A cavity can look like a white chalky spot, a dark brown or black pit, or a visible hole in the tooth, depending on how far the decay has progressed. In its earliest stage, it’s easy to miss entirely. By the time most people notice something, the decay has usually moved past the surface enamel and into deeper layers of the tooth.
The Earliest Stage: White Spots
Before a cavity becomes a hole, it starts as a patch of weakened enamel called a white spot lesion. These spots look opaque and chalky compared to the surrounding tooth, and they lose the natural shine healthy enamel has. The mineral loss makes the enamel more porous, which scatters light differently and creates that flat, matte white appearance.
White spot lesions are tricky because they’re often only visible after the tooth surface has been dried. In a wet mouth, they can be nearly invisible. They tend to form near the gum line or around orthodontic brackets, anywhere plaque builds up and sits against the tooth for extended periods. At this point, the surface of the enamel is still intact. No hole has formed yet, and with good oral hygiene and fluoride, these spots can actually remineralize and reverse.
What Active Decay Looks Like
Once the enamel breaks down enough to create an actual hole, you’ve crossed into true cavitation. At first, this might be a tiny pit you can barely see but can catch with your tongue. The color shifts from white to light brown as the decay reaches the softer layer beneath the enamel, called dentin. Active, progressing decay in dentin is typically light brown and feels soft if touched with a dental instrument.
As the cavity grows, the discoloration deepens. Spots on the tooth turn brown, dark gray, or black. The hole gets larger and may become visible when you look in a mirror or feel it clearly with your tongue. Some cavities appear as dark shadows beneath the surface of the enamel, particularly when the decay has spread into the dentin underneath while the outer shell of enamel remains partially intact. This shadow effect can make the tooth look grayish or bluish in a specific area.
Long-standing decay that has slowed or stopped (sometimes called arrested decay) looks different from active decay. It turns very dark brown or black and feels hard and firm rather than soft. A dark spot that’s hard to the touch may be old damage that has stabilized, while a lighter brown spot that feels sticky or soft is more likely active and still spreading.
Cavities Between Teeth
Some of the hardest cavities to spot are the ones that form between teeth, where two tooth surfaces press together. These rarely show obvious signs until they’ve grown significantly. You won’t see a clear hole because the decay is hidden in the contact area. What you might notice is a dark shadow visible through the enamel when you look at the tooth from the front, or a grayish discoloration along the edge where the teeth meet.
More often, cavities between teeth announce themselves through sensation rather than appearance. You might feel a sharp sting when something sweet touches the area, or notice sensitivity to hot and cold drinks that wasn’t there before. Floss may catch or shred in the spot. Dentists typically find these cavities on X-rays during routine exams, since the visual signs are subtle enough that even a careful look in the mirror won’t reveal them.
Stain or Cavity: How to Tell the Difference
Not every dark spot on a tooth is a cavity. Coffee, tea, red wine, and tobacco all leave stains that can look alarming. A few differences help separate harmless staining from actual decay:
- Distribution: Staining tends to affect larger areas or multiple teeth at once. A cavity is usually a single, localized spot on one tooth.
- Persistence: Stains can lighten or shift after a cleaning or whitening. A dark spot from decay doesn’t come and go. It stays, and it grows over time.
- Texture: Stains sit on a smooth, intact surface. A cavity eventually creates a rough area, pit, or hole you can feel.
- Symptoms: Stains don’t hurt. If a discolored spot comes with sensitivity to temperature, pain when biting, or aching that worsens over time, that points toward decay.
What Cavities Look Like in Children
Cavities in baby teeth follow a distinctive pattern, especially in toddlers who fall asleep with a bottle or sippy cup. The decay typically hits the upper front teeth first, starting as a white band of demineralization right along the gum line. Parents often miss this stage because the white blends in with the tooth and the child isn’t complaining of pain.
If it progresses, those white bands turn into brown or black rings that wrap around the necks of the teeth like a collar. In severe cases, the visible portion of the upper front teeth can be destroyed entirely, leaving only brownish root stumps at the gum line. Meanwhile, the lower front teeth often remain completely healthy. This happens because the tongue covers and protects the lower teeth during feeding, while saliva from glands near the lower jaw continuously washes over them. The upper teeth get the most direct contact with milk or formula and the least natural rinsing.
The upper and lower molars are also common targets in young children, since their biting surfaces have natural grooves where bacteria settle easily.
The Six Stages Dentists Use
Dentists classify cavities on a scale from 0 to 6 using a standardized detection system. Knowing where your cavity falls on this scale gives you a clearer picture of what you’re dealing with:
- Stage 0: Sound, healthy tooth. No visible changes.
- Stage 1: First visible change in the enamel. This is the faint white spot you’d only see on a dried tooth.
- Stage 2: A more obvious change in the enamel, visible even on a wet tooth. Still no hole.
- Stage 3: Localized breakdown of the enamel surface. A small chip or pit has formed, but the deeper dentin layer isn’t visibly involved yet.
- Stage 4: A dark shadow from the dentin shows through the enamel. The decay has spread beneath the surface.
- Stage 5: A distinct cavity with dentin visibly exposed inside the hole.
- Stage 6: An extensive cavity. A large portion of the tooth structure is lost, with dentin clearly visible across a wide area.
Stages 1 and 2 can often be managed without drilling through fluoride treatments and improved hygiene. By stage 3 and beyond, the tooth typically needs a filling or more involved restoration. The earlier you catch it, the simpler and less invasive the fix.