What Causes Tooth Decay

One of the most common health problems around the world, tooth decay or cavities develop over time to create permanently damaged areas on the tooth enamel.  While most common in adults, children can develop cavities as well.  Developing into tiny holes or openings, cavities are caused by several factors including bacteria in the mouth, frequent eating, sugar intake, and improper teeth cleaning.  This article will address the various causes and risk factors of tooth decay.


Tooth decay and cavity formation occurs gradually over time.  The process of decay development includes:

  • Plaque formation:  A clear film that coats and sticks to the teeth, dental plaque accumulates after eating excessive starches or sugars and not properly cleaning the teeth after.  If the starches and sugar are not cleaned, bacteria begin feeding on them and begin forming plaque on the teeth.  Left on the teeth, the plaque hardens above or below the gum line into tartar.  The hardened tartar creates a shield for the bacteria and makes plaque removal more difficult.
  • Plaque attacks:  The hard, outer layer of the tooth, known as the enamel, begins to erode as acids in the plaque remove minerals.  The erosion creates small holes or openings in the enamel signaling the initial stage of a cavity.  After the enamel is worn away, the bacteria and acid penetrate the next tooth layer (dentin).  Dentin is softer and less resistant to acid than the enamel.  Because dentin contains small tubes which communicate with the tooth’s nerves, sensitivity issues arise once this layer is affected.
  • Damage continues:  As tooth decay progresses through the dentin, acid and bacteria continue penetrating further into the inner tooth layer (pulp).  Containing blood vessels and nerves, the pulp becomes irritated and swollen from the bacteria.  Since there is nowhere inside the tooth for the swelling to expand, the nerves become compressed causing discomfort and pain that can extend to the tooth roots and surrounding bone.

Risk Factors

Anyone with teeth risks developing cavities but the following risk factors can increase the risk:

  • Diet and Nutrition:  Because plaque causing bacteria thrive on sugars and starches, minimizing the intake of these foods/drinks can help reduce the risk of tooth decay.  Additionally, avoiding foods that stick to the teeth, such as candy, honey, milk, and chips, is advisable as these can be difficult to clean leading to decay.
  • Tooth Location:  Because they are harder to reach than the front teeth and have numerous grooves, decay most frequently occurs to the back teeth (premolars and molars) as they are more difficult to clean.
  • Inadequate Oral Hygiene:  If the teeth are not cleaned shortly after eating, plaque can quickly form and begin attacking the tooth enamel.  Flossing should be done at least once per day and brushing should be done twice or after meals.
  • Insufficient Fluoride:  A naturally occurring mineral, fluoride can help stop or potentially reverse the earliest stage of a cavity.  Fluoride is often found in tap water, toothpaste, and mouth washes but can also be professionally applied in a dentist’s office.
  • Frequent Eating:  If sugars are steadily consumed throughout the day, the bacteria in the mouth have constant fuel to produce damaging acids that break down the tooth enamel.

More on Tooth Decay : What are the Stages of Tooth Decay?