Teeth are not only bone formations for the mechanical processing of food, but also an indicator of human health and well-being.
Since ancient times, people have been forced to eat tough food that needs careful grinding and processing. And it was white, even teeth with pink gums that always testified that a person eats qualitatively and variedly.
Scheme
Human teeth are made up of three elements:
- Crown. The uppermost visible part, which completely or partially protrudes above the alveolus after eruption;
- Neck. A narrower area located in the gum between the main crown and the root.
- Root. The lowest part, located in the alveolus. The pulp of the root contains interweaving of nerves and blood vessels. With the help of the periosteum, the roots are tightly fixed in the alveolar socket. Depending on the functions performed by the tooth and the 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 dentin, which makes up most of its mass. From a chemical point of view, dentin is collagen impregnated with various salts, phosphorus and other minerals.
Photo: diagram of the structure of the teeth and jaw of a person
The crown is covered with enamel on top. Due to the fact that the basis of the crown is inorganic compounds, its strength is close to diamond. Metabolic processes occur only in a thin skin, tightly enveloping the surface of intact enamel.
The fixation of the tooth occurs with the help of a "special cement" that covers the root. In its structure, cement is very close to the structure of bone tissue. Blood flow occurs through the branches of the external carotid artery, tightly intertwined. The outflow of venous blood occurs through the vessels directly connected with the blood circulation of the brain.
Such blood circulation, in turn, carries a danger: if the initial infection is localized in the oral cavity, it can enter the dura mater through these vessels and cause a number of serious diseases.
In an adult, the row consists of two arches, each of which contains from fourteen to sixteen teeth. In children under twelve years old, the row looks a little different - they, as a rule, have only twenty dairy.
The external similarity of the structure of the upper and lower jaws does not indicate their identity, so you should familiarize yourself with their structure and distinctive features.
In the following video you can clearly see all of the above:
upper jaw
central incisor characterized by the presence of a flat shape, beveled cutting edge and a single root. The frontal part of the incisor is convex and contains three small tubercles.
Appearance lateral incisor identical to the central one. But due to the fact that the central tubercle is large and stands out much stronger, the cutting edge itself acquires a convex streamlined shape.
Fang- an element inherited by a person from predatory representatives of the fauna. There is only one voluminous tubercle on the canine crown. With the help of a furrow passing through the inner part, the canine is, as it were, divided into two parts.
Small molars(in dentistry called premolars). Unlike frontal, premolars are characterized by a more square shape. The roots, although flattened, are already beginning to fork.
Large molars (aka molars)- are the largest in the entire series and are responsible for the direct grinding of food. The first molar has a rectangular shape with four tubercles, which allows you to chew food as efficiently as possible. The second molar is somewhat smaller in size, but in terms of functionality and root structure, it practically does not differ from its predecessor.
The third molar, also called the wisdom tooth, grows much later than the others. Sometimes it may not erupt at all, which is not very scary, since it does not perform any important functions and is more of a rudimentary organ.
Lower jaw
The name and number of teeth of the upper and lower jaws are the same, but they have differences in structure and functional features.
Anterior incisors much smaller than their counterparts above. The outer surface has two edges: sharp and blunt. The roots are shallow and not large.
lower fangs practically do not differ from those located on top, they only have narrower edges.
Molars and premolars the lower jaw has a different number of tubercles for chewing food, as well as roots and canals in them. Unlike the upper molars, the lower ones have one less root.
Anatomy of molars and premolars
Molar teeth in dentistry are divided into large - molars, and small - premolars. And their structure in humans is very different from the front.
premolars
A person has two small molars on the left and right sides. In the first premolar, the central part of the chewing surface has a long shape, while the far one is shorter and larger.
The second premolar retains all the features of the first, but it is more massive. The upper premolar is slightly smaller than its lower counterpart.
molars
Depending on the individual anatomical features, the number of molars in a person can vary from eight to twelve. Due to the structural features of the jaw, the molars gradually decrease from the center to the edges.
Molar crowns are large, with a pronounced square or even triangular contact surface. From above, there are from three to five chewing tubercles, allowing the molars to fully fulfill their functional duties - the primary processing of food.
The upper molars are characterized by the presence of three roots, two of which are directed towards the cheek, and one towards the tongue. The lower molars have only two roots: back and front. In the extreme molars, the roots sometimes grow together. Third molars also have a highly unpredictable crown shape, which depends on the structure of the skull and jaw.
Incisors and fangs
Dentists divide the frontal teeth of a person into canines and incisors.
incisors
The incisors are two teeth located in the upper and lower jaw arches. The crown has a narrow, flattened shape with a sharp edge, as it is designed to cut off pieces of food, which are subsequently chewed by molars and premolars.
The incisors of the upper jaw are much wider and more massive, while the lower ones are almost two times smaller. The roots are single and flat, especially for the incisors located below. The upper part of the roots deviates to the side.
fangs
Canines are located directly behind the incisors in the upper and lower jaw arches. Their distinctive feature is that both cutting edges converge at an angle at one point, forming such a recognizable shape. The fangs have one long root with grooves in the lateral part.
The upper canine is larger and more massive, while the lower canine is less pronounced. The fangs located below have a shorter and even cutting edge, narrow longitudinal ridges. The roots are noticeably shorter compared to the upper ones, they have pronounced grooves.
Wisdom teeth
a - vestibular surface; b - mesial surface; c - lingual surface; g - slice of the "eight"; d - mesiodistal cut; 1, 2, 3 - transverse section: in the plane of the crown, in the middle and upper part of the root
Wisdom teeth, or third molars as they are properly called, can erupt at any age, and not necessarily all. But at the same time, even if they never appeared, remaining in their infancy, this is not a deviation from the norm.
Third molars are among the most problematic human teeth. They are located at the end of the row on both sides, and there are four of them in total. The structure of the third molars is no different from the structure of the other large molars. But at the same time, there are some peculiarities:
- the wisdom tooth is the last in the row, and is not sandwiched between its neighbors;
- at the location of the third molar, children do not have milk teeth that prepare the ground for its eruption, which makes this process more unpleasant and painful;
- the roots of the third molars often grow together into one large one, which may have an irregular conical shape;
- The crown does not necessarily erupt completely and has a variety of shapes.
Typically, third molars grow between the ages of eighteen and twenty-five. But sometimes they may appear much later, or even not appear at all. Such unerupted teeth are called impacted or semi-impacted if the crown has appeared only partially.
Problems with the growth of wisdom teeth are caused by evolutionary changes in the skull. In the jaw of a modern person, they are a rudimentary organ, and often there is simply no necessary space for their normal development.
Baby teeth
Their formation in a child begins to occur even in the womb at the twelfth week.. As a rule, the incisors, canines, and only at the very end of the molars begin to appear first in a child.
The timing of this process is purely individual and may vary, but in most cases, the formation of a milk bite begins at the age of seven months and ends at three to four years. By this time, the child should have twenty milk teeth.
Compared to permanent teeth, milk teeth have their own characteristics:
- smaller sizes;
- fewer masticatory tubercles;
- roots diverge.
Despite this, milk and permanent teeth have the same number of roots.
