Enamel: The surface layer of the tooth crown, translucent, milky white calcified tissue, containing 96% inorganic matter, 4% water and organic matter.
Dentin: the main body of the tooth, light yellow and shiny, containing 70% inorganic substances and 30% organic substances. There are nerve endings in the dentin, which are pain receptors.
Cementum: A layer of calcified connective tissue on the surface of the tooth root. It is light yellow in color and contains 55% inorganic substances. Its composition and hardness are similar to those of bone but without the Haval tube. Cementum has new functions.
Dental pulp: The loose connective tissue in the pulp cavity, containing blood vessels, lymphatic vessels, nerves, fibroblasts and odontoblasts, has the ability to form secondary dentin. The dental pulp nerve is an unmyelinated nerve and has no positioning ability. The blood vessels enter and exit from the narrow apical foramen, which can easily cause circulatory disturbance and pulp necrosis.