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Description of the structure of a human tooth

description of the structure of a human tooth

Teeth are not only bone formations for mechanical processing of food, but also they are indicators of health and well-being of a human.

Since ancient times, people have had to eat hard food, which needs to be carefully shredded and processed. In particular, white, straight teeth with pink gums always show that a person’s diet is of a high quality and varied.

Scheme

Human teeth are composed of three elements:

  • The crown. The most upper visible part, which is completely or partially visible above the alveoli after the eruption;
  • The neck. The narrower part located in the gum between the primary crown and root.
  • The root. The lowest part which is in the alveoli. There are nerves and blood vessels weave in a pulp of the root. With the help of the periosteum, roots are firmly fixed in the alveolar hole. Depending on the functions performed by a tooth and anatomical features of a person, the number of roots can vary from 1 to 4 units.

The main substance in the structure of the tooth is the dentin, which makes up a large part of its mass. From the chemical point of view, dentin contains collagen impregnated with various salts, phosphorus, and other minerals.

The crown is covered with enamel from the outside part. Due to the fact that the base of the crown consists of inorganic compounds, it is close in strength to the diamond. Metabolic processes take place only in a thin tissue, tightly enveloping surface of not damaged enamel.

The fixation of a tooth is being made of the “special cement” covering the root. In its structure, the cement is very close to the structure of the bone tissue. The blood flow takes place through the branches of external, carotid artery, tightly intertwined with each other. The outflow of the venous blood is through vessels, directly related to the circulation of the blood in the brain.

Such blood circulation, in turn, carries the danger in the case of the initial localization of infection in the oral cavity, through these vessels, it may get into the dura and to cause a number of serious diseases.

An adult human’s jaw has two arcs, each of which has fourteen to sixteen teeth. Children up to twelve years have a different number of teeth – they only have twenty milk.

An external similarity of structure of the upper and lower jaws does not mean that they are identic, so you should learn about their structure and distinguishing features.

Upper jaw

The central incisor is characterized by a flat shape of beveled cutting edge and by a single root. The front part of the incisor is convex and contains three small lobes.

An appearance of a lateral incisor is identical to the central one. But due to the fact that the central lobe is large and stands out much more, it gets a convex faired shape.

Canine – element inherited by a human from ravenous representatives of the fauna. There is just one volume lobe on the crown of the canine. Due to the groove extending on the inside part, a canine is visually divided into two parts.

Small molars (in dentistry called premolars). In contrast to the front teeth, premolars are characterized by a square shape. Roots are though flattened but already start to bifurcate.

Large molars (molars) – are the largest in the entire row and are directly responsible for grinding food. The first molar has a rectangular shape with four knobs that allow chewing food efficiently. The second molar is somewhat smaller in size, but in terms of functionality and structure of the root is almost of no difference from its predecessor.

The third molar, also called wisdom teeth grow significantly later than others. Sometimes they may not erupt at all, it is not a problem, as it performs no important functions and is more of a rudimentary organ.

the structure of human teeth in the upper jaw

Lower jaw

The name and number of teeth of the upper and lower jaws are the same, but they have differences in the structure and functional features.

The front incisors are significantly smaller than their counterparts above. The outer surface has two edges: sharp and dull. The roots are shallow and do not have large dimensions.

The lower canines do not differ from those placed on top, they only have narrower edges.

Molars and premolars of the lower jaw have a different number of bumps for chewing food, as well as roots and canals in them. In contrast to the upper molars, lower have one root less.

Anatomy of molars and premolars

Molars in dentistry are divided into large – molars and small – premolars. Their structure in humans is very different from the front.

Premolars

Humans have two small molars from the left and the right side. The first premolar’s central chewing surface is long, while the far surface is shorter and larger.

The second premolar retains all the features of the first, but it is massive. The upper premolar is somewhat smaller than its lower counterpart.

Molars

Depending on individual anatomical features, the number of molars in humans can range from eight to twelve. Due to the structural features of the jaw, the molars gradually decrease from the center to the edges.

The crowns of molars are large, with a strong square or triangular surface of the closure. On top, there are located from three to five chewing bumps, allowing the molars to fully carry out their responsibilities – the primary processing of food.

The upper molars are characterized by three roots, two of which are directed towards the cheek, and one – to the tongue. The lower molars have only two roots: the back and the front. In the edge molars, roots sometimes are fused together. Third molars also have a very unpredictable form of the crown, which depends on the structure of the skull and the jaw.

the structure of human teeth photo

Incisors and canines

Front teeth are divided by dentists into incisors and canines.

Incisors

Two teeth arranged above and below the jaw arcs are referred to incisors. The crown has a narrow, flattened shape with a sharp edge, as it is designed for cutting pieces of food that are subsequently chewed by molars and premolars.

Incisors of an upper jaw are considerably larger and heavier, while a lower half is almost two times smaller. The roots are single and flat, especially in incisors, located at the bottom. The upper part of the roots is deflected aside.

Canines

Canines are located directly behind the incisors in the upper and lower jaw arcs. These distinguishing features include the fact that the two cutting edges converge at an angle at one point, forming a recognizable shape. Canines have a long root with grooves in the side part.

Upper canines are bigger and more massive, while the bottom is less clearly expressed. Canines located on the lower jaw are shorter and have smooth cutting edge, narrow longitudinal ridges. Roots are noticeably shorter than the upper; they have pronounced grooves.

Wisdom teeth

Wisdom teeth, or, as they are properly called, third molars may erupt at any age, and not necessarily all of them. But at the same time, even if they have not appeared, remained in its infancy, it is not a deviation from the norm.

Third molars are among the most problematic human teeth. They are located at the end of the jaw on both sides, and there is a total of four. The structure of the third molars is no different from the rest of the structure of molars. But at the same time, it has its own peculiarities:

  • wisdom tooth is the last in the row, and is not located between its neighbors;
  • on the spot of the third molar position, children do not have milk teeth, preparing the ground for its eruption, which makes the process more unpleasant and painful;
  • the roots of the third molars are often fused into one large, which may have an irregular conical shape;
  • a crown is not necessarily cut through completely and has different variants of the form.

Typically, third molars grow in age from eighteen to twenty-five years. But sometimes they can appear much later, or not appear at all. These uncut teeth are called impacted or half-impacted if the crown appeared only partially.

Problems with the growth of wisdom teeth due to evolutionary changes in the skull. In the jaws of the modern human body, they are rudimentary, and often for their normal development there is not enough space.

Milk teeth

tooth structure - the pictureTheir formation begins to take place in the womb at the twelfth week. As a rule, the first to appear in a child are incisors, canines, and just at the very end the molars.

Terms of this process are highly individual and may vary, but in most cases, the formation of milk teeth occlusion begins at the age of seven months and ends in three to four years. By this time, the child must have at twenty milk teeth.

Compared to the permanent teeth, milk teeth have their own features:

  • smaller sizes;
  • fewer masticatory tubercles;
  • roots go to the sides.

Despite this, primary and permanent teeth have the same number of roots.

A row of milk teeth on a jaw consists of ten teeth: four large molars, four incisors, and two canines. At the age of six to seven years, milk teeth start falling out and change to constants.

In the first place, there is a change of a large molar tooth and the final formation of a row ends at twelve to fourteen years, with the exception of the third molars.

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