The milk row in the jaw consists of ten teeth: four large molars, four incisors and two canines. At the age of six or seven years, milk teeth begin to fall out and are replaced by permanent ones.
First of all, there is a change in the large molar, and the final formation of the row ends by the age of twelve or fourteen, with the exception of the third molar.
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Teeth are an integral part of the chewing and speech apparatus and are ossified papillae of the oral mucosa.
An adult has 32 teeth. In the process of life, their change occurs twice.
The anatomy of the teeth of the upper and lower jaws has a slight difference, consisting in the shape of the crowns, the number and structure of the roots.
Anatomy of teeth
In humans, teeth are located in the cells of the alveolar processes of the jaws, which are located in the oral cavity.
:- Crown - is the most massive part, protrudes above the alveolus, and forms rows (upper and lower).
- Neck - located between the root and the crown and in contact with the mucous membrane of the oral cavity.
- Root - has an apex through which arteries supplying nutrients, veins, lymphatic vessels, providing an outflow of excess fluid, nerves enter the tooth. The root is inside the alveoli.
The crown is covered with enamel and the root with cement.
Inside the tooth there is a cavity filled with pulp. By structure, it is a loose connective tissue. and performs an important function, it contains nerves and blood vessels.
The basis of the tooth is dentin:
- Primary - formed before eruption.
- Secondary - throughout the life of the tooth.
- Tertiary - for injuries and injuries.
The cavity of the tooth is subdivided into the cavity of the crown and the canal of the tooth root. In accordance with the cavity, the pulp of the crown and the pulp of the root of the tooth are isolated.
Enamel is 97% inorganic and 3% water. Of all the tissues of the human body, it is the hardest, this feature is directly related to its chemical composition. The thickness of the enamel in various places of the crown ranges from 0.1 mm to 2.5 mm. The color changes from yellow to grayish-white, which directly depends on the transparency of the enamel.
Anatomical structure of the tooth
The more transparent the enamel, the more the dentin, which has a yellow color, is translucent. Transparency is characterized by its degree of mineralization and homogeneity.
Enamel is covered with cuticle. The cuticle is a thin, strong shell, devoid of minerals. The main function of the cuticle is to protect the enamel from harmful substances. However, even enamel is prone to decay (caries) with improper care.
The natural environment of the oral cavity is alkaline. After each meal, the breakdown of carbohydrates begins with the participation of various bacteria, the products of which are acids.
After eating, the acidity of the oral cavity increases, which adversely affects the enamel. Therefore, it is necessary to remember the rules of personal hygiene and timely care for the oral cavity.
Types of teeth by main function
By shape, the teeth are divided into:
- incisors;
- fangs;
- small and large indigenous.
The structure of the teeth
There are 4 incisors in the mouth- a pair on the upper and lower jaw. The incisors are chisel-shaped. The function of the incisors is to bite off food. The crown of the upper incisors is much wider than the lower, the root is longer. Incisors have 1 root. The root of the mandibular incisors is compressed laterally.
Humans have 2 canines in each dentition. They have a conical shape, 2 cutting edges. The root is slightly longer than that of the incisors, compressed from the sides. The main function of the fangs is biting off and chewing more solid large food. The upper fangs are larger than the lower ones, and the cutting edge is sharper.
Small molars (premolars) have 1 root, which splits at the end. There are 2 tubercles on the crown for better chewing of food. Often, small molars are called "bicushioned", there are 8 units in the oral cavity.
Large molars (molars) located 6 on each jaw, have a cuboid shape. Their size decreases from front to back. Unlike premolars, they have 4 tubercles and several roots. The upper teeth have 2, and the lower 3 roots. The last molars erupt by the age of 20-30. And sometimes they don't exist at all. They are called wisdom teeth. Their peculiarity lies in the fact that all the roots merge into one, - a conical shape. The main function of molars and premolars is the quality of chewing food.
Change of teeth in humans
There are 2 types of teeth replacement. Milk teeth are formed in the womb at about 7 weeks of gestation, and erupt between the ages of 6 months and 2.5 years. The timing of a child's teething depends on heredity. If the parents' teeth erupted quite late, most likely the baby will have the same thing.
In a healthy child:
- middle incisors;
- lateral incisors;
- first indigenous;
- fangs;
- second roots.
Interchangeable bite
In some diseases (for example, rickets) is violated. The number of milk teeth in a child is 20. Unlike permanent ones, they are not so strong, have a yellowish color, and are smaller in size. Despite the fact that milk teeth are replaced by permanent ones, they need proper care and timely treatment.
Permanent teeth erupt at the age of 6-14 years. The exception is eights.
dental formula
Dental formula - a graphic representation of the position of the teeth in the alveolar processes of the jaws. It consists of 4 squares separated by a vertical and a horizontal line.
The horizontal line conditionally divides the upper and lower jaws, the vertical line into the right and left halves. It is customary to record the location of the teeth in a person facing the researcher.
An example of a dental formula
Bite
For a number of reasons, a person may have an abnormal bite (the position of the dentition when the jaws are fully closed).
There are two types of bite:
- correct (physiological) - the position of the dentition in which the upper jaw overlaps the lower by 1/3, and the molars fully interact with each other;
- incorrect (malocclusion) - occurs under the influence of congenital or acquired factors.
Prevention of dental diseases
If you do not properly care for your teeth, a large number of dental diseases occur. The most common disease is caries. Caries occurs due to damage to the enamel. In advanced form, caries turns into pulpitis - inflammation of the pulp, which contains blood vessels and nerves. Negligent attitude to the health of the teeth can lead to their removal.
Therefore, a number of rules should be observed:
- Be sure to brush your teeth in the morning and evening.
- Use daily.
- Use fluoride-containing dental products, including fluoride toothpaste.
- Try to brush your teeth after every meal. If this is not possible, use mouthwash or chewing gum.
- Stick to proper nutrition.
- Visit the dentist regularly.
It is especially important to monitor the health of the teeth of pregnant women, since during development the child needs a large amount of calcium, which is often taken from the enamel of a pregnant woman.
Changes in the quantitative composition of enamel can lead to rapid. There is a misconception that pregnant women should not receive dental treatment. It is allowed to fill and remove teeth during pregnancy, but it is advisable to refuse teeth whitening.
Dental health has a great impact on human life. Diseases of a dental nature negatively affect the state of the whole organism, therefore, one must take a responsible attitude to the oral cavity, do not forget about personal hygiene and timely visits to the dentist.
Related video
Healthy teeth are an adornment of a person. A snow-white smile, even bite and pink gums indicate that a person has good health, and is generally considered a sign of success.
Why did it happen and why is the teeth given such attention?
Teeth are special bone formations that carry out the primary mechanical processing of food.
Since ancient times, a person has been accustomed to eat fairly hard food - the fruits of plants, cereals, meat.
Such food requires good effort to process, and therefore healthy teeth have always been an indicator that a person eats well and varied.
Diagram of the structure of human teeth
The structure of the human molar
The first thing you need to know about teeth is that these organs are the only ones in the human body that cannot be restored.
And their seeming fundamentality and reliability are very quickly violated by poor care and bad habits.
And if the primary, milk, teeth are fragile precisely because of their temporary purpose, then the indigenous ones are given to a person once and for life.
