Healthy and beautiful teeth are an ornament to any person. Pink gums, even bite and snow-white smile indicate that a person has excellent health and, in general, is considered a sign of his success. Why do teeth get so much attention and because of what happened?
Content
General concepts about teeth and their classification
The teeth are special bone formations that carry out the primary mechanical processing of food. People have long been accustomed to eat a fairly hard food - meat, cereals, fruits of plants. This food needs considerable effort for processing, and therefore healthy teeth are all the time considered to be an indicator that a person eats a variety and well.
For a start, what you need to know about teeth are the only organs in the human body that cannot be restored. And their apparent reliability and fundamentality are rather quickly violated by bad habits and poor care.
And if the milk, primary teeth are fragile precisely because of their temporary purpose, the root ones are given to a person for the rest of their lives. In general, the whole dentition of a person is divided into the following types:
- fangs;
- incisors (lateral and central, they are also called lateral and medial);
- molars or large molars (this also includes the upper and lower wisdom teeth growing in a person at a mature or young age);
- premolars or molars.
As a rule, the location of the dentition in the upper and lower jaws is recorded using the so-called dental formula. For molars and milk teeth, this formula differs only in that the molars are most often denoted with the help of Arabic numerals, and the milky ones - with Latin numerals.
In an adult average person, the dental formula looks like this: 87654321 | 12345678. The numbers denote teeth - each healthy person should have one canine, 2 incisors, 3 molars on each side, 2 premolars on the upper and lower jaws. As a result the total is obtained - 32 pieces.
In babies who have not yet changed their temporary teeth, this formula looks different, since the teeth of everything can be about 20 pieces. As a rule, temporary teeth erupt by 2–3 years, and by 9–12, they are completely replaced by permanent ones. However, not all people will be able to boast of having all 32 germinated teeth.
Since wisdom teeth or third molars can appear in adulthood, they can be completely in their infancy, and in this case, in a person in the oral cavity there will be 28 teeth. Moreover, the structure of the lower and upper jaw has certain differences.
Anatomical structure
The anatomy of a human tooth suggests that it is divided into 3 parts: the root, the neck, and the crown. The crown is the rising part above the gum, it is covered with enamel - the strongest tissue that protects the dental bone from the negative effects of acids and bacteria. There are several types of crown surfaces:
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The facial is the surface on the side of the lip or cheek. - Occlusion is the surface in the area of the closure with the paired tooth, which is located on the opposite jaw.
- Contact - the surface of the crown, which is facing the teeth, located next door.
- Lingual - the inside.It faces the inside of the mouth, that is, the surface that touches the tongue during a conversation.
The neck is the part that is located between the root and the crownconnecting them, covered with cement and covered with the edges of the gums. The root is the part with which the tooth is fixed in its hole. Given the classification of the species, the root is with one or more processes.
Histology
The histological structure of all teeth is exactly the same, but all of them have a different shape, taking into account the specific function performed.
Enamel. it durable fabric, which consists of 95% of various salts, like zinc, magnesium, copper, strontium, fluorine and iron. A 5% are substances such as carbohydrates, lipids, proteins. In addition, the enamel contains a fluid that is involved in physiological processes.
At the same time, enamel also has outer shell, which is called the cuticle, it covers the chewing surface, but over time the cuticle tends to fade and thin.
The basis of tooth bone is dentin is a collection of mineralssurrounding the root canal and the entire dental cavity. The dentin tissue has a large number of the smallest channels, with the help of which the exchange processes take place and also with the help of the channels nerve impulses are transmitted.
Root structure: pulp and periodontium
The cavity inside the tooth forms a pulp - a tissue that is loose and soft in structure, permeated through with nerve endings, as well as lymphatic and blood vessels.
The structure of the roots looks like this. Root is in a special hole - alveolusin the jaw bone tissue. The root, like the crown, consists of a mineral fabric - dentin, covered outside with cement.
Root ends with the topblood vessels that feed the dental bone pass through its opening. The number of roots can vary depending on the functional purpose of the teeth, from 1 root in the incisors, to 5 in the chewing ones.
Periodont is connective tissue, which fills the gap between the hole of the jaw and the tooth root. Fibers of tissue, on the one hand, are woven into the cement of the root, and on the other - into the tissue of the jaw bone, due to which the tooth is firmly fixed. In addition, through the periodontal tissues, the nourishing elements of the blood vessels can get into the dental tissues.
Description of the dentition
Teeth-incisors. The human jaw is arranged symmetrically and includes the same number of teeth of each type. But there are certain anatomical features of the upper and lower jaw. We analyze them in more detail.
Incisors are front teeth.. A person has eight of them - 4 below and above. Cutters are needed to crack the food, divide it into pieces. The special feature of the incisors is that they have a flat bit in the shape of a chisel, with rather sharp edges.
