1. Chemical bacterial theory (original theory of acid, chemical parasitic theory) Bacteria → sugar and carbohydrates in food, acid production → dental demineralization → organic matter damage → caries

2. Protein lysis theory Bacteria produce protein lytic enzymes → destruction of organic matrix in enamel → dissolution of mineral salts → caries disease

3. Protein lysis—Chemistry theory Bacteria → Protein lysis enzymes destroy organic components in teeth, and their products combine with dental minerals through chelation → Solubility Chelating → Teeth destruction

1. Bacteria

2. Bacterial plaque (key point):

<Principle of caries in plaque> Bacteria in plaque use sugar to produce acid. The pH value of bacteria metabolized acid production is lower than 5.5, crystal dissolution----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Demineralization is greater than remineralization, causing caries

Ingredients of food: Sucrose is more likely to cause caries; Properties of food: Sticky foods are prone to caries, and are rich in fiber and not prone to caries; Lack of VitD, A, B, and the incidence of caries is high; Deficiency of calcium and phosphorus, and the incidence of caries is high; Malnutrition is prone to caries and proteins; Poor health throughout the body can easily cause caries. Fluoride ions promote remineralization and can resist caries

teeth: (1) Different parts: (2) The structure of the teeth: (3) The development status of enamel and mineralization status

saliva: The function of saliva: 1 It can wash away the sugar that adheres to the teeth; 2. It can buffer the acid produced in plaque; 3. Contains IgA and lysozyme have antibacterial and anti-carious effects. Quantity: The secretion volume decreases and caries are affected in a short period of time; Quality: Increased viscosity can easily cause caries.

(1) Form: It is also triangular, with a smooth surface, but the base is facing the enamel dentin boundary and the top is facing the wall of the gutter. (2) Formation: First, two small flat caries are formed on the two walls of the pit and groove in an annular shape, extending to the deep part, and then expanding, and then converge at the bottom of the pit and groove into a cone (bottom is at the enamel boundary); (3) Hazard Finally, potential caries with small mouth and large bottom are formed. Not easy to detect, there are no obvious large cavities, but the inner surface is damaged more (4) Progress: The bottom of the pits and grooves is thin. The bottom of the pits and grooves is wide. The lesions can easily progress to dentin. The pits and grooves and grooves are progressive quickly and have a serious degree.

Because the lumen of the dentin tube becomes narrower and mineral salts are deposited in the lumen, free inorganic salt ions in the surface demineralization layer are deposited in and around the protrusions of the dentinocytes. The lumen of the dentin tube becomes narrower. Crystal deposition gradually increases Completely blocked tubular The refractive index in the lumen is similar to that in the surrounding interstitial mass Transparent Because of its remineralization, it is also called a hardened layer. However, microhardness analysis shows that the hardness of this layer is lower than that of normal dentin, and there is inorganic salt dissolution between and around the tubes, and demineralization to a certain extent. It's just that remineralization is greater than demineralization

Features There is basically no bacterial invasion in the tube, just the diffusion of acid. There is demineralization and remineralization of dentin peritus and inter-tube dentin, but the former is greater than the latter. The morphology of dentin tubules is still relatively complete, and the collagen fibers are basically intact. The formation of a deep transparent layer blocks the source of nutrients of the tubules. The distal part of the dentin cells protrude and denaturate, and the tubules are empty and filled with air. The dentin grinding sheet is observed under transmitted light. This area is dark black and opaque, which is called a dead zone. Since the demineralization layer has been demineralized, it is checked that this layer has been softened, and these softened dentins do not need to be removed during clinical cave preparation.

Features: The wall of the tubules softens due to demineralization and protein dissolution. The local tubules swell and deform the wall of the tubes due to bacterial reproduction, and blue appears under the light microscope. As demineralization worsens and organic matrix decomposition, the tubules fuse to each other to form liquefied necrotic foci, which is filled with bacteria and necrotic matrix residues. The broken foci can be parallel to the direction of the small tube, sometimes making the small tube beaded, or it can form transverse cracks perpendicular to the small tube.

Under the light microscope, the pulp dentin is a physiological complex. When dentin caries occur, pathological stimulation can be transmitted to the pulp tissue through dentin tubules and dentinoblast cell protrusions, resulting in different reactions in the pulp tissue.