In general, all human teeth are divided into the following types:
- incisors (central and lateral, also called medial and lateral);
- fangs;
- small molars, or premolars;
- large molars, or molars (these also include wisdom teeth that grow in a person at a young or mature age).
Usually their location on both jaws is recorded using the so-called dental formula.
For milk and molars, it differs only in that milk teeth are usually indicated using Latin numerals, and molars - Arabic.
The dental formula of an average adult looks like this: 87654321 | 12345678.
The teeth are indicated by numbers - a person should have two incisors, one canine, 2 premolars and three molars on each side on each jaw.
As a result, we get the total number of teeth of a healthy person - 32 pieces.
In children who have not yet replaced their milk teeth, the dental formula looks different, because there are about 20 of them in total.
Usually milk teeth grow by 2.5-3 years, and by 10-11 they are already completely replaced by molars. Understand, maybe at different ages.
Not all people can boast a smile of 32 teeth. The so-called third molars, or wisdom teeth, can grow in adulthood, and then not all 4, but may even remain in their infancy for life, and then there will be 28 teeth in the mouth. What to do if a wisdom tooth hurts, read in.
At the same time, the structure of the teeth of the upper and lower jaws has its own differences.
The structure of the teeth of the upper jaw
central incisor- chisel-shaped tooth, with a flattened crown. It has one cone-shaped root. The part of the crown that faces the lips is slightly convex. There are three tubercles on the cutting edge, and it is somewhat beveled on the outside.
Two, or side incisor, also has the shape of a chisel and has three tubercles on the cutting edge, like the central incisor. But its cutting edge itself has the shape of a tubercle, due to the fact that the central, medial tubercle is most clearly expressed on it. The root of this tooth is flattened in the direction from the center to the periphery. Often its upper third has a backward deviation. From the side of the cavity of the tooth there are three horns of the pulp, corresponding to the three tubercles of the outer edge.
Fang- a tooth with a distinct convex front side. A groove runs along the lingual side of the canine, dividing the crown in two, with the half located further from the center having a large area. This tooth has one tubercle on the cutting part. It is she who gives the fang a completely recognizable shape. In many people, this shape closely resembles the similar teeth of predators.
Next on the upper jaw is first premolar, indicated by the number 4 on the dental formula. Unlike the canine and incisors, it has a prismatic shape with convex buccal and lingual surfaces. It also has two tubercles on the chewing surface - buccal and lingual, of which the first is much larger in size. Furrows pass between the tubercles of the tooth, which are interrupted by enamel rollers, not reaching the edge of the tooth. The root of the first premolar is flattened, but it already has a forked shape and is also divided into the buccal and lingual parts.
Second premolar has a similar shape to the previous tooth. It differs from the first premolar in a much larger area of the buccal surface of the tooth, as well as in the structure of the root. It is cone-shaped and compressed in the anteroposterior direction in the second premolar.
The largest tooth of the upper jaw is the first molar, or, as it is also called, the large molar. Its crown is like a rectangle, and the chewing surface is diamond-shaped. It has as many as four tubercles responsible for chewing food. An H-shaped fissure passes between the tubercles. This tooth has three roots, of which the palatine is straight and the most powerful, and the two buccal are flat and deviated in the anteroposterior direction.
second molar slightly smaller than the first one. It has a cubic shape, and the fissure between its tubercles resembles the letter X. The buccal tubercles of this tooth are better expressed than the lingual ones. But the roots of this tooth have the same shape and properties as its predecessor.
third molar, or a wisdom tooth, does not grow in everyone. In form and properties, it is similar to the second, the differences exist only in the form of the root. At the third molar, it is often a spliced short powerful trunk.
The structure of the teeth of the lower jaw
The names of the teeth of the lower jaw of a person generally coincide with their antagonists in the upper dentition. But their structure and properties have a number of differences.
The mandibular central incisor is the smallest tooth. Its labial surface is slightly convex, while its lingual surface is concave. In this case, the marginal ridge is weakly expressed. The three cusps of this tooth are weakly expressed, as are the margins. The root is very small, flat.
The lateral incisor is slightly larger than the central incisor, but still remains a small tooth. Its crown is very narrow, chisel-shaped, curved towards the lips. The cutting edge of this tooth has two angles - the medial one is sharper, and the lateral one is blunt. Root one, flat, has longitudinal grooves.
The canine of the lower jaw is similar to its upper counterpart. It also has a diamond shape, convex on the side of the tongue. But, unlike the upper canine of the same kind, this tooth has a narrower shape. All its faces converge on one central tubercle. The root of the tooth is flat, deflected inwards.
The first lower premolar has only two cusps. Its chewing surface is beveled towards the tongue. The shape of this tooth is rounded. The root of the first premolar is one, flat and slightly flattened laterally. Grooves run along its frontal surface.
The second premolar of the lower jaw is larger than the first one due to the fact that both of its tubercles are equally developed. They are located symmetrically, and the fissure between them has the shape of a horseshoe. This tooth has the same root as its predecessor.
The first molar has a cubic shape and as many as five tubercles for chewing food - three of them are located on the buccal side, and two more on the lingual side. Due to the number of tubercles, the fissure between them resembles the letter J. The first molar has two roots. The rear is slightly shorter than the front and has only one channel. There are already two canals at the anterior root - anterior cervical and anterior lingual.
The second molar of the lower jaw is similar to the first cubic shape of the crown and roots.
The third molar is also similar to them. Its main difference is in the variety of tubercles. There are a lot of types of their development in this wisdom tooth.
Anatomical structure of the tooth
This is with regard to the structure of the jaw and individual teeth. But the anatomical structure of the tooth implies the presence of the following parts:
- crowns,
- necks,
- root.
Crown name the part of the tooth that is located above the gum. That is visible to everyone.
Tooth root located in the alveolus - a recess in the jaw. The number of knights, as becomes apparent from the previous sections of the article, is not always the same. The root is fixed in the alveolus with the help of connective tissue formed by bundles of collagen fibers. The neck is the part of the tooth that is located between the root and the crown.
If you look at the tooth in section, you can see that it consists of several layers.
Outside, the tooth is covered with the hardest tissue in the human body - enamel. In the teeth that have just appeared, it is still covered on top with a cuticle, which over time is replaced by a membrane derived from saliva - the pellicle.
Histological structure of the tooth
Under the enamel is a layer of dentin - the base of the tooth. In its cellular structure, it is similar to bone tissue, but in terms of properties it has a much larger margin of safety due to increased mineralization.
In the region of the root, where there is no enamel, the dentin is covered with a layer of cementum and permeated with collagen fibers, which hold the periodontium together.
Connective tissue is located in the very center of the tooth - pulp. It is soft, permeated with many blood vessels and nerve endings. It is her defeat by caries or inflammatory processes that causes the very unbearable toothache.
The structure of milk teeth in children
Despite the fact that milk teeth are smaller than molars, and their structure is different, they are very similar in shape and purpose.
The main difference is that they almost always have a smaller size than their native followers.
The crowns of milk teeth have enamel and dentin with a lower degree of mineralization than those of molars, and therefore are more susceptible to caries.
