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.
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.
- Brown or dark spot. Some brown spots are active decay; others are old, stopped (arrested) decay that is hard and shiny. Only an exam can tell.
- 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 can be polished off at a cleaning; 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.
What Does a Cavity Look Like on an X-Ray?
Many cavities — especially between teeth or under old fillings — can't be seen in the mirror and show up first on X-rays. On a dental X-ray, a cavity appears as a darker (radiolucent) area within the tooth. Healthy enamel and dentin appear light gray-to-white on an X-ray; decay, which is less dense than sound tooth structure, appears as a darker patch.
What to look for on a bitewing X-ray:
- A triangular dark shadow starting at the contact point between two teeth — the classic sign of an interproximal (between-teeth) cavity
- A dark area beneath a filling — a sign of secondary decay forming under old restorations
- A darker region spreading through the dentin toward the pulp in an advanced cavity
Dentists use bitewing X-rays (which show the crowns of upper and lower teeth side by side) to catch cavities at the stage when they are still small enough for a simple filling. This is one of the main reasons routine X-rays matter: a cavity that is too small to see or feel on exam appears clearly on film.
What Does a Cavity Look Like Between Teeth?
Between-teeth (interproximal) cavities are the most commonly missed type because you cannot see them in the mirror. They form on the contact surfaces where two teeth touch. From the outside, the tooth may look perfectly fine — no visible staining, no hole, no obvious damage. Bitewing X-rays are the main way to find them.
Signs that may hint at an interproximal cavity (though not always present):
- Food consistently getting trapped between two specific teeth
- Floss shredding, catching, or having a different feel in one spot
- Sensitivity in an area you cannot pinpoint to one tooth surface
- A very slight gray or dark tinge visible at the edge of the gum between teeth — only in advanced cases
By the time an interproximal cavity causes pain or becomes visible, it has usually reached the dentin or deeper. Catching it on a routine X-ray when it is still in the enamel means a smaller, less invasive filling and a lower cost.
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 usually show up first 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 at the interval your dentist recommends (every six months for many people): a cavity caught between teeth at the X-ray stage is a small filling. Left untreated, the same cavity can eventually reach the nerve and need 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 with the tooth. 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:
Once you've booked and returned your forms, we verify your benefits 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.
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 surface breaks down into a hole or soft spot, the decay won't reverse and a filling is usually needed. A brown or dark spot with a hard, intact surface may be stopped decay that can be watched or sealed.
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 matter, at the interval your dentist recommends (every six months for many people).
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 runs $145–$564 at Innova Smiles — smaller one- or two-surface fillings toward the low end, larger fillings toward the top. The top is our standard fee; the low end is what a patient whose plan covers the treatment typically pays before their share is applied.
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.
What does a cavity look like on an X-ray? On a dental X-ray, a cavity shows up as a dark shadow within the tooth — decay is less dense than healthy enamel and dentin, so it appears darker. A classic between-teeth cavity looks like a small triangular dark area at the contact point of two teeth on a bitewing X-ray. X-rays detect cavities that are invisible to the eye and too small to cause symptoms yet, which is why bitewing X-rays are repeated on a schedule set by your cavity risk. Under ADA/FDA guidance, that is as often as every 6–18 months for adults at higher risk and every 24–36 months for adults at low risk.
What does a cavity look like between teeth? Interproximal (between-teeth) cavities are invisible from the outside — the tooth surface may look completely normal in the mirror. They form on the hidden contact surfaces and are usually found on bitewing X-rays, where they show up as a dark triangular shadow at the tooth contact point. Subtle clues before a cavity becomes obvious: food trapping repeatedly between two teeth, floss shredding in one spot, or mild sensitivity you can't pin to one surface.
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.
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How our pricing works
Tooth-colored composite fillingOur fee range$145–$564 per tooth
- The fee covers the procedure as planned at your exam. Anything your case adds is written into your estimate before treatment, never after.
- If you have dental insurance, your plan pays us a negotiated fee for covered treatment — typically about half of our standard fee — and you pay your share of that lower amount. Once you've booked your appointment and returned your forms, we'll verify your insurance benefits and call you with a breakdown within three business days.
- 0% APR financing is available through Cherry, subject to credit approval.*
- No insurance? Our in-house membership plan (from $395/yr) includes your preventive care and takes a flat 20% off our standard fee for this treatment.
- The top of the range is our standard fee; the low end is what a patient whose plan covers the treatment typically pays before their share is applied.
- Your exact fee is confirmed in writing at your visit, after your exam and after we have checked your insurance, and we explain anything your plan may not pay before treatment.
- Patients aged 65 and older get 10% off all dental treatments. Mention it when booking and we'll apply it automatically.
*0% APR financing is through Cherry, a third-party lender, not Innova Smiles, and is subject to credit approval; not all applicants qualify. Plans run up to 24 months in equal payments, the first due at purchase. Cherry's 0% APR plans carry no deferred interest; if an account becomes delinquent, interest may apply going forward, never retroactively. Your cost and payment depend on your treatment plan and approved offer, and are confirmed in writing at your consultation.
Sources & Further Reading
- Cavities / Tooth Decay — ADA MouthHealthy
- Tooth Decay — National Institute of Dental and Craniofacial Research (NIDCR)
- Guideline on Prescribing Dental Radiographs (ADA/FDA selection criteria) — American Academy of Pediatric Dentistry
