Something feels off with one tooth. A twinge with iced coffee. A spot you noticed in the mirror. Floss that shreds in the same place every time. You want to know whether it's a cavity.
Here is the direct answer first, and then the part most articles on this leave out.
The four signs people notice: sensitivity to cold, heat or sweets that lingers; a toothache or pain when you bite; a white, brown or black spot; and a hole or rough edge you can see or feel.
The catch: all four tend to show up late. In its early stages a cavity usually causes no symptoms at all, and that is exactly when it is smallest and simplest to treat.
It's also common. The CDC's most recent national data found that about 1 in 5 adults ages 20 to 64 had at least one untreated cavity.
The four signs of a cavity, and what each one actually means
1. Sensitivity that lingers
Enamel has no nerves. Once decay gets through it into the dentin underneath, cold, heat and sugar can reach the nerve through tiny channels in the dentin. A quick twinge that fades the moment the cold is gone is common and has many possible causes. Pain that lingers after the cold is gone matters more: it can mean the nerve itself is inflamed. That one shouldn't wait.
2. A toothache, or pain when you bite
A constant ache, pain that wakes you up, or a sharp pain when you bite down usually means the problem is no longer small. Deep decay, an infection at the root and a cracked tooth can all feel like this, and they are not treated the same way. Pain on biting in particular is as likely to be a crack or a failing filling as a new cavity.
3. A white, brown or black spot
A chalky white patch, often near the gumline, is frequently the earliest visible stage: enamel that has lost mineral but hasn't broken down yet. Brown or black can be decay, or it can be harmless stain sitting in the grooves of a tooth. Color alone can't tell you which. That takes an exam, and often an X-ray.
4. A hole, a rough edge, or floss that keeps tearing
Once you can see or feel a hole, the surface of the tooth has broken down. Between the teeth you usually can't see anything. The clues there are indirect: food that packs into the same spot every time, or floss that frays or catches in one place. Food packed into a hole can even look like a white filling, as in the photos further down.
Why most cavities don't hurt until they're deep
Enamel is the hardest tissue in the body, and decay in enamel is silent. The dentin underneath is softer. Once decay reaches it, it tends to spread wider than the opening on the surface suggests. That is why a small dark spot can sit over a much larger cavity, and why for some people the first sign is a piece of tooth breaking off.
The places adults most often get cavities are also the places you can't see in a mirror: between the teeth, and under the edges of existing fillings and crowns. Those are found on X-rays and in an exam, not by symptoms.
Can a cavity go away on its own?
Only at the very first stage. An early lesion, the chalky white stage before the surface breaks, can sometimes harden again with fluoride, less frequent sugar and good cleaning. That is the one point where "watch it and change habits" is a legitimate plan, and it should be monitored by someone who can actually see it.
Once the surface has broken into a cavity, it does not heal. Brushing and flossing can slow it down. They can't put back tooth structure that is gone. Advice that a cavity can be brushed away is wrong.
Where adults actually get cavities
- Around older fillings and crowns. Decay starts at the edge where the restoration meets the tooth and works underneath it. It is often painless until a lot of tooth has been lost, because the filling hides it.
- On exposed root surfaces. When gums recede, the root is exposed. Root surface is softer than enamel and decays more easily, often right at the gumline. Gum health and decay risk are linked.
- With a dry mouth. Saliva is one of the main defenses against decay, and many common medications reduce it.
When this happens in one tooth, it's a filling. When decay is turning up under several older restorations at once, replacing them one at a time, as each one fails, is usually the least predictable way to handle it. Each repair gets planned around the last one rather than around how the teeth work together. That is when I step back and plan the whole mouth. Sometimes that becomes a full mouth rehabilitation. More often it's a phased plan that deals with the cause first and replaces work in a sensible order.
Have older fillings or crowns and wondering whether they're holding up? Send photos through the free Virtual Smile Consultation. In pain right now? Call (954) 722-9020.
What an evaluation for a cavity involves
I don't diagnose a cavity from a photo or a description of symptoms, and a look in the mirror misses most of them. I examine every surface, check the edges of existing fillings and crowns, and take bitewing X-rays to see between the teeth and under older work. If there is pain, I test how the tooth responds to cold and to biting, to separate a cavity from an inflamed or infected nerve or a crack. I also look at why the decay is happening: diet, dry mouth, recession and how well existing work fits. The treatment follows from what's found: monitoring and fluoride for an early enamel lesion, a filling for a small cavity, an onlay or crown when too much tooth is gone to hold a filling, and root canal treatment when the nerve is involved.
Signs you should have a tooth checked
Read this as a prompt to be evaluated, not a diagnosis:
- The same tooth has been sensitive to cold or sweets for more than a couple of weeks
- Pain lingers after something cold or hot is gone
- It hurts when you bite down, or when you release
- A chalky white, brown or black spot is new or getting bigger
- Food packs into the same spot, or floss tears there
- You can feel a rough edge, a chip, or a dark line around an old filling or crown
- There's a bad taste or smell coming from one area
- It has been more than a year since your last dental X-rays
Two or three together is a pattern, not a coincidence.
Don't wait on these. Swelling in the gum or face, a pimple-like bump on the gum, fever, or tooth pain that wakes you up: call the office the same day, or see our emergency dental care page.
Swelling that spreads toward the eye or down the neck, or any difficulty swallowing or breathing, is a medical emergency. Go to the emergency room.
Honest limits
Not every sensitive tooth has a cavity. Gum recession, worn enamel, grinding, whitening and cracks all cause sensitivity, and treating the wrong cause doesn't help.
A filling repairs the damage. It doesn't change why the decay happened. Without addressing the cause, new decay tends to show up next to the old.
Decay that reaches the nerve may need a root canal, and a tooth that can't be restored may need to come out. Where a case needs an endodontist or an oral surgeon, I refer. A restoration is not a substitute for treatment a tooth genuinely needs.
This article is about adult teeth. Individual results vary, and not every tooth or case is a candidate for any particular treatment.
Questions patients ask
Can you have a cavity and not feel it?
Yes. Most cavities cause no symptoms until they reach the dentin, and decay under an old filling or between the teeth can be painless for a long time. That is what routine exams and X-rays are for.
How fast does a cavity get worse?
It varies a lot. Decay tends to move slowly through enamel and faster once it reaches dentin, and frequent sugar or a dry mouth speeds it up. Nobody can predict it from the mirror, which is why a suspected cavity is worth having looked at rather than watched at home.
Why does a tooth that already has a filling hurt?
New decay under the edge of the filling, a crack, a filling that sits high in the bite, or an inflamed nerve. They feel similar and are treated differently, so it needs an exam.
Start with an exam, not a guess
I'm Dr. Rajvinder Dulay. I've practiced restorative dentistry and full mouth rehabilitation in Tamarac for more than 20 years. Many of the larger restorative cases I see started as small cavities that went unchecked for years. A small cavity found early is a small repair. The first step is finding out what's actually there.