On the anatomical sections there are three tubercles that are erased during life. Jaw on top two central cutters - in its group the largest of all incisors. The lateral incisors are similar in shape with central, but smaller in size.
Remarkably, the cutting edge of the lateral incisor also has three hillocks, and often takes on a convex shape as a result of the development of the central hillock. The root of the cutter takes the shape of a cone, and is flat and single. The distinctive feature of the incisor is from the side of the tooth cavity three tips of the pulpcorresponding to the cutting knob tubercles.
The anatomy of the upper teeth is slightly different from the structure of the lower dentition, thus, everything on the lower jaw is exactly the opposite. Medium incisors smaller unlike the lateral ones, they have a shorter and thinner root than the incisors on the sides. The outer surface of the cutter is slightly convex, while the inner one is concave.
Crown cutter, side arched to the lips and very narrow. The cutting border has 2 corners - in the center, sharper, and inside - more blunt. At the root have longitudinal grooves.
Chewing teeth and fangs
Canines are used to process food into smaller pieces. The anatomy of the canines is such that there is a groove on the inside of the crown, it disproportionately divides the crown into 2 parts. The cutting edge of the canines has one pronounced and developed tubercle; this makes the crown of a cone-shaped form often resemble the canines of a predator.
The canine on the lower jaw is narrower in shape, the ends of the crown are concentrated in the medial tubercle. The canine root is flat, rejected inward and the longest, unlike the roots of other teeth. In man 2 canines on both jaws. Lateral incisors with canines form an arc, where the transition from incisors to chewing teeth begins in the corner.
Consider the structure at the beginning of a small chewing, and after a large chewing tooth. Their main task is careful processing of food. This function is produced by molars and premolars.
Premolars
The first premolar (No. 4 in the dental formula) differs from the incisors and canines in a prismatic shape, on the crown there are convex surfaces. The surface has 2 hillocks - lingual and cheeky, between them are the grooves.
The bump tubercle is much more lingual in size. The root of the first premolar has flat shape, but already with a small split into the lingual and cheek part.
The second premolar is similar in its structure to the first, but its buccal surface is much larger, and the root has a compressed anteroposterior direction and cone-shaped. In the first lower premolar, the chewing surface is inclined toward the tongue.
The second premolar is larger than the first due to the fact that both hillocks are symmetrical and developed equally, and the hollows in the enamel between them have the shape of a horseshoe. The root is the same as that of the first premolar. A person in the dentition there are 8 premolars, four on each side (on the lower and upper jaws).
Molars
In the upper jaw, the first molar is the largest. Its crown resembles a rectangle, and the chewing surface presents a diamond shape with 4 tubercles. This molar has three roots: one straight - the most powerful, and two cheek - flat, deviated in the posterior direction.
During the closing of the jaws, the first molars resist and form a kind of "limiter”, Because of this, they undergo significant loads throughout a person’s life.
Second molar has smaller sizes. The roots are the same as in the first molar. The structure completely coincides with the location of the premolars described above.
On the lower jaw, the first molar for chewing food has five hillocks. This molar two roots - front with two channels, rear - with one. At the same time, the front root is larger than the back. On the lower jaw, the second molar is similar in structure to the first. The number of molars in humans is the same as premolars.
The third molar is called "wisdom tooth"And there are four people in the dentition, two in each jaw. On the jaw from below, the third molar has many variations in the development of tubercles. As a rule, there are five of them. But, in general, a person has the structure of the “wisdom tooth” the same as the structure of the second molar, but the root usually resembles a very powerful and short stem.
Baby teeth
The histological and anatomical structure of the milk tooth is similar to the structure of the primary one, however, there are certain differences:
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The enamel is thinner, and the dentin composition has less mineralization, unlike permanent teeth, so children often develop caries. - The size of the crown is much smaller.
- Hillocks on the cutting and chewing surfaces are not so pronounced.
- The volume of the root canal and the pulp of the milk tooth is much larger in contrast to the volumes of the primary tooth, therefore it is more exposed to the appearance of various inflammations.
- The roots are arched toward the lips, they are not as strong and long as the roots of the molars.
- The incisors are more convex.
In the end, I would like to note that, naturally, the layout of the teeth in the jaw, their structure, closure have an individual character for each specific person. But each person's dental-maxillary apparatus performs vital functions throughout life, therefore, after a period of time, the dental structure changes.
We must not forget that in dentistry, many pathological processes appear in childhood, because you need to monitor the condition of the teeth since childhood. This will help to avoid problems in the future.
Despite the seeming simplicity, teeth are pretty fragile and complex system, with a multilayer structure, where each layer and element has its specific purpose, as well as certain properties. And the factor that the change of teeth takes place only once in a lifetime makes the structure of the jaw of a person different from the anatomy of the jaw of other representatives of the fauna.
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