At the same time, the pulp in milk teeth occupies a larger volume than in molars, and is also more susceptible to all kinds of inflammation and disease processes.
Even on their surface, tubercles of the cutting and chewing parts are poorly expressed.
At the same time, the incisors of the milk teeth are more convex than those of the permanent ones, and the tops of their roots are bent to the labial side.
Also, all milk teeth are distinguished by not too long and strong roots, due to which the change of teeth in childhood is not too painful.
All these features of their structure lead to the fact that 80% of all pathologies associated with dentistry develop in childhood. Therefore, it is very important to monitor the sanitation of milk teeth from childhood in order to avoid problems with permanent ones in the future.
Teeth are a very complex system of the human body. They carry a huge burden throughout their lives. Moreover, each tooth has its own shape, the most suitable for its purpose, the number of tubercles designed for efficient food processing, its own root system and their location in the alveolus.
In addition, the internal structure of the teeth is also not simple. They consist of several layers that have their own purpose and properties.
In particular, tooth enamel is the hardest tissue in the entire body, which makes it easy to process food.
In general, despite the apparent strength, teeth are a very fragile system that requires constant care and attention to the processes taking place in them, due to the fact that of all human organs they are the only ones that do not have the ability to self-heal, and therefore timely sanitation will help preserve them. for a long time healthy, strong and beautiful.
Pictures, photos of the structure of a human tooth:
tooth anatomy
Dentistry
human teeth
Tooth consists mainly of dentin with a cavity, covered on the outside with enamel and cement. The tooth has a characteristic shape and structure, occupies a certain position in the dentition, is built from special tissues, has its own nervous apparatus, blood and lymphatic vessels. Normally, a person has from 28 to 32 teeth. The absence of third molars, called “wisdom teeth”) is the norm, and the 3rd molars themselves are already considered atavism by an increasing number of scientists, but this is currently a moot point.
Inside the tooth is loose connective tissue, permeated with nerves and blood vessels (pulp). Distinguish milk and permanent teeth - temporary and permanent bite. In temporary bite there are 8 incisors, 4 canines and 8 molars - a total of 20 teeth. The permanent bite consists of 8 incisors, 4 canines, 8 premolars and 8-12 molars. In children, milk teeth begin to erupt at the age of 3 months. Between the ages of 6 and 13, milk teeth are gradually replaced by permanent ones.
In rare cases, additional, supernumerary teeth (both milk and permanent) are observed.
Tooth structure
Dental anatomy is a branch of anatomy that deals with the structure of teeth. The development, appearance, and classification of teeth are the subject of this section, but bite or tooth contact is not. Dental anatomy can be considered as a taxonomic science, as it deals with the classification of teeth, their structure and naming. This information is then put into practice by dentists during treatment.
The tooth is located in the alveolar process of the upper jaw or in the alveolar part of the lower jaw, and consists of a number of hard tissues (such as tooth enamel, dentin, dental cement) and soft tissues (dental pulp). Anatomically, the crown of the tooth (the part of the tooth protruding above the gum), the root of the tooth (the part of the tooth located deep in the alveolus, covered by the gum) and the neck of the tooth are distinguished - the clinical and anatomical necks are distinguished: the clinical neck corresponds to the edge of the gum, and the anatomical is the place where the enamel passes into the cement, which means that the anatomical neck is the actual site of transition of the crown to the root. It is noteworthy that the clinical neck shifts with age towards the root apex (apex) (since gum atrophy occurs with age), and the anatomical neck moves in the opposite direction (since the enamel becomes thinner with age, and in the neck area it can be completely worn out due to the fact that in the region of the neck, its thickness is much less). Inside the tooth there is a cavity, which consists of the so-called pulp chamber and the root canal of the tooth. Through a special (apical) opening located at the top of the root, arteries enter the tooth, which deliver all the necessary substances, veins, lymphatic vessels, which ensure the outflow of excess fluid and participate in local defense mechanisms, as well as nerves that innervate the tooth.
Embryology
Orthopantomogram of teeth
The development of teeth in the human embryo begins at about 7 weeks. In the area of future alveolar processes, a thickening of the epithelium occurs, which begins to grow in the form of an arcuate plate into the mesenchyme. Further, this plate is divided into anterior and posterior, in which the rudiments of milk teeth are formed. Tooth germs gradually separate from the surrounding tissues, and then the components of the tooth appear in them in such a way that epithelial cells give rise to enamel, dentin and pulp are formed from the mesenchymal tissue, and cement and root sheath develop from the surrounding mesenchyme.
Tooth regeneration
X-ray (from left to right) of the third, second and first molars in various stages of development
Human teeth do not regenerate, while in some animals, such as sharks, they are constantly updated throughout life.
In a recent study led by G. Fraser from the University of Sheffield, the influence of various genes on the formation of the dental plate in humans and sharks (in which teeth grow continuously throughout life) was studied. The group was able to identify a clear set of genes responsible for tooth differentiation and growth. It turned out that these genes in humans and sharks are largely identical, but in humans, after the formation of molars, for unknown reasons, the plate is lost. Scientists believe that the discovery of the genes responsible for the growth of teeth will serve as the first step in the search for the possibility of their regeneration.
Biochemistry of teeth
Tooth structure
Teeth (Latin dentes) are organs that are located in the alveolar processes of the upper and lower jaws and perform the function of primary mechanical processing of food. The jaws of an adult contain 32 permanent teeth. In their structure, dental tissues are close to bone tissue, the main structural and functional components of the tooth are derivatives of connective tissue.
In each tooth, there is a crown of the tooth (corona dentis), which protrudes freely into the oral cavity, the neck of the tooth covered by the gums and the root of the tooth (radix dentis) fixed in the bone tissue of the alveoli, which ends with an apex (apex radicis dentis).
Comparative characteristics of biochemical
composition of dental tissues.
Tooth stone.
The tooth is built from three balls of calcified tissues: enamel, dentin, and cementum. The cavity of the tooth is filled with pulp. The pulp is surrounded by dentin, the underlying calcified tissue. On the protruding part of the tooth, the dentin is covered with enamel. The roots of the teeth sunk into the jaw are covered with cementum.
The roots of the teeth, which are immersed in the alveolar sockets of the upper and lower jaws, are covered with periodontium, which is a specialized fibrous connective tissue that holds the teeth in the alveoli. The main periodontium is made up of periodontal ligaments (ligaments), which connect the cementum with the bone matrix of the alveolus. From a biochemical point of view, periodontal ligaments are based on type I collagen with some type III collagen. Unlike other ligaments of the human body, the ligamentous apparatus that forms the periodontium is highly vascularized. The thickness of the periodontal ligaments, which in an adult is approximately 0.2 mm, decreases in the elderly and senile age.
