Tooth enamel: the hard armor of teeth

Teeth are one of the hardest organs in the human body. They not only bear the important function of chewing food, but also participate in pronunciation, maintain facial beauty and many other functions. Understanding the structure and function of teeth will help us better protect the health of teeth.

Tooth enamel is the outermost layer of hard tissue of teeth, mainly composed of hydroxyapatite crystals and a small amount of organic matter. It is the hardest substance in the human body. Its hardness is about 5 times that of bones, and it has a high degree of mineralization and corrosion resistance. The main function of tooth enamel is to protect the pulp and dentin from external stimuli, and it also helps chewing and pronunciation.

The formation of tooth enamel begins in the embryonic period and continues to mineralize and thicken after birth. This process requires the participation of minerals such as calcium and phosphorus and vitamin D, as well as the normal differentiation and function of ameloblasts. If the formation process of tooth enamel is disturbed, it may cause enamel hypoplasia or deformity.

Tooth enamel diseases mainly include caries, enamel hypoplasia and incomplete enamel calcification. Tooth decay is caused by bacteria using food residues to produce acid, which leads to the demineralization of tooth enamel. In order to protect tooth enamel, we should pay attention to oral hygiene and avoid consuming too much acidic food and beverages. If tooth enamel is damaged, it can be repaired by filling, veneer, porcelain crown and other methods.

Dentin: the main structure of teeth

Dentin is the main component of teeth. It is located in the inner layer of enamel and cementum. It is light yellow in color and contains about 30% organic matter and water and 70% inorganic matter. The hardness of dentin is lower than that of enamel, but it is still an important hard tissue of teeth.

Observed under a microscope, there are many regularly arranged thin tubes in dentin, called dentinal tubules, and there are nerve fibers in the tubes. When dentin is exposed, it can sense external stimuli such as cold, hot, sour, and sweet, causing pain. Therefore, dentin plays a vital role in protecting the pulp.

The formation of dentin runs through a person's life and can be divided into primary, secondary and tertiary dentin. Primary dentin is formed during tooth development, secondary dentin is formed slowly after tooth eruption, and tertiary dentin is formed when teeth are stimulated by wear, trauma or caries.

Cementum: Protective layer of tooth root

Cementum is a layer of bone-like tissue covering the surface of the tooth root, which protects and supports the tooth and keeps it fixed in the alveolar socket. The hardness of cementum is similar to that of bone tissue, but lower than that of enamel and dentin. Its structure is lamellar and is divided into two types: acellular cementum and cellular cementum.

Acellular cementum has only calcified intercellular matrix but no cells, and is often evenly distributed on the surface of the entire root dentin. There are many pits in the interstitium of cellular cementum, which contain cementum cells. These cells can continuously form new cementum and repair the damage of the root surface.

Cementum has two important functions: one is to combine periodontal tissue and tooth tissue together, and the other is to repair the damage of the root surface. This repair ability is of great clinical significance, especially when the teeth are damaged by excessive bite force or other factors.