A cavity, known scientifically as dental caries, is a hole that forms in a tooth due to gradual decay. It develops when the hard outer layers of a tooth are progressively broken down, creating an opening or pit.
Oral Bacteria and Sugar
The human mouth naturally hosts diverse bacteria, some directly involved in tooth decay. Species such as Streptococcus mutans and Lactobacillus strains are implicated in cavity formation. These bacteria thrive on the sugars and other fermentable carbohydrates in daily diets. When these bacteria encounter sugars, they metabolize them through fermentation. This activity produces various acids, primarily lactic acid. The presence of these acid-producing bacteria and their food source creates an environment conducive to initial tooth damage.
The Formation of Plaque and Acid
A sticky, colorless film called plaque constantly forms on teeth. This film, composed of oral bacteria, food particles, and salivary components, adheres firmly to tooth enamel, providing a protected environment for bacteria. Within this plaque, bacterial acids become trapped against the tooth surface. This localized acid concentration prevents saliva from effectively neutralizing acidity or washing away harmful byproducts. Plaque acts as a protective barrier, maintaining prolonged contact between acids and enamel.
Enamel Erosion
Tooth enamel is the outermost layer of a tooth and the hardest substance in the human body. It primarily consists of mineral crystals like hydroxyapatite, which contain calcium and phosphate. When the acids trapped within plaque come into contact with enamel, they begin to dissolve these protective minerals. This process, known as demineralization, involves the leaching of calcium and phosphate ions from the enamel structure. Initially, this damage may appear as a dull white spot on the tooth surface, indicating mineral loss. If detected early, and with appropriate changes, this initial stage of enamel demineralization can sometimes be reversed.
Deeper Damage
If the acidic attack on enamel continues without intervention, demineralization progresses beyond natural repair. Eventually, the enamel’s structural integrity is compromised, leading to a cavity. Once decay breaches enamel, it then reaches the underlying dentin layer. Dentin is softer and more porous than enamel, making it more susceptible to acid attacks and rapid decay progression. If decay advances through dentin, it eventually reaches the pulp, the innermost part of the tooth, leading to discomfort and infection.
Influencing Factors
Several factors influence cavity development and progression. Saliva plays a significant role in protecting teeth. It helps neutralize acids produced by bacteria and contains minerals that can aid in the remineralization of early enamel lesions. Dietary habits also contribute, particularly the frequency of sugar and carbohydrate intake. Frequent snacking provides a constant food source for acid-producing bacteria, increasing acid exposure to tooth surfaces. Tooth anatomy, such as deep grooves and pits on the chewing surfaces of molars, can create areas where food particles and plaque are trapped. Insufficient oral hygiene practices, which allow plaque to accumulate unchecked, prolong the contact between acids and tooth enamel.