What are the causes of dental caries?

At present, the theory of the etiology of dental caries is a four factor theory, which mainly includes bacteria, oral environment and host (that is, parasites, parasites, viruses and other parasitic organisms) and time. Its basic points are: cariogenic food sugars (especially sucrose and refined carbohydrates) attached tightly to the tooth surface and the acquired membranes formed by salivary proteins. This film not only can be firmly attached to the tooth surface, but also in the appropriate temperature, there is enough time for invasion of teeth in the plaque, the deep acid production, demineralization, and destruction of organic matter, produce caries.
1, bacteria
Is a necessary condition for the occurrence of dental caries, generally there are two kinds of cariogenic bacteria, is a genus of acid producing bacteria, mainly Streptococcus mutans, Actinomyces and Lactobacillus, can make the decomposition of carbohydrates to produce acid, inorganic lead to tooth demineralization; the other is a gram positive cocci, can be broken organic matter, after long-term effect can make the tooth formation of cavity.
2, oral environment
The oral cavity is the external environment of the teeth, which is closely related to the occurrence of dental caries, and the main ones are food and saliva.
(1) food is mainly carbohydrate, which is not only related to the formation of plaque matrix, but also the main energy source of bacteria in plaque. Bacteria can use carbohydrates (sucrose) and acid metabolism, synthesis of extracellular polysaccharide and intracellular polysaccharide, organic acid produced was beneficial to the production of acid and acid resistant bacteria, also conducive to demineralization of dental hard tissue; polysaccharide can promote bacterial adhesion on the surface of teeth and accumulation. And in the lack of exogenous sugar, provide a source of energy.
(2) saliva in normal conditions, saliva has the following functions: first, the role of mechanical cleaning; II antibacterial effect.
When the quantity and quality of saliva changes, the rate of caries can be affected. The incidence of caries in patients with xerostomia or saliva secretion is obviously increased. Patients with maxillofacial radiotherapy may have multiple caries due to the destruction of the salivary glands. On the other hand, when the amount of lactic acid in saliva increases, it also contributes to the occurrence of caries.
3 host
The teeth are the target organs in the process of tooth decay, and the morphology, degree of mineralization and histological structure of teeth are directly related to the occurrence of dental caries.
4, time
The occurrence of dental caries is a long process, from the beginning to the clinical caries formation of cavity usually takes 1.5 to 2 years, even if the cariogenic bacteria, suitable environment and susceptible hosts exist at the same time; dental caries will not happen immediately, only these three factors also exist for a long time, it may produce caries.