🦷 TOOTH DECAY & PULP

Dental Caries (Cavities)

Korean: 충치 · 한국어 설명 보기

Also called: cavity · tooth decay · caries

In short

Cavities are holes created by acid from bacteria feeding on sugar. Decay confined to enamel can sometimes be arrested without drilling; once it reaches dentin, the tooth structure is gone permanently and must be filled. Pain appears late — usually only after the decay is already deep.

The actual mechanism

Bacteria in plaque metabolise sugars and starches and release acid as a by-product. That acid dissolves mineral out of the tooth surface — a process called demineralisation. Saliva pushes minerals back in between meals. A cavity forms when the acid attacks outpace the repair.

This framing matters because it explains something counterintuitive: how often you eat sugar affects decay risk more than how much. One dessert produces one acid episode. Sipping a sweetened coffee across three hours produces a near-continuous one, and saliva never gets a window to repair.

How far it has gone — and what that means for you

StageWhat is happeningSymptomsTreatment
Initial (white spot)Mineral loss in enamel, surface intactNonePossibly reversible — fluoride, plaque control
Enamel cariesSurface has broken; no dentin involvementUsually noneSmall filling
Dentin cariesInto dentin; progresses faster hereSensitivity to cold, sweetFilling or inlay
Deep / near pulpApproaching the pulpLingering pain, throbbingDeep restoration or root canal
Pulp involvementBacteria reach the nerve — pulpitisSevere or spontaneous painRoot canal, then crown
Where the line is: enamel has no nerves and no cells, so early enamel lesions can sometimes remineralise. Dentin cannot rebuild itself. Once decay crosses into dentin, that structure is permanently lost — the only question is how much gets replaced with filling material.

Why "it doesn't hurt" means very little

Enamel contains no nerve supply at all. Pain begins only when decay reaches dentin, and reliable pain usually means it is deep. So the entire early, cheap, easily-treated phase of a cavity is silent by design.

This is also why interproximal decay — between the teeth — is so commonly missed. It is invisible in a mirror and painless for months, and it is found on a bitewing radiograph. If you have not had films taken in several years, undetected decay between teeth is the most likely thing hiding.

The sites that account for most cavities

  • Molar grooves and pits — narrower than a single bristle, so a brush cannot enter them.
  • Between teeth, just below the contact point. Requires floss; brushing does not reach.
  • At the gumline, especially where gums have receded and softer root surface is exposed.
  • Around the edges of old fillings and crowns — a gap of a few tenths of a millimetre is enough.
  • Around orthodontic brackets.
  • Partially erupted wisdom teeth, and the back surface of the molar in front of them.

Prevention that actually changes outcomes

  • Fluoride toothpaste, and do not rinse with water afterwards. Spit, don't rinse — rinsing washes away the fluoride you just applied. This single habit change has a measurable effect.
  • Reduce the frequency of sugar exposure, not just the quantity. Confine sweets to mealtimes rather than grazing.
  • Clean between the teeth daily. This is where the decay you cannot see happens.
  • Fissure sealants for deep molar grooves, especially in children.
  • Bitewing radiographs at intervals appropriate to your risk — this is how interproximal decay gets caught while it is still small.
A note on "natural" remedies: oil pulling, charcoal, and dietary supplements do not close a cavity that has broken the enamel surface. Early white-spot lesions can remineralise with fluoride and plaque control. A hole cannot. Delaying a small filling reliably produces a larger one, and often a root canal.

What treatment involves

Decayed tissue is removed and the space is restored — with composite resin for smaller cavities, or an inlay/onlay when a large portion of the tooth is gone. If decay has reached the pulp, root canal treatment becomes necessary and the tooth generally needs a crown afterwards, because a treated tooth with a large cavity is structurally weakened and prone to fracture.

Current fees for fillings, inlays, and root canal treatment are published on our English price list.

Frequently asked questions

Can a cavity heal on its own?

Only at the very earliest stage. A white-spot lesion — mineral loss with the enamel surface still intact — can remineralise with fluoride and improved plaque control. Once the surface has broken and especially once decay reaches dentin, the lost structure cannot regenerate and a filling is required. There is no product or diet that closes an actual hole.

My tooth has a hole but does not hurt. Can I wait?

Waiting reliably makes it more expensive. Enamel has no nerves, so absence of pain tells you very little about depth — pain typically begins only when decay is already close to the pulp. A small filling today is a substantially smaller procedure than the root canal and crown the same tooth may need in a year.

Why do I get cavities when I brush twice a day?

Because the sites where cavities form are the ones a brush cannot reach: between teeth, deep molar grooves, and the margins of old fillings. Brushing handles the flat visible surfaces well. If you are getting decay despite good brushing, the two things to add are daily interdental cleaning and periodic bitewing radiographs to catch what is invisible.

Does sugar quantity or frequency matter more?

Frequency. Each sugar exposure triggers an acid episode lasting roughly 20 to 40 minutes, and saliva needs the gaps in between to remineralise. One dessert with a meal is one episode; sipping a sweet drink over three hours is a nearly continuous attack. The same total sugar can be low-risk or high-risk depending purely on timing.

Are dental X-rays really necessary to find cavities?

For decay between teeth, yes — it is not visible on examination and produces no symptoms until it is deep. Bitewing radiographs are the standard way to detect it early, when a small filling is still sufficient. If you have gone several years without films, interproximal decay is the most common thing found when they are finally taken.

What is the "spit, do not rinse" rule?

After brushing with fluoride toothpaste, spit out the excess but do not rinse with water. Rinsing immediately washes away the fluoride that would otherwise keep working on your enamel surface. It is one of the few no-cost habit changes with a measurable effect on decay rates, and most patients have never been told it.

Related terms

Tooth EnamelDentinDental PulpPulpitisWisdom ToothTooth Fracture

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