These components of the tooth differ in functional purposes and, accordingly, in biochemical composition, as well as in metabolic features. The main components of tissues are water, organic compounds, inorganic compounds and mineral components, the content of which can be given in the following tables:
(% wet weight of the woven component):
NECROSIS OF THE TEETH
| Composite tooth | Enamel | Dentine | Pulp | Cement |
|---|---|---|---|---|
| Water | 2,3 | 13,2 | 30-40 | 36 |
| organic compounds | 1,7 | 17,5 | 40 | 21 |
| inorganic compounds | 96 | 69 | 20-30 | 42 |
Biochemical composition of human tooth tissues
(% dry weight of the fabric component):
Remineralization of teeth.
| Ca | 36,1 | 35,3 | 35,5 | 30 |
|---|---|---|---|---|
| mg | 0,5 | 1,2 | 0,9 | 0,8 |
| Na | 0,2 | 0,2 | 1,1 | 0,2 |
| K | 0,3 | 0,1 | 0,1 | 0,1 |
| P | 17,3 | 17,1 | 17,0 | 25,0 |
| F | 0,03 | 0,02 | 0,02 | 0,01 |
Organic components of the tooth
Leave your teeth cleaning to the professionals.
The organic components of the tooth are proteins, carbohydrates, lipids, nucleic acids, vitamins, enzymes, hormones, organic acids.
The basis of the organic compounds of the tooth, of course, are proteins, which are divided into soluble and insoluble.
Soluble proteins of dental tissues:
Named tooth decay
caries, begin by dissolving
minerals in the tooth.
albumins, globulins, glycoproteins, proteoglycans, enzymes, phosphoproteins. Soluble (non-collagenous) proteins are characterized by high metabolic activity, perform enzymatic (catalytic), protective, transport and a number of other functions. The highest content of albumins and globulins is in the pulp. The pulp is rich in enzymes of glycolysis, the tricarboxylic acid cycle, the respiratory chain, the pentose phosphate pathway for carbohydrate digestion, and protein and nucleic acid biosynthesis.
Soluble enzyme proteins include two important pulp enzymes - alkaline and acid phosphatases, which are directly involved in the mineral metabolism of tooth tissues.
It manifests itself and is characterized by inflammation of the soft tissues and mucous membranes.
Biochemical characteristics of individual
tissue components of the tooth
Enamel
Enamel is the hardest tissue in the human body.
95% mineral.
the hardest mineralized tissue that sits on top of the dentin and outwardly covers the crown of the tooth. Enamel makes up 20-25% of the dental tissue, the thickness of its ball is maximum in the area of chewing peaks, where it reaches 2.3-3.5 mm, and on the lateral surfaces - 1.0-1.3 mm.
The high hardness of the enamel is due to the high degree of tissue mineralization. Enamel contains 96% minerals, 1.2% organic compounds and 2.3% water. Part of the water is in a bound form, forming a hydration shell of crystals, and part (in the form of free water) is filled with microspaces.
The main structural component of enamel are enamel prisms with a diameter of 4-6 microns, the total number of which ranges from 5 to 12 million, depending on the size of the tooth. Enamel prisms are composed of packed crystals, often hydroxyapatite Ca8H2(PO4)6×5H2O. Other types of apatite are poorly represented: hydroxyapatite crystals in mature enamel are approximately 10 times larger than crystals in dentin, cementum, and bone tissue.
As part of the mineral substances of enamel, calcium is 37%, phosphorus - 17%. The properties of enamel largely depend on the ratio of calcium and phosphorus, which changes with age and depends on a number of factors. In adult tooth enamel, the Ca/P ratio is 1.67. In the enamel of children, this ratio is lower. This indicator also decreases with enamel demineralization.
Dentien
These buildups of tartar cause the gum surfaces to recede and the soft dentinal material that covers the roots of the teeth begins to break down.
mineralized, acellular, avascular tissue of the tooth, which forms the bulk of its mass and in structure takes an intermediate position between bone tissue and enamel. It is harder than bone and cement, but 4-5 times softer than enamel. Mature dentin contains 69% inorganic substances, 18% organic and 13% water (which is 10 and 5 times more than enamel, respectively).
Dentin is built from mineralized intercellular substance, pierced by numerous dentinal canals. The organic matrix of dentin makes up about 20% of the total mass and is close in composition to the organic matrix of bone tissue. The mineral basis of dentin is made up of apatite crystals, which are deposited in the form of grains and spherical formations - calcospherites. Crystals are deposited between collagen fibrils, on their surface and within the fibrils themselves.
dental pulp
it is a highly vascularized and innervated specialized fibrous connective tissue that fills the pulp chamber of the crown and root canal. It consists of cells (odontoblasts, fibroblasts, microphages, dendritic cells, lymphocytes, mast cells) and intercellular substance, and also contains fibrous structures.
The function of the cellular elements of the pulp - odontoblasts and fibroblasts - is the formation of the main intercellular substance and the synthesis of collagen fibrils. Therefore, cells have a powerful protein-synthesizing apparatus and synthesize a large amount of collagen, proteoglycans, glycoproteins and other water-soluble proteins, in particular, albumins, globulins, and enzymes. In the dental pulp, a high activity of carbohydrate metabolism enzymes, tricarboxylic acid cycle, respiratory enzymes, alkaline and acid phosphatase, etc. was found. The activity of enzymes of the pentose phosphate pathway is especially high during the period of active production of dentin by odontoblasts.
The pulp of the tooth performs important plastic functions, taking part in the formation of dentin, provides trophism of the dentin of the crown and root of the tooth. In addition, due to the presence of a large number of nerve endings in the pulp, the pulp provides the necessary sensory information to the central nervous system, which explains the very high pain sensitivity of the internal tissues of the tooth to pathological stimuli.
Processes of mineralization-demineralization -
the basis of mineral metabolism of tooth tissues.
The basis of the mineral metabolism of tooth tissues are three interdependent processes that constantly occur in the tissues of the tooth: mineralization, demineralization and remineralization.
Mineralization of the tooth
this is the process of formation of an organic base, primarily collagen, and its saturation with calcium salts. Mineralization is especially intense during teething and the formation of hard tooth tissues. The tooth erupts with non-mineralized enamel!!! There are two main stages of mineralization.
The first stage is the formation of an organic, protein matrix. The pulp plays the leading role at this stage. In pulp cells, odontoblasts and fibroblasts, collagen fibrils, non-collagen proteins proteoglycans (osteocalcin) and glycosaminoglycans are synthesized and released into the cell matrix. Collagen, proteoglycans and glycosaminoglycans form the surface on which the formation of the crystal lattice will take place. In this process, proteoglycans play the role of collagen plasticizers, that is, they increase its swelling capacity and increase its total surface. Under the action of lysosomal enzymes, which are released into the matrix, proteoglycan heteropolysaccharides are cleaved to form highly reactive anions that are able to bind ions Ca2+ and other cations.
The second stage is calcification, deposition of apatites on the matrix. Oriented crystal growth begins at the points of crystallization or at the points of nucleation - in areas with a high concentration of calcium and phosphate ions. The locally high concentration of these ions is provided by the ability of all components of the organic matrix to bind calcium and phosphates. In particular: in collagen, the hydroxyl groups of serine, threonine, tyrosine, hydroxyproline and hydroxylysine residues bind phosphate ions; free carboxyl groups of dicarboxylic acid residues in collagen, proteoglycans and glycoproteins bind ions Ca2+ ; residues of g-carboxyglutamic acid of calcium-binding protein - osteocalcin (calprotein) bind ions Ca2+ . Calcium and phosphate ions are concentrated around the crystallization nuclei and form the first microcrystals.
