through it without triggering any sensation.
Once the decay reaches the dentin, the softer layer beneath the enamel, things change. Dentin contains tiny tubes that connect to the tooth’s nerve, so you’ll start noticing sensitivity. Hot coffee, ice water, or sweet foods may cause a brief, sharp sting that wasn’t there before. This is different from generalized tooth sensitivity (which tends to affect multiple teeth): cavity-related sensitivity usually shows up in one specific tooth.
As the decay deepens further and reaches the pulp, the living tissue at the center of the tooth, pain can become more constant and intense. The pulp swells, but there’s nowhere for it to expand inside the rigid tooth structure. That pressure on the nerve produces a throbbing ache that can come on spontaneously, not just when you eat or drink. Pain when you bite down is another telltale sign that decay has progressed significantly.
Signs That Point to Something More Serious
If a cavity goes untreated long enough, bacteria can push past the pulp and cause an abscess, a pocket of infection at the root of the tooth. An abscess brings a different level of pain: severe, often radiating into the jaw or ear. You might also notice swelling in your gums, face, or jaw, along with fever or swollen lymph nodes in your neck. This is an infection that won’t resolve on its own and needs prompt treatment.
Cavity vs. Normal Sensitivity
Plenty of people have sensitive teeth without having a cavity. Worn enamel from aggressive brushing, receding gums, or acidic diets can all make teeth react to temperature. The key differences to watch for:
- Location: Cavity pain tends to be localized to one tooth. General sensitivity usually affects several teeth, often along the gumline.
- Triggers: Sensitivity from a cavity responds to sweets in addition to hot and cold. Plain temperature sensitivity rarely reacts to sugar.
- Progression: General sensitivity stays relatively stable over time. Cavity pain gets worse, because the decay is actively growing.
- Visible changes: If you can see a dark spot, a hole, or discoloration on the sensitive tooth, that points toward decay rather than general sensitivity.
What You Can’t Detect at Home
Self-checks have real limits. Cavities between teeth, beneath old fillings, or just below the gumline are essentially invisible without dental imaging. Your dentist uses a combination of visual examination, a thin instrument called an explorer to probe for soft spots, and bitewing X-rays to catch what your eyes and tongue can’t. Many cavities are discovered during routine checkups in people who had no symptoms at all.
What Happens Once a Cavity Is Confirmed
Treatment depends entirely on how far the decay has spread. If it’s caught at the white-spot stage, before a hole has formed, a professional fluoride treatment can help the enamel remineralize and potentially reverse the damage entirely. These treatments use a much higher concentration of fluoride than what’s in your toothpaste.
Once an actual hole has formed, a filling is the standard fix. Your dentist removes the decayed material and fills the space with composite resin, porcelain, or another material. It’s a straightforward procedure, and the tooth functions normally afterward.
If the decay is extensive enough that the remaining tooth structure is weakened, a crown may be needed. This is a custom-fitted cap that covers the entire visible portion of the tooth, protecting it from fracture. When decay has reached the pulp and caused infection or significant pain, a root canal removes the damaged tissue from inside the tooth and seals it. If the tooth is too far gone for any of these options, extraction becomes the last resort.
The earlier you catch it, the simpler and less expensive the fix. A small filling is a very different experience from a root canal, both in the chair and in the bill afterward. If you’re noticing any of the signs above, particularly sensitivity to sweets, a visible spot, or pain in a single tooth, those are strong reasons to schedule an exam sooner rather than later.