Dental Caries / Tooth Decay / Dental Cavity

Dental caries is the scientific term for tooth decay or dental cavity.

Q: How does it occur?

Certain bacteria in the mouth (eg Streptococcus mutans) converts sugar into acid which consequently destroys tooth structure starting from the enamel and then into dentine.

Q: Does it mean that if I consume sugary drinks or food I will definitely get a cavity?

No. Our teeth undergo a dynamic process of destruction/demineralisation (caused by the acid attack) and repair/demineralisation (assisted by buffer from our saliva and fluoride from toothpaste). A tooth cavity forms only when destruction occurs more rapidly than repair.

Q: What accelerates tooth decay?

  • Frequent consumption of sugary food and drinks.
  • Excessive amount of sugary food and drinks.
  • Poor oral hygiene – poor toothbrushing technique and irregular flossing
  • Morphology of the tooth – certain features of our teeth trap food and plaque easier

Q: Is tooth decay reversible? Can a tooth heal itself?

Yes. Only if the cavity is confined to the outer layer of the tooth aka the enamel. Once a cavity encroaches into dentine, the process is irreversible.

Q: What are the symptoms of tooth decay?

It can range from having no symptoms, sensitivity to hot/cold/sweet food, and even a toothache. Most of the time, the larger the cavity, the more severe the symptoms.

Q: What can I do to prevent dental cavity?

Good oral hygiene, moderate consumption of sugary food and drinks, use of fluoride toothpaste, fissure sealants & regular visits to the dentist. Most dentists also take XRays (Bitewing radiographs) to look for early signs of dental cavity.

Q: If I have a dental cavity, what should I do?

See a dentist as soon as possible. The longer you wait, the larger the cavity becomes.

Below are some pictures to show how a dental cavity looks like and what dentists do to fix it.

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1. A dental cavity is present on the lower left second molar. There is also an amalgam(metal) filling on the lower left first molar. The patient does not have any symptoms. The patient also wishes to change her amalgam filling to a tooth coloured filling for aesthetic reasons. Changing amalgam fillings for health reasons is a debatable issue.


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2. After giving local anesthesia, a rubber dam (the blue stuff) is placed to control moisture and improve the field of work. The rubber dam also helps control amalgam fillings and mercury vapour from falling into the oral cavity.


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3. The soft demineralised tooth structure are removed together with plaque retentive areas. Note that once removing decay, the cavity always appear larger than what is first seen. We can also see the black spot on the first molar is actually stains caused by the previous amalgam filling.


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4. Tooth coloured fillings (composite) are placed. These days, we try to make them look pretty and functional at the same time.




My dentist says I have a cavity under a white filling. The white filling was done 4 years ago as replacement for an old amalgam filling. How can a cavity develop inside my tooth under the filling? And how can dentist fix the cavity and repair my tooth?

    Dr Mong Xeng Tien

    The cavity can re-occur if the existing filling is leaking, or if there is left over decay prior to placing the filling.
    The dentist can fix it be replacing the existing filling.

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