Toothpastes
An increase in the concentration of the dispersed phase to the limiting possible value in aggregation-resistant suspensions leads to the formation of highly concentrated suspensions, which are called pastes. Like output suspensions, pastes are aggregatively stable in the presence of a sufficient amount of strong stabilizers, when the particles of the dispersed phase in them are well solvated and separated by thin films of liquid, which serves as a disperse medium. Due to the small part of the dispersion medium in the paste, all of it is practically bound in solvate films that separate the particles. The absence of a free sparse vase adds high viscosity and some mechanical strength to such systems. Due to the numerous contacts between the particles in the pastes, the formation of spatial structures can occur and thixotropy phenomena are observed.
The most widely used toothpastes. A bit of history. Our ancestors brushed their teeth with crushed glass, charcoal, and ash. Three centuries ago in Europe they began to brush their teeth with salt, then switched to chalk. Since the beginning of the 19th century, chalk-based tooth powders have been widely used in Western Europe and Russia. Since the end of the 19th century, the world began to switch to toothpaste in tubes. In the 20s of the last century, the search for a replacement for chalk as a dental abrasive began. These searches led to the use of silicon dioxide, which is highly compatible with fluorine compounds and other active ingredients, which have controlled abrasiveness, which makes it possible to create pastes with a wide range of properties. And finally, we got the optimal pH value = 7.
But even now, in some pastes, chalk with a reduced content of aluminum (Al), iron (Fe) and trace elements is used as an abrasive, but with an increased ability to erase.
In addition, some pastes include plantain, nettle and tree extracts, vitamins, ascorbic acid, pantothenic acid, carotenoids, chlorophyll, flavonoids.
All pastes are divided into two large groups - hygienic and therapeutic and prophylactic. The first group is intended only for cleansing the goiter from the plaque of food, as well as giving the oral cavity a pleasant smell. Such pastes are usually recommended for those who have healthy teeth, and also no reason for the occurrence of dental diseases, and who regularly visits the dentist.
The bulk of toothpastes belongs to the second group - therapeutic and prophylactic. Their purpose, in addition to cleaning the surface of the teeth, is to suppress the microflora that causes caries and periodontitis, remineralize tooth enamel, reduce inflammation in periodontal diseases, and whiten tooth enamel.
Allocate anti-caries pastes that contain calcium and fluoride toothpastes, as well as toothpastes with anti-inflammatory action and whitening pastes.
The anti-caries effect is provided by the presence of fluorides (sodium fluoride, tin fluoride, aminofluoride, monofluorophosphate) and calcium (calcium glycerophosphate) in the toothpaste. The anti-inflammatory effect is usually achieved by adding herbal extracts (mint, shavlia, chamomile, etc.) to the toothpaste. Whitening pastes contain sodium bicarbonate, or soda, which has a pronounced abrasive effect. It is not recommended to use such pastes every day due to the risk of damage to the enamel. It is usually recommended to use them 1-2 times a week.
There is also a list of substances that are part of toothpastes. They perform auxiliary functions. So, detergents, among which sodium lauryl sulfate is more common, which is also used in the manufacture of shampoos, cause foaming. Abrasives, among which the most popular are aluminum hydroxide, chalk, sodium bicarbonate, silicon dioxide, clean the surface of the teeth from plaque and microbes. Acidity stabilizers are designed to increase the pH in the mouth because an acidic environment promotes cavities. Other substances that are part of toothpaste improve its consumer properties - thickeners, dyes, solutions, etc.
The main components of toothpastes:
1) abrasive substances;
2) detergents: soap used to be used, now sodium lauryl sulfate, sodium lauryl sarcosinate: the foaminess of the toothpaste and the surface of the tangent substances depend on this component;
3) glycerin, polyethylene glycol - provide elasticity and viscosity of pastes;
4) binders (hydrocolloids, sodium alginate, starch, thick juices, dextrin, pectin, etc.);
5) various additives (plant extracts, salts, etc.).
In the clinical practice of developed countries, synthetic hydroxyapatite is used as a bone tissue substitute. Reducing the sensitivity of teeth, protecting the surface areas of enamel, hydroxyapatite has anti-inflammatory properties, adsorbing microbial bodies, and ahead of the development of purulent-inflammatory processes. In addition, hydroxyapatite stimulates the growth of bone tissue (osteogenesis), provides micro-treatment of bone and dental tissues with calcium and phosphorus ions, “bricking up” microcracks in them. It has high biocompatibility, is devoid of immunogenic and allergic activity. Synthetic hydroxyapatite has very small particle sizes (0.05 microns). Such parameters greatly increase its biological activity, since the size of its molecules is comparable to the size of protein macromolecules.
An effective additive is triclosan, which acts on a wide range of bacteria, fungi, yeasts and viruses. The antimicrobial activity of triclosan is based on a violation in its presence of the activity of the cytoplasmic membrane and the leakage of cellular components of low molecular weight.
The composition of toothpastes also includes carbamide with components such as xylitol, sodium bicarbonate, which are therapeutic and prophylactic additives. This mixture neutralizes the action of acids, mainly lactic, which are produced by plaque bacteria by fermenting carbohydrates found in foods and drinks. Bacteria produce, although in much smaller quantities, other acids such as acetic, propionic, and butyric. The formation of acids leads to a decrease in the pH of plaque: at a pH of less than 5.5, the process of demineralization of tooth enamel begins. The longer the duration of such demineralization, the higher the risk of caries. Penetrating into plaque, urea neutralizes acids, being broken down by bacteria in the presence of the urease enzyme into CO2 And NH3 ; formed NH3 is alkaline and neutralizes acids.
General Functions of the Teeth
Mechanical processing of food
food retention
Participation in the formation of speech sounds
Aesthetic - are an important part of the mouth
Types and functions of teeth
According to the main function, teeth are divided into 4 types:
The incisors are the first teeth that erupt in children and are used to grasp and cut food.
Fangs - cone-shaped teeth that are used to tear and hold food
Premolars (small molars)
Molars (large molars) - the back teeth, which serve to grind food, often have three roots on the upper jaw and two on the lower
Tooth Development (Histology)
Hat Stage
Beginning of the bell stage
Acid phosphatase
has the opposite, demineralizing effect. It belongs to lysosomal acid hydrolases, which enhance the dissolution (absorption) of both mineral and organic structures of tooth tissues. Partial resorption of tooth tissues is a normal physiological process, but it especially increases during pathological processes.
An important group of soluble proteins are glycoproteins. Glycoproteins are protein-carbohydrate complexes that contain from 3-5 to several hundred monosaccharide residues and can form from 1 to 10-15 oligosaccharide chains. Typically, the content of carbohydrate components in a glycoprotein molecule rarely exceeds 30% of the mass of the entire molecule. The glycoproteins of tooth tissues include: glucose, galactose, monose, fructose, N-acetylglucose, N-acetylneuraminic (sialic) acids, which do not have a regular rotation of disaccharide units. Sialic acids are a specific component of a group of glycoproteins - sialoproteins, the content of which is especially high in dentin.
