Teeth can be described as hard organs designed for cutting and grinding food, the most important step in what is known as mechanical digestion. They are also involved in modulating voice and sound emitted through the mouth, so they play an important role in speech.
The teeth are located in the sockets of the maxillary and mandibular bones. The human dentition consists of four types of teeth: incisors, canines, premolars and molars. The incisors primarily have a cutting function, the incisors tear and the premolars and molars grind.
Human beings, like other mammals, are animals. difiodonts, that is, they develop only two generations of teeth throughout their lives. The first generation is known as the temporary, deciduous or deciduous dentition. The second generation, whose development begins in childhood and lasts until about 12 years of age, is known as the definitive or permanent dentition.
From a morphological point of view, three parts can be distinguished in each tooth: root, neck and crown. The root is the part inserted into the mandibular or maxillary bones and which is covered by the gum. The crown is the part visible in the mouth and exposed to the outside. The neck or cervix is the area where the crown and root meet.
Fabric composition and layers
Each tooth is made up of several layers of tissue with different composition, density and hardness. The four most important are tooth enamel, dentin, and root cementum. Teeth are also usually studied in conjunction with the periodontium, the set of accessory structures of the tooth, for example, attachment ligaments.
Dental enamel is a very hard mineralized tissue, so much so that it is the hardest and most mineralized substance in the human body.96% inorganic substances mainly hydroxyapatite a mineral composed of crystalline calcium phosphate (CA5(PO4)3(OH)) 4% water and organic matter without collagen
Enamel appears only on the crown, on the part of the tooth exposed outside the gums, and is supported by the dentin below. Unlike dentin, root cementum, and dental pulp, enamel does not contain collagen, although there is always some small amount of protein, especially during enamel development, such as ameloblastin, amelogenin, enamelin, or tuftelin, which is believed to form the matrix in which minerals are deposited to form enamel.
Enamel color normally ranges from a grayish white to a light yellow with highly variable shades. Enamel is actually translucent, so its color changes depending on the amount of dentin underneath or the presence of other materials, such as materials used for tooth reconstruction. In the part close to the gums, there is almost no dentine under the enamel and it can take on a bluish-white tone.
In the crown, the dentin appears between the enamel and the pulp (or pulp chamber), and in the root it appears between the root cementum and the pulp. Dentin is secreted by odontoblast cells of the tooth specialized in the formation of dentin and enamel.
The approximate composition of dentin is:70% inorganic substances, mainly hydroxyapatite 20% organic substances, especially collagen 10% water
Dentin is on mineralized connective tissue with a matrix of collagen fibers on which hydroxyapatite minerals are deposited. Under the microscope you can see several channels, called dentinal tubules, which radiate from the pulp to the enamel or, in the root, from the pulp to the root cementum.
The diameter of the dentinal tubules varies from approximately 2.5 µm closer to the pulp to 900 nm closer to the enamel. The tubules do not intersect, although they do have some collateral branches.
Dentin is softer than enamel. If the enamel layer is lost, the dentin deteriorates much faster.
Root cementum is a specialized substance that covers the root of the tooth and serves as an anchor site for supporting ligaments.
Its texture is similar to bone tissue and is formed in a 45% of mineral substances, and as the inorganic fraction of dentin and enamel, the main mineral substance is hydroxyapatite. 33% is organic matter, mainly collagen, and 22% is water.
Root cementum is formed by cementoblasts, present only in the lower third of the root of the tooth. The upper two-thirds of the root cementum is acellular.
The dental pulp is the central part of the tooth. It is sometimes called the pulp chamber and is composed of connective tissue filled with blood vessels and nerve fibers that enter through the tips of the roots.
The junction between pulp and dentin is lined by odontoblasts and cementoblasts, which form dentin and root cement, respectively. In the pulp can also be seen fibroblasts and various immune cells, especially macrophages and T cells.