The arrangement of the upper teeth in humans. Features of the structure of teeth
The dentofacial apparatus of prehistoric and modern humans differs significantly. Ancient people had more than 36 teeth, protruding fangs and a massive jaw. This was explained by the need to chew rough food and raw meat. With the addition of thermally processed foods to the diet, the dentition began to change. The canines were the first to transform, becoming aligned with the bite line. Then the jaw arch narrowed, the interdental spaces disappeared, and the teeth themselves decreased in size. Currently, 32 teeth in humans are the norm, but third molars are considered to be an atavism.
Interesting fact!
The teeth of ancient man cannot be called aesthetic, but they were healthy. According to scientists, cavemen never suffered from caries and other oral diseases.
Name of human teeth
Depending on the location and structure, dental units have their own functional characteristics and are called differently.
- Incisors. On both jaws there are four front teeth in humans - medial and lateral incisors, which are used for biting food.
- Fangs. Sharp teeth designed for chewing hard foods.
- Premolars."Fours" and "fives" on the left and right sides of each jaw arch grind soft or small pieces of food.
- Molars. Three large outer teeth in each row are aimed at grinding coarse substances.
- Fangs and the incisors are included in the anterior group, or “smile zone”, human molars are in the chewing segment.
In addition, teeth are divided into temporary and permanent. In the first case, we are talking about dairy products that appear in children from the fifth month of life to three years. The second refers to the final bite, which is formed in the period from six to thirteen years. Milk teeth differ from permanent teeth only in size, but in structure they are identical.
How many teeth does a person have?
The number of teeth a person has depends on age and anatomical features. The child has a set of 20 primary teeth, which are replaced by a permanent bite of 28 teeth. Third molars erupt, as a rule, after twenty years or do not grow at all, which is not a pathology.
In dentistry, a single numbering of human teeth is adopted. Doctors classify teeth as lower and upper and distinguish the right and left segments of the jaws. Each of them includes two incisors, a canine, two premolars and three molars. The countdown starts from the first front tooth and ends, accordingly, with a figure eight. Sometimes a number is added to the serial number indicating the location zone. For example, the right canine of the top row is numbered 13. This order in the schematic diagram is called the formula of human teeth.
Polyodontia
In rare cases, an anomaly such as polyodontia is observed - supernumerary, or extra teeth in a person. Dental units can appear in the primary and permanent dentition anywhere in the jaw, separate from or fused with the main teeth. The defect affects not only the aesthetics of the smile, but also leads to the formation of incorrect occlusion, impairs the quality of chewing food and diction. Most often, supernumerary teeth are removed in childhood or built into the dentition.
Edentia
There is also a deviation of the opposite meaning called edentia - congenital or acquired absence of dental units. The causes of the phenomenon include heredity or improper development of the embryo in the womb. People without teeth cannot fully eat and speak, have a deformed facial contour and weakened immunity.
Dimensions of human teeth
The upper central incisors are twice as wide as their antagonists. The remaining dental units of the same name have approximately equal parameters. The size is determined using special tables with the optimal size and permissible deviations. Experienced doctors calculate proportions by dividing the length of a person’s teeth by the width. A result of about 0.75 millimeters is considered close to ideal. For more detailed diagnostics, other professional formulas and techniques are used.
Size deviations from the norm occur due to improper formation of the jaw, fusion of tooth buds, or genetic predisposition. Teeth that are too large are called macrodentia, and abnormally small teeth are called microdentia. Pathologies are accompanied by problems with bite and chewing functions, but can be successfully corrected by a dentist.
Interesting fact!
The longest tooth in the world belongs to an Indian teenager. The size of its crown is almost four centimeters. About a year ago, the tooth was removed, and the young man was included in the Guinness Book of Records.
The structure of the human tooth
Anatomy
From an anatomical point of view, a human tooth consists of three parts.
- Crown. The visible part protruding above the gum. It has four sides: the occlusal, or cutting edge, in contact with the antagonist teeth; contact wall adjacent to adjacent dental units; vestibular and lingual surfaces facing the lips and tongue, respectively.
- Root. Fixed in the socket by connective tissue, located in the recess of the jaw. As a rule, premolars have two roots, and molars have three, four or even five. The remaining dental units have one root canal.
- Neck. It is located between the coronal part and the root of a human tooth, surrounded by periodontium.
Histology
What are human teeth made of? Let's look at the cross-section of the structure of a human tooth.
