Featured Answer: What does a cavity look like?
A cavity usually goes through visible stages. It often begins as a chalky white spot where the enamel is losing minerals, then darkens to a brown or black stain as the decay deepens, and finally forms a visible hole or pit you can see in the mirror or feel with your tongue. Advanced decay can leave a tooth looking gray or cause a piece to break off.
| Stage | What it looks like | Can it reverse? |
|---|---|---|
| White spot (early) | Dull, chalky white patch on enamel | Sometimes — with fluoride + hygiene |
| Brown/black stain | Discolored spot, decay into the enamel | No — needs a filling |
| Visible hole or pit | A dark hole you can see or feel | No — needs a filling |
| Deep decay | Gray tooth, broken piece, pain | May need a crown or root canal |
Here's the catch: many cavities are invisible. Decay between teeth or inside molar grooves can't be seen at all and is found only on a dental exam and X-rays.
Not sure about a spot on your tooth? Call (508) 481-0110 or book an exam at our Marlborough office for a clear answer.
The Visual Stages of a Cavity
Tooth decay is a process, not a single event. Catching it early changes everything about the treatment:
- White spot lesion (earliest). Acid from plaque pulls minerals out of the enamel, leaving a dull white patch — often near the gumline or around braces. This is the one stage that can sometimes be reversed with fluoride and better hygiene before any hole forms. See our deep dive on white spot lesions.
- Enamel decay (brown/black stain). Once the surface breaks down, the spot darkens. The tooth doesn't usually hurt yet, which is why people miss it.
- Dentin decay (hole forms). Decay reaches the softer dentin underneath and spreads faster. You may notice a hole, food trapping, or sensitivity to sweets, hot, or cold.
- Deep decay (toward the nerve). Left untreated, decay reaches the pulp, causing a toothache or infection that needs a root canal.
Cavity or Just a Stain? How to Tell
Not every dark mark is decay. Surface stains from coffee, tea, or tobacco sit on top of the enamel and wipe away or polish off; a cavity is a soft, broken area in the tooth structure. Likewise, a white spot can be an early cavity — or harmless fluorosis or an enamel defect. The only reliable way to tell is a clinical exam, where a dentist checks whether the area is soft, catches an explorer, or shows up on an X-ray.
Where Cavities Hide (and Why Exams Matter)
The cavities you can see are the easy ones. The dangerous ones hide:
- Between teeth, where a toothbrush and even the mirror can't reach — these only show on bitewing X-rays.
- In the deep grooves of back molars.
- Under the gumline or at the edge of an old filling or crown.
This is the whole argument for routine exams and cleanings every six months: a cavity caught between teeth at the X-ray stage is a small filling. The same cavity found a year later — after it has reached the nerve — can mean a root canal and a crown, at many times the cost.
What Happens When a Cavity Needs a Filling
Once decay has broken through the enamel, the tooth needs a filling. The visit is straightforward: the area is numbed with local anesthetic, the decayed portion is gently removed, and the space is filled — at Innova Smiles we use tooth-colored composite so the repair blends in and no one can tell. Most simple fillings are done in a single visit, and modern anesthesia keeps the appointment comfortable.
How Much Does a Cavity Filling Cost?
A tooth-colored composite filling generally runs:
| Filling size | Typical cost | CDT code |
|---|---|---|
| 1 surface | $150-$250 | D2391 |
| 2 surfaces | $200-$300 | D2392 |
| 3+ surfaces | $250-$450 | D2393 / D2394 |
Most dental insurance covers fillings at 70-100% as a basic service. We verify your benefits, file the claim, and give you a written estimate before any treatment. See insurance & financing for details.
When a Cavity Is Too Big for a Filling
If decay has destroyed too much of the tooth, a filling won't hold and the tooth needs more support:
- A crown when a large portion of the tooth is gone.
- A root canal when decay has reached the nerve and caused infection.
- In rare cases where the tooth can't be saved, an extraction and replacement.
Acting at the white-spot or small-cavity stage is how you avoid all of this.
Preventing the Next Cavity
Cavities are largely preventable. The essentials: brush twice daily with fluoride toothpaste, clean between your teeth, cut back on frequent sugar and acidic drinks, and keep up routine cleanings. For the full playbook, read how sugar damages teeth and our sugar, candy & cavity prevention guide.
Frequently Asked Questions
What does a cavity look like in the early stages? The earliest cavities look like a dull, chalky white spot on the enamel — a sign the tooth is losing minerals before any hole forms. At this stage decay can sometimes be halted or remineralized with fluoride and better hygiene. Once the spot turns brown or black, the decay has progressed into the tooth and a filling is usually needed.
Can you see a cavity yourself, or do you need a dentist? You can often see advanced cavities — brown/black staining or a visible hole — but many cavities form between teeth or in the grooves of molars where they're invisible to the eye. Those are caught only with a clinical exam and X-rays, which is why routine dental exams every six months matter.
Does a cavity always need a filling? Not always. A very early white-spot lesion can sometimes be remineralized with fluoride rather than drilled. But once decay breaks through the enamel into the softer dentin, it cannot heal on its own and needs a filling.
How much does a cavity filling cost? A tooth-colored composite filling typically costs about $150-$300 for a one- or two-surface filling and $250-$450 for a larger filling. Most dental insurance covers fillings at 70-100% as a basic service.
Is a white spot on my tooth a cavity? A white spot can be an early cavity, but white spots also come from fluorosis, old braces, or enamel defects — not all are decay. A dentist can tell the difference and may be able to remineralize an early lesion before it becomes a hole.
Get a Straight Answer About That Spot
If you've noticed a white, brown, or dark spot — or a tooth that catches food or feels sensitive — don't wait for it to hurt. Call (508) 481-0110 or book an exam. We'll check it, X-ray if needed, and tell you honestly whether it's a stain, an early spot we can watch, or a cavity that needs a filling.
Related Articles
- White Spots on Teeth: Causes and Treatment
- Sensitive Teeth: Causes and Treatment
- How Sugar Really Damages Your Teeth
Related Services
Sources & Further Reading
- ADA MouthHealthy — Cavities / Tooth Decay
- NIDCR — Tooth Decay
Sources & Further Reading
- Cavities / Tooth Decay — ADA MouthHealthy
- Tooth Decay — National Institute of Dental and Craniofacial Research (NIDCR)
