What Causes Cavities?

Last Editorial Review: 9/20/2017

Ask the experts

My dentist said I have several cavities. What causes dental cavities?

Doctor's response

Cavity-causing bacteria in the mouth consume simple sugars, converting them into acid plaque. Acid plaque is different from the periodontal plaque that causes "Gum Disease." The acid plaque produced by these bacteria cause the hard inorganic layers of the enamel and dentin to soften. The softened layers are then dissolved by saliva, leaving a hole (cavity) in the tooth. Unless filled by a dentist, the cavity can continue to erode and damage the inner pulp of the tooth. Damage to the pulp can lead to pulp death, infection and tooth abscess. Therefore, pulp damage will necessitate either tooth extraction or a root canal procedure where the dying pulp is removed and replaced with an inert material.

The enamel on baby teeth are immature and porous. It takes seven years for the porous, chalky enamel to be replaced by more mature, dense, hard, shiny enamel. Therefore children are more prone to cavities than adults.

Cavity-causing bacteria are difficult to eradicate because they are very similar to the other harmless bacteria that live in the oral cavity. The many cavity-causing bacteria include:

  1. Lactobacillus acidophilus bacteria reside in the pits and fissures of the chewing (occlusal) surfaces of teeth. These bacteria can cause rampant tooth decay in young children ages 3-12, causing cavities in both baby teeth and the first permanent molars that erupt around age 6.
  2. Six species of streptococcus bacteria attack the smooth surfaces on the sides of the teeth. These sides are usually touching adjacent teeth, and cavities arising on these sides can be difficult to detect visually. These cavities are best detected by the use of x-rays.
  3. Odontomyces viscoses bacteria live on the back of the tongue and attack exposed cementum. Cementum is the hard outer layer of the tooth root (the bottom two thirds of tooth that is normally buried in dental bone). In older patients and in patients with gum disease, the tooth root and cementum become exposed and vulnerable to attack by these bacteria.

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