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Our teeth are used for grinding food, but they are also decorations, of course only when they are he althy. Natural teeth are yellow-white, bluish-white is found in asthenic people. What else do you need to know about your teeth? How is a tooth built?
Most of us associate the word " tooth " with a schematic drawing from school textbooks, showingtooth cross-sectionconsisting of three pulp layers , enamel and dentin. In factthe structure of the toothis a bit more complicated. What tissues does the tooth consist of? What is the difference between the anatomical structure and the histological structure of teeth?
Tooth anatomy
Generally speaking, each tooth consists of a crown visible in the mouth and a root located under the gum surface. The intermediate part between the crown and the root is the tooth neck. Roots are structures embedded in the bone and are responsible for keeping the tooth in the correct position. We distinguish one-, two- and three-rooted teeth (sometimes there are more roots). The tooth roots come in all shapes and sizes. They can be straight or bent, they can be separate structures or blending together. Similarly, tooth crowns come in a variety of shapes and sizes. Each of us has slightly different teeth, but some features remain constant, making it possible to recognize whether the tooth we see is an incisor or a molar. The tooth is not a uniform, hard structure, there is a free space inside, the so-called chamber and root canals filled with living tissue - pulp.
It is worth reminding here that a child's full milk dentition consists of 20 teeth. The deciduous teeth fall out with age, and their steadfast successors take their place. An adult set of dentition consists of 8 incisors, 4 canines, 8 premolars and 12 molars (including wisdom teeth). A total of 28-32 teeth.
Histological structure of the tooth, i.e. what tissues the tooth consists of
Each tooth, whether it is milky or solid histologically, consists of the same tissues. There are four main components that make up the tooth: enamel, dentin, cementum and pulp. The first three tissues are highly mineralized and consist mainly of inorganic compounds, hence their other name - hard tooth tissues. The pulp is the only living tissue, numerous vessels and nerves run through it.
Tooth enamel
Enamel (Latinenamelum ) is the most superficial layer that protects the tooth. It starts around the tooth's neck and covers the entire crown. The thickness of the enamel layer is approximately 1-2 mm. It is composed of approximately 96-99% inorganic substances, the remainder being organic compounds and water. Inorganic compounds in the form of hydroxy- and fluoroapatites are tightly packed in a regular crystal structure. Thanks to its structure, the enamel is characterized by exceptionally high hardness. The hardness of the enamel is comparable to that of topaz, a mineral used in jewelery.
Enamel during tooth development, i.e. odontogenesis is produced by specialized cells called ameloblasts. The crystals are deposited in layers until the full thickness of the glaze is formed. Unfortunately, during the process of tooth eruption, the ameloblast layer disappears and we are deprived of the natural possibility of adding new enamel layers.
Dentin
Dentine forms a layer of the tooth that lies beneath the enamel (or cement in the case of tooth roots) and outside the pulp. It is a component of both the crown and the roots of the teeth. Its thickness is a few millimeters. About 20% of dentin consists of organic substances, mainly in the form of collagen and silver-absorbing fibers, which are surrounded by mineral compounds (dihydroxyapatite) - 70%. It is the mineral substances that are responsible for the hardness of this tissue. When looking at dentin under a microscope, you can see that it is not a uniform block of hard tissue. It is crossed by numerous tiny tubules called dentinal tubules. These structures run through the dentin from the pulp towards the enamel, only some of them reach the enamel-dentin junction, the other part ends in the dentin. A single dentinal tubule is filled with an odontoblast appendage (this is the pulp cell responsible for the production of dentin), nerve fiber and tubular fluid. As mentioned, dentin-producing cells, as opposed to enamel-producing cells, are not only present at the stage of tooth formation. Dentine is the tissue that odontoblasts produce almost all their life (as long as the tooth is a living tooth with he althy pulp). Moreover, there are several types of dentin:
- primary dentin is the tissue produced during tooth development; It was assumed that the final moment of primary dentin deposition is the final formation of the tooth root apex
- secondary dentin is produced after the end of tooth development, it is produced throughout life; appearanceresembles primary dentin, but may be less regular
- Tertiary dentin is a tissue produced in response to pathological stimuli; may take the form of reactive or repair dentin
Tooth pulp
Pulp (Latinpulp dentis ) is the only living tissue of the tooth. Shielded by enamel and dentin, it occupies the interior of the chamber and root canals. It connects to the periodontium through the apical opening. During development, pulp is formed from the same tissues as dentin, so that both tissues (pulp and dentin) are closely related. This complex is called the endodontium. The pulp of the tooth is a mature connective tissue that resembles the connective tissue found in the umbilical cord. The only living part of a tooth consists of a base substance in which cells and fibers are immersed. In the microscopic image, three concentrically arranged pulp zones can be distinguished. The innermost layer is the rich cell layer, it is covered by the poor cell layer (called the Weil zone). The most circumferential layer is the odontoblasts (cells that produce dentin). It is adjacent to the youngest part of the dentine, the so-called presentin.
As mentioned, the pulp is the only living tissue of the tooth. It is richly vascularized and innervated, which enables it to perform specific tasks. The basic functions of the pulp include:
- sensory function, thanks to its rich innervation, the pulp registers pain stimuli and enables the body's defensive response
- the nutritional function is to provide nutrients and oxygen needed for the proper functioning of the tooth's tissues
- defense function - in response to pathological stimuli, odontoblasts begin to produce additional layers of dentin (at the site of the pathological stimulus, e.g. a carious lesion), which enables the pulp to be isolated from the oral cavity environment rich in bacteria
Cement
Root cement, otherwise known as ossification, due to its function, is classified as periodontal tissue, i.e. the tissues that hold the tooth in the socket. It covers the surface of the tooth root with a thin layer, its outer layers adjacent to the periodontium. Collagen fibers forming the periodontal ligament penetrate into the root cement, stabilizing the tooth in the socket. Like enamel or dentin, it consists of inorganic and organic substances. With the advantage of the former, therefore it is classified as a hard tissue. Its structure resembles bone, hence its second name - osseous. Due to the content of cells, we can distinguish between two types of cellular cement and acellular cement.