- Enamel. A transparent protective coating of the crown, almost entirely consisting of inorganic microelements.
- Dentine. The hard base of the tooth, containing 80% mineral components and 20% organic substances. The shade of dentin is responsible for the color of dental units, as it shines through the enamel.
- Cement. The bone tissue covering the tooth root. Plays the role of a fastening element connecting the tooth to the alveolus.
- Pulp. Soft tissue filled with bundles of nerves and capillaries. Painful sensations during caries are explained precisely by the presence of nerve endings.
Human wisdom teeth
A “wisdom tooth” is the third outer molar with three to five roots. In structure it is no different from its “neighbors”. To the question “How many wisdom teeth does a person have?” cannot be answered unambiguously. They erupt around the age of twenty, one on each side of both jaws. However, there are people without wisdom teeth. This is a variant of the norm, since in the process of human evolution the need for the “eight” disappeared, and the structure of the jaws underwent corresponding changes. Today, third molars are considered a vestigial organ.
Dental health and human health
The connection between teeth and human organs is not obvious at first glance, but oral health directly affects the functioning of the entire body.
- Gastrointestinal tract. Dental pathologies reduce the quality of chewing food, disrupting digestion.
- Immune system. Oral diseases weaken the overall immune system. As a result, it is difficult for the body to resist bacteria and viruses, which are especially active during epidemics.
- Heart and blood vessels. Inflammation of the tissues of the oral cavity can be accompanied by suppuration, which, in turn, causes intoxication, causing heart failure and angina attacks.
The health of the dentition itself is affected by nutrition, stress, environment and bad habits. The teeth of a smoker, for example, have a yellow coating and are prone to early loss.
Eating sweets provokes the development of caries - the destruction of hard dental tissues, starting with demineralization of the enamel. Poor dental care and untimely treatment contribute to the appearance of inflammatory complications of this disease such as pulpitis, periodontitis or dental cyst.
Healthy human teeth ensure not only the coordinated functioning of the whole organism, but also external attractiveness. A responsible attitude towards oral hygiene, quitting smoking and regular visits to the dentist for preventive examinations will help you maintain a perfect smile for many years.
An important part of the human speech and chewing apparatus are teeth. They take part in breathing and chewing, in the formation of voice and speech. Teeth are incapable of self-healing, and their strength is only apparent. Knowledge of the structure of teeth helps a person to properly care for them and navigate dentists’ recommendations.
In dentistry, doctors use special numbering for diagnosis and ease of filling out patient records.
The order of all teeth is usually written down in the form of a special formula, which is called the dental formula.
In different systems, teeth or groups of teeth that perform the same functions are designated by Roman or Arabic numerals and letters.
There are many systems for naming teeth. These are the standard Zsigmondy-Palmer system, the universal alphanumeric system, the Haderup system, and the international Viola system.
Photo: Designation of teeth according to the Zsigmondy-Palmer system
The Zsigmondy-Palmer system (square-digital) was adopted back in 1876. Its principle is that the teeth of an adult are designated by the usual Arabic numerals from 1 to 8, and in children by Roman numerals from I to V.
In the Haderup system, Arabic numerals are used to designate teeth, in the bottom row with a “-” sign, and in the top row with a “+” sign. Milk teeth are designated by numbers from 1 to 5 with the addition of “0” and the signs “-” and “+” by analogy with permanent teeth.
The universal alphanumeric system adopted by the ADA - the American Dental Association, is distinguished by the fact that each tooth in the dentition has its own number (in adults) or letter (in children).
The count starts from the top right tooth to the left, and then in the bottom row from left to right.
Another dental formula may look like this:
- where M are molars, there are 3 of them in the dentition at the top and bottom on both sides, 12 in total;
- P are premolars, there are 2 of them, 8 in total;
- C - fangs, 1 each, 4 in total;
- I - incisors, 2 each, 8 in total.
We do a simple mathematical calculation and get 32 teeth, 8 in each of the 4 segments.
In 1971, the two-digit Viola system was adopted by the International Dental Federation. According to this system, the upper and lower jaws are divided into 4 quadrants (each into two) with 8 teeth. For adults these are 1, 2, 3 and 4 quadrants, and for children 5, 6, 7 and 8.
The quadrant number is indicated by the first digit, and the tooth number (from 1 to 8) is indicated by the second digit.
