Tooth decay

Tooth decay, also known as dental caries, is the breakdown of tooth structures. The word "caries" comes from the Latin word for "rottenness."

This condition occurs when acids dissolve the hard tissues of the teeth. These tissues include the enamel, the dentin, and the cementum. Decay can cause many different colors, ranging from yellow to black. Symptoms often include physical pain and difficulty eating. If left untreated, complications can include inflammation of surrounding tissue, tooth loss, or the formation of an abscess.

The mechanism of decay involves a complex interaction between bacteria, food, and the tooth surface. Bacteria in the mouth form a sticky, creamy mass called plaque. This plaque acts as a biofilm, which is a sheltered environment for microbes.

Certain bacteria, such as Streptococcus mutans and Lactobacillus, are highly cariogenic, meaning they cause decay. These bacteria consume fermentable carbohydrates like glucose, fructose, and sucrose. Through a process called fermentation, they convert these sugars into acids, primarily lactic acid.

These acids cause demineralization, which is the dissolution of the tooth's mineral content. If the rate of mineral loss is greater than the buildup from saliva, a cavity forms.

Decay progresses through several distinct stages and visual changes. The earliest sign is often a chalky white spot on the enamel. This is called an incipient carious lesion or a "micro-cavity." As demineralization continues, the spot may turn brown and eventually progress into a cavitation, or a physical hole.

If a lesion appears dark brown and shiny, it may mean the demineralization has stopped, leaving only a stain. Active decay, however, usually appears lighter in color and looks dull. As the decay moves through the enamel into the dentin, the tooth may become sensitive to heat, cold, or sweets. This happens because the dentinal tubules, which lead to the tooth nerve, become exposed.

Several factors influence how quickly decay develops. The frequency of acid exposure is a major driver. After eating sugar, the pH level in the mouth drops suddenly.

This drop is shown on the Stephan curve, which tracks how acidity changes after sugar consumption. While saliva helps buffer this acid and return the pH to normal, frequent snacking keeps the teeth in an acidic state. Other risk factors include low saliva production. Conditions like diabetes mellitus or Sjögren syndrome can reduce saliva. Some medications, such as antidepressants or antihistamines, also decrease saliva. Furthermore, receding gums can expose the roots, which are more easily decayed because of the cementum.

Historically and socially, dental caries show significant global patterns. The disease is more common in the developed world due to higher consumption of simple sugars. However, access to professional dental care is often much lower in the developing world. Socioeconomic status also plays a role, as poverty can limit education about dental care and the ability to pay for treatment. Interestingly, dental decay can be passed from a caretaker to a child. This happens through a caretaker's kiss or by feeding a child pre-masticated food, which spreads certain bacteria.

The scale of this issue is massive. As of 2016, approximately 3.6 billion people, or 48% of the global population, had caries in their permanent teeth. In baby teeth, the condition affects about 620 million people, which is 9% of the population. The World Health Organization estimates that nearly all adults will experience dental caries at some point in their lives. Because the disease is becoming more common in both children and adults, prevention is a global priority. Currently, scientists are researching stem cell-based methods to see if tooth regeneration is possible. For now, medical science focuses on easing symptoms and restoring function.

Prevention and treatment are the primary ways to manage the disease. Regular cleaning and a low-sugar diet are essential. Brushing twice a day and flossing once a day are highly recommended.

Fluoride is a vital tool for prevention. It can be found in water, salt, or toothpaste, and it aids in the remineralization of the tooth.

If a cavity has already formed, a dentist may use various treatments to restore the tooth. This might include fillings to close the hole.

In very advanced cases where the pulp tissue is overwhelmed or the tooth is too weak, the tooth may need to be removed entirely.