One of the most important glycoproteins of the tooth, as well as bone tissue, is fibronectin. Fibronectin is synthesized by cells and secreted into the extracellular space. It has the properties of a "sticky" protein. By binding to the carbohydrate groups of sialoglycolipids on the surface of plasma membranes, it ensures the interaction of cells between themselves and the components of the extracellular matrix. Interacting with collagen fibrils, fibronectin ensures the formation of the pericellular matrix. For each compound with which it binds, fibronectin has its own, so to speak, specific binding site.
Insoluble proteins in dental tissue
are often represented by two proteins - collagen and a specific structural protein of enamel, which does not dissolve in EDTA (ethylenediaminetetraacetic) and hydrochloric acid. Due to its high stability, this enamel protein acts as the skeleton of the entire molecular architecture of enamel, forming a framework - a “crown” on the tooth surface.
Collagen: structural features,
role in tooth mineralization.
Collagen is the main fibrillar protein of connective tissue and the main insoluble protein in tooth tissues. As stated above, its content is about a third of all proteins in the body. Most collagen is found in tendons, ligaments, skin and tooth tissues.
The special role of collagen in the functioning of the human dentoalveolar system is due to the fact that the teeth in the holes of the alveolar processes are fixed by periodontal ligaments, which are formed precisely by collagen fibers. With scurbut (scurvy), which occurs due to a lack of vitamin C (L-ascorbic acid) in the diet, there are violations of the biosynthesis and structure of collagen, which reduces the biomechanical properties of the periodontal ligament and other periodontal tissues, and, as a result, loosen and fall out teeth. In addition, the blood vessels become brittle, multiple pinpoint hemorrhages (petechiae) occur. Actually, gum bleeding is an early manifestation of scorbut, and violations in the structure and functions of collagen are the root cause of the development of pathological processes in connective, bone, muscle and other tissues.
Carbohydrates of the organic matrix of the tooth
composition of dental tissues.
Periodontal disease is a systemic lesion of the periodontal tissue.
The composition of the organic matrix of the tooth includes the monosaccharides glucose, galactose, fructose, manose, xylose and the disaccharide sucrose. Functionally important carbohydrate components of the organic matrix are homo- and heteropolysaccharides: glycogen, glycosaminoglycans and their complexes with proteins: proteoglycans and glycoproteins.
homopolysaccharide glycogen
performs three main functions in the tissues of the tooth. First, it is the main source of energy for the processes of formation of crystallization nuclei and is localized in the places of formation of crystallization centers. The content of glycogen in the tissue is directly proportional to the intensity of mineralization processes, since a characteristic feature of tooth tissues is the prevalence of anaerobic processes of energy formation - glycogenolysis and glycolysis. Even with sufficient oxygen supply, 80% of the energy needs of the tooth are covered by anaerobic glycolysis, and, accordingly, by the breakdown of glycogen.
Secondly, glycogen is a source of phosphate esters of glucose - substrates of alkaline phosphatase, an enzyme that splits off phosphoric acid ions (phosphate ions) from glucose monophosphates and transfers them on a protein matrix, that is, initiates the formation of an inorganic matrix of the tooth. In addition, glycogen is also a source of glucose, which is converted into N-acetylglucosamine, N-acetylgalactosamine, glucuronic acid and other derivatives that take part in the synthesis of heteropolysaccharides - active components and regulators of mineral metabolism in tooth tissues.
Heteropolysaccharides of the organic matrix of the tooth
represented by glycosaminoglycans: hyaluronic acid and chondroitin-6-sulfate. A large number of these glycosaminoglycans remain in a protein-bound state, forming complexes of varying degrees of complexity, which differ significantly in the composition of the protein and polysaccharides, that is, glycoproteins (there is much more of a protein component in the complex) and proteoglycans, which contain 5-10% protein and 90- 95% polysaccharides.
Proteoglycans regulate the processes of aggregation (growth and orientation) of collagen fibrils, and also stabilize the structure of collagen fibers. Due to their high hydrophilicity, proteoglycans play the role of plasticizers in the collagen network, increasing its ability to stretch and swell. The presence of a high amount of acidic residues (ionized carboxyl and sulfate groups) in the molecules of glycosaminoglycans determines the polyanionic nature of proteoglycans, a high ability to bind cations and thereby take part in the formation of nuclei (centers) of mineralization.
An important component of tooth tissues is citrate (citric acid). The content of citrate in dentin and enamel is up to 1%. Citrate, due to its high ability to complex formation, binds ions Ca2+ , forming a soluble transport form of calcium. In addition to tooth tissues, citrate provides the optimal calcium content in blood serum and saliva, thereby regulating the rate of mineralization and demineralization processes.
Nucleic acids
found mainly in the dental pulp. A significant increase in the content of nucleic acids, in particular RNA, is observed in osteoblasts and odontoblasts during the period of tooth mineralization and remineralization and is associated with an increase in protein synthesis by these cells.
Characterization of the mineral matrix of the tooth
The mineral basis of tooth tissues is made up of crystals of various apatites. The main ones are hydroxypatite Ca 10 (PO4 )6 (OH)2 and octalcium phosphate Ca 8 H2 (PO4 )6 (OH)2× 5H 2 O . Other types of apatite that are present in the tissues of the tooth are listed in the following table:
| Apatite | Molecular formula |
|---|---|
| Hydroxyapatite | Ca10(PO4)6(OH)2 |
| Octalcium phosphate | Ca 8 H2 (PO4 )6 (OH)2× 5H 2 O |
| Carbonate apatite | Ca 10 (PO4 )6 CO 3 or Ca 10 (PO4 )5 CO 3(OH) 2 |
| Chloride apatite | Ca 10 (PO4 )6 Cl |
| Strontium apatite | SrCa 9 (PO4)6 (OH) 2 |
| Fluorapatite | Ca 10 (PO4 )6 F 2 |
Separate types of tooth apatites differ in chemical and physical properties - strength, ability to dissolve (destroy) under the action of organic acids, and their ratio in the tissues of the tooth is determined by the nature of nutrition, the provision of the body with microelements, etc. Among all apatites, fluorapatite has the highest resistance. The formation of fluorapatite increases the strength of enamel, reduces its permeability and increases resistance to cariogenic factors. Fluorapatite is 10 times worse soluble in acids than hydroxyapate. With a sufficient amount of fluoride in the human diet, the number of cases of caries is significantly reduced.
Oral hygiene
Main article: Teeth cleaning
Hygiene oral cavity is a means of preventing dental caries, gingivitis, periodontal disease, bad breath (halitosis) and other dental diseases. It includes both daily cleaning and professional cleaning performed by a dentist.
This procedure involves the removal of tartar (mineralized plaque) that can form even with thorough brushing and flossing.
To care for the first teeth of a child, it is recommended to use special dental wipes.
Items for personal hygiene of the oral cavity: toothbrushes, dental floss (flos), tongue scraper.
Hygiene products: toothpastes, gels, rinses.
Enamel is not capable of regeneration. It has an organic matrix on which inorganic apatites seem to be attached. If apatites are destroyed, then with an increased supply of minerals they can be restored, but if the organic matrix is destroyed, then restoration is no longer possible.
When teething, the crown of the tooth is covered on top with a cuticle, which soon wears out without doing anything useful.