This system is the most convenient to use due to the absence of lines and letters. Therefore, in the dentist’s office you can hear that you need to treat tooth 33 or 48, and the child is 52 or 85, for example, this does not mean at all that you have 48 of them, and the child has 85.
Photo: Designation of teeth according to the Viola system
Dental crowns in the jaw form a slender dentition. There are upper and lower dentitions. Each of these rows normally contains 16 teeth. The human dentition is symmetrical; it is divided into right and left halves. Teeth that perform the same functions are designated by the same serial number.
Lower jaw
On the lower jaw, the teeth are designated 4 (right) and 3 tens (left).
- 41 and 31 - front lower incisors, they are also called central or medial;
- 42 and 32 - lateral (lateral) lower incisors;
- 43 and 33 - lower canines;
- 44, 45, 34 and 35 - lower premolars or small chewing teeth;
- 46, 47, 48, 36, 37 and 38 - lower molars or large chewing teeth.
Upper jaw
On the upper jaw, the teeth on the right are marked with the first ten, and on the left - with the second.
- 11 and 21 - front upper incisors
- 12 and 22 - upper lateral incisors;
- 13 and 23 - upper canines;
- 14, 15, 24 and 25 - upper premolars or small chewing teeth;
- 16, 17, 18, 26, 27 and 28 are the upper molars or large chewing teeth.
Internal structure of the tooth
Depending on the function they perform, teeth have different shapes, but they are all similar in structure.
The top of each tooth is covered with enamel. It is the strongest and hardest tissue in the human body. In terms of strength, it is practically not inferior to diamond, since more than 96% consists of mineral calcium salts.
The enamel is formed by prisms and interprismatic substance. On the outside, it is covered with a durable thin shell - the cuticle, which wears off over time on the chewing surface of the teeth.
Beneath the enamel is dentin. It forms the basis of the tooth. This is highly mineralized bone tissue. It is highly durable and second only to enamel in this regard.
Dentin surrounds the tooth cavity and root canal. From the central tissues of the tooth to the enamel, dentin is penetrated by microscopic tubules through which metabolic processes and transmission of nerve impulses are carried out.
Photo: 1 - mantle dentin; 2 - peripulpar dentin; 3 - predentin; 4 - odontoblasts; 5 - dentinal tubules
In the root area, the dentin of the tooth is covered with cement, permeated with collagen fibers. The fibers of the ligamentous apparatus - the periodontium - are attached to the cement.
The internal cavity is filled with loose soft tissue - dental pulp. It is located in the crown of the tooth and in the root. It contains many blood and lymphatic vessels and nerves.
The pulp performs very important functions: tooth nutrition and metabolism. After removal of the pulp, metabolic processes stop.
This is the histological structure of the tooth, and the anatomical diagram of the structure of human teeth shows us that they consist of a neck, crown and root.
Crown
The crown is the part of the tooth that protrudes above the gum.
Dental crowns have several different surfaces:
- the surface of contact with a similar or paired tooth on the opposite jaw is called occlusion,
- the facial or vestibular surface faces the cheek or lips,
- the lingual or lingual surface faces the oral cavity,
- The proximal or contact surface is the side facing the other adjacent teeth.
Neck
The neck of the tooth connects the crown and root.
This is the slightly narrowed part of the tooth. Around the neck of the tooth, connective tissue fibers are located horizontally, forming the circular ligament of this tooth.
Root
The root is located in a small depression - the dental alveolus.
The root ends at the apex, on which there is a small hole. It is through this hole that the vessels supplying the tooth and nerves pass. A tooth can have several roots in total.
The incisors, premolars of the lower jaw and canines have one each. The molars of the lower and premolars (small molars) of the upper jaw have 2 of them. And the molars (large molars) of the upper dentition have 3. In some cases, a tooth may even have 4 or 5 teeth. The longest root is at the fangs.
The root and neck of the tooth with the jaw (the bony surface of the alveoli) are connected by connective tissue fibers that act as a ligamentous apparatus. This is why the tooth is so securely fixed in the alveolus.
And the space between the surface of the alveoli and the root of the tooth, called the periodontium, is separated from the oral cavity by the circular ligament of the tooth.
Video: structure of a human tooth
Both histologically and anatomically, baby teeth are very similar to permanent teeth.
But there are still some differences.
- Primary teeth have a smaller crown size.
- The thickness of enamel and dentin in baby teeth is much less.
- The enamel of a baby tooth is less mineralized.
