A cavity rarely announces itself. In the early stages there is usually no pain at all, which is why so many people only discover tooth decay once it has already reached the inner layers of the tooth. Knowing what a cavity looks like — and what it feels like as it progresses — helps you catch problems while they are still small, simple and affordable to fix.
In this guide, the team at Dentistry On Bay in downtown Toronto explains the early signs of a cavity, how to tell a cavity from a harmless stain, and when it is time to book a dental exam.
Quick Answer: What Does a Cavity Look Like?
An early cavity usually looks like a chalky white or dull spot on the enamel. As decay progresses, the spot can turn light brown, dark brown or black, and eventually forms a visible hole or pit in the tooth. Cavities most often appear on the chewing surfaces of back teeth, between teeth, and along the gumline — places that are hard to see in a mirror, which is why regular dental exams and X-rays matter.
The Stages of a Cavity (and How Each One Looks)
Stage 1: White Spots (Early Demineralization)
The first visible sign of an early cavity is a matte, chalky white patch on the tooth surface. This happens when acids from plaque bacteria start pulling minerals out of the enamel. At this stage the damage can often be stopped or even reversed with fluoride, better brushing and flossing, and fewer sugary snacks.
Stage 2: Enamel Decay
If demineralization continues, the enamel begins to break down. The white spot may darken to a light brown colour and the surface can feel slightly rough. Once the enamel structure is lost, it cannot grow back — a small tooth-coloured filling is usually needed.
Stage 3: Dentin Decay
Beneath the enamel is dentin, a softer layer that decays faster. Cavities at this stage often look like a brown or dark spot with a visible pit, and many people start to notice sensitivity to sweets, cold or hot drinks. Treatment is still typically a filling, sometimes a larger one.
Stage 4: Pulp Involvement
When decay reaches the pulp — the nerve and blood vessels inside the tooth — it can cause lingering or throbbing pain, swelling, or pain when biting. At this point a tooth may need root canal therapy and often a crown to protect what remains.
Stage 5: Abscess
An untreated infection can form an abscess at the root tip. Signs include facial or gum swelling, a pimple-like bump on the gum, a bad taste, or fever. This is a dental emergency — call your dentist right away.
Cavity vs. Stain: How to Tell the Difference
Not every dark mark on a tooth is decay. Coffee, tea, red wine and smoking can all leave surface stains. Some general differences:
- Stains are usually smooth, spread across several teeth, and often lighten after a professional cleaning.
- Cavities tend to be localized to one spot, may feel rough or catch floss, and can be sensitive to sweets or temperature.
- Dark grooves on the chewing surfaces of molars may be stained fissures or early decay — only an exam (and sometimes an X-ray) can tell for sure.
Because the two can look alike, the safest approach is to have any new or changing spot checked during your next dental exam.
What Does a Cavity Feel Like?
Early cavities often feel like nothing at all. As decay deepens, you might notice:
- A twinge when eating sweets or drinking something cold
- Food repeatedly getting stuck in the same spot
- Floss shredding or catching between two teeth
- A rough edge or small hole you can feel with your tongue
- Pain when biting down, or a dull ache that comes and goes
Pain that lingers, wakes you up at night, or comes with swelling is a sign the decay may be close to the nerve.
How to Tell If You Have a Cavity at Home
You can do a quick self-check in good light with a small mirror: look for white chalky spots, brown or black marks, or visible pits — especially on back teeth and near the gumline. That said, many cavities form between teeth or under existing fillings and are invisible without a dental X-ray. A home check is a helpful early warning, not a replacement for a professional exam.
How Cavities Are Treated
- Early white spots: fluoride treatment, improved home care and diet changes.
- Small to moderate cavities: a tooth-coloured composite filling, usually completed in a single visit.
- Large cavities: an inlay, onlay or dental crown to restore strength.
- Decay reaching the nerve: root canal therapy followed by a crown.
The earlier a cavity is found, the smaller — and less costly — the treatment tends to be.
How to Prevent Cavities
- Brush twice a day for two minutes with fluoride toothpaste.
- Clean between your teeth daily with floss or interdental brushes.
- Limit frequent snacking and sipping on sugary or acidic drinks.
- Drink water after meals, especially if you can’t brush.
- Book regular dental cleanings and exams so problems are caught early.
- Ask about sealants and fluoride for children’s molars.
Cavity Checks and Fillings in Downtown Toronto
If you’ve spotted a suspicious mark or have new sensitivity, the team at Dentistry On Bay can take a look. Our clinic is located at 790 Bay St., Suite 1020, Toronto, ON M5G 1N8, near Bay and College and a short walk from College Station. We welcome new patients, families and CDCP patients.
Request an appointment or call 416-924-0437.
Frequently Asked Questions
- What does an early cavity look like?
- An early cavity usually appears as a chalky white or dull spot on the enamel. It is often painless and can sometimes be reversed with fluoride and better home care if caught early.
- Can a cavity go away on its own?
- A very early white-spot lesion can remineralize with fluoride and good hygiene, but once the enamel has broken down into a hole, it cannot heal on its own and needs to be treated by a dentist.
- Are brown spots on teeth always cavities?
- No. Brown spots can be surface stains from coffee, tea or tobacco. Cavities are more likely if the spot is in one location, feels rough, or is sensitive. A dental exam is the only way to know for sure.
- Do cavities always hurt?
- No. Most cavities don’t hurt in the early stages. Pain usually starts once decay reaches the dentin or the nerve, which is why regular checkups are important.
- How long does it take to fill a cavity?
- A routine filling typically takes about 20 to 60 minutes depending on the size and location of the cavity, and is usually completed in one visit.
- How often should I get checked for cavities?
- Most people benefit from a dental exam and cleaning every six months, though your dentist may recommend a different schedule based on your risk.
This article is for general information only and is not a substitute for a professional diagnosis. Please book an exam if you have concerns about your teeth.