Tooth and jaw structure

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Tooth and jaw structureThere are 3 parts in a tooth: crown, neck and root.

A crown is the part of the tooth that protrudes into the oral cavity; neck - the place of transition of the crown to the root; root - a part of the tooth, immersed in the alveolus - (cell) of the jaw.

The human tooth consists of soft and hard tissues. The soft tissue is the pulp that fills the tooth cavity. Hard tissues include enamel, dentin, and cementum.

Enamel covers the crown of the tooth. It is the densest tissue in the entire human body. The solid base of the tooth is denin - a tissue somewhat inferior in density to enamel, but still denser than cement. Dentin is penetrated by many tiny tubules through which this tissue communicates with the cavity of the tooth and with the pulp in it. The part of the tooth, which is hidden in the jaw, is covered from the neck to the apex of the root with cement - a substance that is rather hard, but less dense than enamel and dentin: in its structure, the cement is extremely close to bone tissue. The pulp is a delicate tissue with many vessels and nerves. The neurovascular bundle enters the pulp through a hole in the root apex. In addition to blood vessels, there are also lymphatic vessels in the pulp tissue.

Between the root of the tooth and the cell of the jaw (alveolus) there is a slit-like space made by soft tissue and called the periodontium. Periodontal tissue consists mainly of connective tissue fibers extending from the cement to the alveolar wall. The tooth is suspended on these fibers. In addition to connective tissue, there are a large number of blood vessels and nerves. The tooth and the periodontium are closely related, representing a single whole. As part of the body, teeth have an impact on it. The vital activity of the body also, in turn, affects the occurrence of certain pathological processes in the tooth and the periodontal tissues. Thus, in no case should you look at a tooth as something separate.

The upper jaw ranks first among the bones of the facial skeleton. Despite its size, it is very light, since it contains an extensive cavity called the maxillary (maxillary) sinus. The walls of the jaw surrounding the maxillary sinus are thin; the sinus communicates with the nasal cavity through a small opening. From the body of the jaw, the alveolar processes are directed downward, in which the teeth are strengthened. The upper jaw is in close proximity to the orbit, and around the upper jaw there are tissues with a large number of nerves and veins that emerge from the cranial cavity. There are also many arteries, some of which are directed through the bony openings to the brain.

If the upper jaw is a light bone with relatively thin walls, then the lower jaw in this respect differs significantly from it. The bone of the lower jaw is dense; there are no cavities in it, there is only a narrow channel through which the neurovascular bundle passes.

Tooth and jaw structureThe motor and sensory nerves of the jaws are branches of the trigeminal nerve.

The alveolar processes are covered with a mucous membrane, which passes from the jaws to the oral cavity. The mucous membrane in the area of ​​the jaw bones is closely adhered to the periosteum and, thus, to the bone itself. In the area of ​​the floor of the oral cavity and in the transition from the upper to the lower jaw, the mucous membrane sometimes forms a rather large number of folds.

There are a large number of lymph nodes in the soft tissues surrounding the jaw and oral cavity; especially there are a lot of them in the submandibular region.

The teeth are nourished through the pulp and periodontium. It is assumed that the pulp nourishes the enamel and dentin, and the periodontium nourishes the cement and partly the dentin.

In the tissues of the tooth, organic and inorganic components are distinguished. Of the inorganic substances, the composition of the tooth includes mainly calcium salts, mainly calcium phosphate, in second place after calcium is magnesia phosphate. There are few organic substances in the hard tissues of the tooth, especially few in the enamel - only 3.5%. Dentin contains much more organic matter than enamel; cement, as already mentioned, in its chemical composition, as well as in structure, is close to bone.

Due to the presence of a large number of nerves in the periodontium and tooth pulp, these tissues are extremely sensitive to pain. Of the hard tissues, only dentin is painful, and the degree of sensitivity for each person is different. There are people with hypersensitivity who experience great suffering even with minor dental procedures. In such cases, it is customary to speak of "sensitive dentin".

Of the physical properties of a tooth, its ability to withstand very strong pressures deserves special attention. This is evidenced by at least the following example: a gymnast holds in his teeth a metal plate with a trapezoid, on which another gymnast does exercises.

The oral cavity as a whole, as you know, takes part in one of the most important physiological acts - the act of digestion. The teeth perform a mechanical function here: through the movement of the lower jaw, they grind and grind food. Food in the mouth is also chemically processed.

The upper and lower jaws must be in a certain position in relation to each other (correct bite); in this case, the act of chewing will be most successful. The correct bite (articulation) is such a position of the jaws in which the teeth of the upper jaw slightly protrude behind the teeth of the lower jaw, and the cheek tubercles of the chewing surfaces of the small molars and large molars lie in the groove of the lower ones. The chewing function is quite complex; it consists of a number of combined movements, the main ones of which are: 1) opening and closing the mouth, 2) movement to the sides and 3) movement forward and backward.

Yu. B. Gorsky - Take care of your teeth


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