etiology of dental caries, what are the causes of dental caries
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The main causes of dental caries are bacteria, food, saliva, teeth and time
Etiology of dental caries
At present, the recognized etiology theory of caries is the quadruple factor theory, Mainly including bacteria, oral environment, host and time, Its basic points are: Caries-causing foods (especially sucrose and refined carbohydrates) are found in sugar, Tightly attached to the acquired membrane formed by salivary protein on the tooth surface, which is formed by the anatomical structure, biochemical and biophysical characteristics of the tooth surface, not only can be firmly attached to the tooth surface, but also can produce acid in the deep plaque at a suitable temperature and have enough time to erode the teeth, demineralize them, and then destroy organic matter and produce cavities.
It is a necessary condition for caries. It is generally believed that there are two types of cariogenic bacteria, one is acidogenic bacteria, mainly Streptococcus mutans, actinomycetes and Lactobacillus, which can decompose carbohydrates and produce acid, resulting in demineralization of inorganic substances in teeth; The other is gram-positive cocci, which can destroy organic matter and form cavities in teeth after long-term action. At present, it is recognized that Streptococcus mutans is the main cariogenic bacteria, and others include actinomycetes, Lactobacillus and so on.
Bacteria mainly adhere to tooth surface by plaque. After carbohydrates in oral food are degraded, on the one hand, they polymerize to produce high viscosity dextran to form plaque matrix, on the other hand, acid production demineralizes teeth, and the composition of plaque is complex. Besides a large number of bacteria, there are also sugars, proteins, enzymes and other substances.
2. Oral environment
Oral cavity is the external environment of teeth, which is closely related to the occurrence of caries, among which food and saliva play a leading role.
(1) Food is mainly carbohydrate,
It is related to the formation of plaque matrix, It is also the main energy source of bacteria in plaque, Bacteria can metabolize carbohydrates (especially sucrose) to produce acids, and synthesize extracellular polysaccharides and intracellular polysaccharides. The organic acids produced are beneficial to the growth of acid-producing and acid-resistant bacteria, and also to the demineralization of tooth hard tissues. Polysaccharides can promote the adhesion and accumulation of bacteria on tooth surface, and provide energy sources when exogenous sugar is deficient. Therefore, carbohydrate is the material basis of caries.
(2) Salivary fluid under normal conditions,
Saliva has the following functions:
Mechanical cleaning reduces the accumulation of bacteria.
Bacteriostasis directly inhibits bacteria or plaque adhesion on tooth surface.
The anti-acid effect is neutralized by bicarbonate and other substances.
Anti-solubility enhances the acid resistance of teeth and reduces solubility through calcium, phosphorus and fluorine.
When the quantity and quality of salivary fluid change, it can affect the caries rate. Clinically, the caries rate of patients with xerostomia or salivary fluid secretion increases significantly. Patients with maxillofacial radiotherapy may have multiple dental caries due to the destruction of salivary glands; On the other hand, when the amount of lactic acid in saliva increases or the content of bicarbonate decreases, it is also beneficial to the occurrence of caries.
Teeth are the target organs in the process of caries, and the morphology, mineralization degree and tissue structure of teeth are directly related to the occurrence of caries. For example, the pit and fissure of teeth and teeth with poor mineralization are more prone to caries, while teeth with better mineralization degree and proper fluoride content in tissues have stronger caries resistance; On the other hand, the structure of teeth is closely related to the body, especially in the development, which not only affects the development and structure of teeth, but also has great influence on the flow rate, flow rate and composition of saliva, so it is also an important link in the occurrence of caries.
The occurrence of caries has a long process, It usually takes 1.5-2 years from initial caries to clinical cavity formation. Therefore, even if cariogenic bacteria, suitable environment and susceptible host exist at the same time, caries will not occur immediately. Only when the above three factors exist at the same time for a long time can caries occur, so time factor is of great significance in the occurrence of caries.
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