The cuticle is replaced by a pellicle - a dental deposit, consisting mainly of saliva proteins, which have an opposite charge to enamel.
The pellicle performs a barrier (skip of mineral components) and cumulative (accumulation and gradual release of enamel calcium) function.
The role of the pellicle in the formation of dental plaque (helps to attach) with the further occurrence of caries is noted.
See also
animal teeth
dental formula
Tooth Fairy
Thirty-three (film)
Dental prosthetics(8, 9, 10, 11) are divided depending on the functions they perform: incisors (11), canines (10), small molars (9), large molars (8). Teeth appear in a person twice in a lifetime, the first ones are milk teeth, they appear in babies from six months to two years, there are only 20 of them. The second time teeth appear in children at the age of 6-7 years, and wisdom teeth after 20 years, there are only 32 of them.
The elastic should be tight enough so that the flashlight does not spontaneously come off from the recoil of a shot or when pulled out of the grass.
The described mounting system is in a sense universal - the installation location can be chosen based on personal preferences. On pneumatics, the bracket can be fastened with winding, clamps, and other methods.
If you make a special lodgement, for example, on the forearm, then the mount can be installed on it. In this case, so that there are no hooks, it is better to use the “mother” on the gun and the lodgement. The result will be a universal lighting system, with the ability to quickly rearrange it to the right “now” place.
The design has been tested in operation and proved to be the best.
Teeth are our tools that carry out the primary mechanical processing of food. Since ancient times, the presence of healthy teeth meant a higher ability to survive, since the loss of the ability to chew hard and rough food could threaten starvation.
The anatomy of the tooth tells us that this is a formation of tissues special for their function, which have their own nervous and circulatory apparatus. Normal teeth should be. Alas, without outside interference, they are replaced only once in a lifetime, when the molars erupt instead of the falling milk teeth.
Tooth germs are formed in the fetus already in first trimester of pregnancy, during the 7th week of development. At the same time, at the site of the future alveolar processes, the epithelial tissue thickens and, forming a symmetrical arc, grows into the depth of the mesenchyme. Subsequently, secondary plates are formed under it, located perpendicularly.
In the rudiments of teeth, meanwhile, from epithelial cells tooth enamel begins to form. With the growth of the dental plate, the enamel organs are in front and separate from it. It is then that the components of the future tooth are formed.
What we see when we smile is just a crown of a tooth
With normal human tooth anatomy, the epithelium is transformed into enamel, and the mesenchymal tissue forms dentin and pulp, a cement sheath appears that protects the tooth root (see photo). The rudiments themselves remain in the alveolar processes, waiting for the time of its eruption.
According to their structural parts, teeth are usually divided into crown, neck and root:
- crown- this is the visible part that is located above the gum and is directly involved in grinding food;
- neck- this is the part located inside the gum, not covered with enamel, but protected by cement;
- root it is hidden in the alveolus, connecting the teeth with the bone tissue of the jaw, and through which nerves and blood vessels run into the cavity of the tooth.
The cavity itself is filled with soft tissue, penetrated by many nerve and vascular endings, and is called.
The bulk of dental tissue is made up of dentine, which is located around the pulp and is protected from damage tooth enamel on the crown and cement in the region of the neck and root.
Types of teeth
Human teeth differ from each other in their. But, despite this, the anatomical structure of the teeth of the upper and lower jaws is characterized by a similar principle of growth and the same internal structure. In total, an adult should normally have on each jaw.
Each tooth can be seen from six positions. From below, it roots into the gum, on both sides it comes into contact with neighbors (if any), one side is turned to the cheek or lips, the other to the tongue.
Another plane under consideration is the chewing plane. It comes into contact with the same tooth surface of the other jaw every time a person squeezes them.
Inside the tooth contains pulp - a cavity with blood vessels and nerves.
Each tooth in the dentition has its own antagonist. For example, the 6th tooth of the lower jaw, when chewing, is in contact with the 6th tooth of the upper jaw. This allows the food to be ground and prevents the roots from gradually coming out of the alveolus in the absence of pressure on the crown. In addition, it forms the correct bite, which is important for oral health.
The first person to have incisors. They got such a name because with their help the necessary share of food is bitten off (cut) for further processing.
Their shape, resembling a chisel, contributes to this. In incisors, especially the upper ones, the crown is much wider in front and behind than in the side.
As a rule, the roots and root canals of the incisors one at a time. The central incisors are usually larger than the lateral incisors. The crown, however, is not perfectly even, but bumpy, which makes it easier to “saw off” a piece of food of the right size.
The incisors are slightly concave on the inside and rounded on the outside. The roots in this case are quite long and have a conical shape.
Next come. There are only 4 of them - 2 on top and 2 on the bottom. Their roots are also solitary and longer than the coronal part, but not as long as those of the incisors. Unlike incisors, their cutting edge is not as long and can be divided into two halves, distal and mesial, which converge in the form of an angle.
The canine of the upper jaw is wider in crown size than its antagonist on the lower. It is convex on the outside and slightly concave on the inside.
Then come the small molars, or as they are also called -. There are 8 of them in total, that is, on each half of the upper or lower dentition there are 2 pieces - mesial and distal. Roots in premolars, as a rule, from one to two. On the distal, the masticatory surface is sharper, on the mesial, it is flatter and more extended.
In total, an adult has from 28 to 32 teeth
First premolars often look like canines, as they have a sloping outer edge and a pronounced sharp edge. On the lower jaw, the small molars are smaller in size, especially the first ones. The second premolars are more designed for chewing.. They have a larger crown, which often has four sides.
Large molars are also called. Depending on whether the third molars erupted, their number varies from 8 to 12. The coronal part of the molar looks like a cube. However, its edges are not perfectly even. On the chewing surface there are several tubercles that help to effectively grind food in the process of eating.
Large molars usually have three roots on top, while the lower 7th tooth, like the 6th, has no more than two roots. Six, that is, the first of the large indigenous, probably has the largest crown of all teeth especially in the upper jaw. The seven following it is somewhat smaller in size, and it is subjected to less stress during chewing.
third molars
As for the third molars, there are often three to four roots, and they can intertwine into one large cone-shaped root, so even with an x-ray it can be difficult to tell what the roots of the teeth look like in the eighth position.
In some cases, it does not lead to any complications, pain and inflammation. However, sometimes the growth of the eight and its further presence in the mouth causes suffering..
The roots of the tooth contain a root canal through which vessels and nerves pass into the pulp.
In case of such complications, it is necessary to consult a dentist., which, most likely, will send you to take an x-ray and give recommendations on further actions. You may need to cut your gums a little to make it easier for the wisdom tooth to come out. Otherwise, it is likely that it will grow crooked or cause inflammation of the mucous membrane.
In some cases, the third molar will be better removed. Grown incorrectly, in the "backyard" of the jaw, it will be quite difficult to clean, and often the infection that has accumulated on it can cause caries, gum disease, and even an infectious disease. Such a collector of microbes can cause serious damage to the entire oral cavity. and it is not known what diseases can still develop because of this.
Another reason for removal can be the uselessness of the eight in the process of primary food processing. In most cases, the wisdom tooth is not involved in chewing in any way, and if it is clear that it is clearly not healthy, then removal should be started as soon as possible.
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