Tooth decay: main concepts and causes

Main causes

Three groups of factors will have to act for dental caries to form. These factors are also known as cariogenic factors.

1. Infective factor

   The mouth contains a wide variety of oral bacteria, but only a few specific species of bacteria are believed to cause dental caries : Streptococcus mutans and Lactobacilli are among them.

   Bacteria collect around the teeth and gums and more likely in sites that provide microscopic retentions for dental plaqueDental plaque is a sticky, pale-yellow film of bacteria that forms on teeth. :

   • The grooves on the occlusal surfaces of molars and premolars

   • The areas between teeth also called interproximal sites

   
   

   

   tooth decay inside the grooves on the occlusal surface of a molar

   

   decay in the interproximal site between two teeth

   
   

2. Food factor

   The food factor is represented by the fermentable carbohydrates such as sucrose or table sugar. Bacteria from the mouth convert these carbohydrates into acids (such as lactic acid) through a process called fermentation.

   If left in contact with the tooth, these acids may cause demineralization, which is the dissolution of its mineral content. If demineralization continues over time, enough mineral content may be lost so that the soft organic material left behind disintegrates, forming a cavity or hole.

   Moreover, dental plaque develops particularly when foods containing carbohydrates are frequently left on the teeth.

   Basically, bacteria that live in the mouth thrive on these carbohydrates, producing acids that will progressively destroy tooth enamel and dentin, resulting in tooth decay.

   
   

3. Tooth structure

   Tooth structure refers to the quality and hardness of dental tissues. There are certain diseases and disorders affecting teeth that may leave an individual at a greater risk for cavities.

   In these cases, teeth may be left more vulnerable to decay because the enamel is not able to protect the tooth.

   Although tooth structure is not the primary cause of dental caries, it is still an important factor.

   Dentin and cementum are more susceptible to caries than enamel because they have lower mineral content. Thus, when root surfaces of teeth are exposed from gingival recession or periodontal disease, caries can develop more readily.

   Moreover, the particular anatomy of each tooth may affect the likelihood of caries formation. Where the deep developmental grooves of teeth are more numerous and exaggerated, pit and fissure caries are more likely to develop. In addition, caries are more likely to develop when food is trapped between teeth.

Other risk factors

Reduced salivary flow rate is associated with increased caries since the buffering capability of saliva is not present to counterbalance the acidic environment created by acid fermentation.

As a result, medical conditions that reduce the amount of saliva produced by salivary glands (for example, Sjogren's syndrome, diabetes mellitus and others), medications, such as antihistamines and antidepressants, that can also impair salivary flow, or radiation therapy of the head and neck, may also increase the likelihood of dental decays.

Other risk factors may include the use of tobacco, intrauterine and neonatal lead exposure, extreme poverty etc.