- The volume of pulp and root canal in baby teeth is larger than in permanent teeth.
Different types of teeth
We bite off food with our front teeth - the incisors. For convenience, they have a flat shape and sharp edges. The canines help tear off pieces of food and separate them.
Chewing teeth are necessary for chewing food. For this purpose, premolars (small chewing teeth) have 2 tubercles, and large ones have 4.
Sixes, or teeth No. 16, 26, 36 and 46, play an important role in closing the jaws, since they rest against each other and are limiters. As a result, they are under enormous pressure. Eights are also simply called wisdom teeth.
Incisors, or front teeth
As mentioned above, a person normally has 8 incisors.
The two central incisors of the upper jaw are noticeably larger than the lateral ones, and on the lower jaw, on the contrary, the lateral ones are larger than the central ones.
The maxillary central incisor is the largest and has a chisel-shaped crown and a single cone-shaped root. Its cutting edge initially has 3 tubercles, which wear off over time.
The lateral incisors of the upper jaw are very similar in shape to the central ones, but smaller in size. The smallest incisors are the central (first) incisors of the mandible. The root is thin and slightly shorter than that of the lateral (second) incisors of the lower jaw.
Fangs
There are 2 fangs on the upper and lower jaws.
The canines of the upper dentition are located immediately behind the second incisors. Together they form a dental arch, in the corner of which a transition from cutting to chewing teeth is formed.
The shape of the canine crown is cone-shaped. The cone tapers towards the cutting edge with one pointed tubercle. The canines of the lower jaw are similar in shape to the maxillary canines, but smaller and shorter.
Molars are divided into small and large, or they are also called premolars and molars.
In the human dentition there are 8 premolars - small molars, 4 on each jaw, 2 on each side.
Premolars are present in the permanent dentition, and they erupt in place of the fallen primary molars. Their main function is to crush food and crush it.
In their structure, they combine the features of molars and canines. They have a rectangular shape, on the chewing surface there are 2 tubercles and a fissure (groove) between them.
The premolars of the upper jaw are similar in shape, but the second premolar is smaller and has one root, and the first has two. The premolars of the lower jaw have a rounded shape. The second premolar is slightly larger than the first. Each has one root.
Molars are located behind the second premolars.
There are 12 of them in total, 3 teeth on each of the two sides on the lower and upper jaw.
The first molars are the largest. The first and second large chewing teeth - the molars of the upper jaw - each have three roots. The first molars of the lower dentition are the largest teeth. The first and second molars of the lower jaw have 2 roots.
Structure of a wisdom tooth
The third molars of both the upper and lower jaws are very diverse in shape and the number of roots can vary. They are often called wisdom teeth.
The timing of wisdom teeth eruption varies from person to person. In some, they erupt very early, and due to various defects they have to be removed. For others, wisdom teeth erupt later.
There are times when they don't come out at all. This is due to the fact that the human jaw continues to undergo changes, since the quality of food has improved significantly, and there is no need to have a powerful chewing apparatus.
Photo
It is much easier to understand the structure of a tooth if you see it in a photo or detailed drawing.
The part of the tooth coming out of the gum - the crown - can tell us a lot about the function of a given tooth. If it is flat, it is an incisor, sharp, it is a canine, wide and rounded or rectangular, it is a chewing premolar or molar.
With age, the composition of teeth and their structure undergo various changes. Since the human dental apparatus takes part in various physiological processes, its condition and health are very important for everyone.
Knowledge of the structure of teeth and their anatomical features helps us to properly care for them. Many people, thanks to this knowledge, have managed to overcome their fear of visiting the dentist. After all, most often fear is generated by ignorance.
Healthy teeth are a decoration for a person. A snow-white smile, an even bite and pink gums indicate that a person is in good health and are generally considered a sign of success.
Why did this happen and why are teeth given such attention?
Teeth are special bone formations that carry out the primary mechanical processing of food.
For a long time, people have been accustomed to eating fairly tough food - plant fruits, grains, meat.
Such food requires good effort to process, and therefore healthy teeth have always been an indicator that a person eats well and variedly.
Diagram of the structure of human teeth
The structure of a 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 apparent fundamentality and reliability are very quickly violated by poor care and bad habits.
And if primary, milk teeth are fragile precisely because of their temporary purpose, then molars 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, which 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 baby and molar teeth, it differs only in that baby teeth are usually designated using Latin numerals, and molars - Arabic.
The dental formula for an average adult looks like this: 87654321|12345678.
The numbers indicate teeth - 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 baby teeth, the dental formula looks different, because there are about 20 of them in total.
Usually, baby teeth grow by 2.5-3 years, and by 10-11 they are completely replaced by molars. We figure it out, maybe at different ages.
Not all people can boast of a smile with 32 teeth. The so-called third molars, or wisdom teeth, can grow in adulthood, and not all 4, but may even remain in their infancy for life, and then there will be 28 teeth in the mouth. Read what to do if your wisdom tooth hurts.
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 itself is somewhat beveled on the outside.
Deuce, or lateral incisor, also has the shape of a chisel and has three cusps 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 from the center to the periphery. Often its upper third has a backward deviation. On the side of the tooth cavity there are three pulp horns corresponding to the three tubercles of the outer edge.
Fang- a tooth that has 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 larger area. This tooth has one cusp on the cutting part. It is this that gives the fang a completely recognizable shape. In many people, this shape is very similar to the teeth of predators.
Next on the upper jaw is located first premolar, indicated by the number 4 on the dental formula. It, unlike the canine and incisors, 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. Between the cusps of the tooth there are grooves that are interrupted by enamel ridges, not reaching the edge of the tooth. The root of the first premolar is flattened, but it already has a bifurcated shape and is also divided into a buccal and lingual part.
Second premolar has a similar shape to the previous tooth. It differs from the first premolar in a significantly larger area of the buccal surface of the tooth, as well as in the structure of the root. At the second premolar it is cone-shaped and compressed in the anteroposterior direction.
The largest tooth in the upper jaw is the first molar, or, as it is also called, the large molar. Its crown is rectangular-shaped, and its chewing surface is diamond-shaped. There are as many as four tubercles on it, responsible for chewing food. An N-shaped fissure runs between the tubercles. This tooth has three roots, of which the palatal one is straight and the most powerful, and the two cheek roots are flat and deviated in the anteroposterior direction.
Second molar slightly smaller in size than the first one. It has a cubic shape, and the fissure between its cusps resembles the letter X. The buccal cusps of this tooth are better defined than the lingual ones. But the roots of this tooth have the same shape and properties as those of its predecessor.
Third molar, or wisdom teeth, not everyone grows. In shape and properties it is similar to the second one, the differences exist only in the shape of the root. At the third molar it is often a fused short powerful trunk.
The structure of the teeth of the lower jaw
The names of the teeth in the human lower jaw generally coincide with their antagonists in the upper dentition. But their structure and properties have a number of differences.
The central incisor of the mandible is the smallest tooth. Its labial surface is slightly convex, and its lingual surface is concave. In this case, the marginal ridge is weakly expressed. The three cusps of this tooth are poorly defined, as are the edges. The root is very small and flat.
The lateral incisor is slightly larger than the central incisor, but is still 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. The root is single, flat, and has longitudinal grooves.
The fang of the lower jaw is similar to its upper counterpart. It also has a diamond shape, convex on the tongue side. But, unlike the upper canine, this tooth has a narrower shape. All its faces converge on one central tubercle. The root of the tooth is flat, deviated inward.
The first lower premolar has only two cusps. Its chewing surface is beveled towards the tongue. The shape of this tooth is round. The root of the first premolar is single, flat and slightly flattened laterally. There are grooves along its frontal surface.
The second premolar of the mandible is larger than the first 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 Z. The first molar has two roots. The rear one is slightly shorter than the front one and has only one channel. The anterior root has two canals - anterior cervical and anterior lingual.
The second molar of the mandible is similar to the first with a cubic crown and roots.
The third molar is also similar to them. Its main difference is the variety of tubercles options. There are a huge number of types of their development in this wisdom tooth.
Anatomical structure of the tooth
This concerns the structure of the jaw and individual teeth. But the anatomical structure of the tooth implies the presence of the following parts:
- crowns,
- cervix,
- root
Crown called the part of the tooth that is located above the gum. That is, visible to everyone.
Tooth root located in the alveolus - a depression in the jaw. The number of horses, as becomes obvious 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 a tooth in cross-section, you will notice that it consists of several layers.
The outside of the tooth is covered with the hardest tissue in the human body - enamel. In newly emerging teeth, the top is still covered with a cuticle, which over time is replaced by a membrane derived from saliva - the pellicle.
Histological structure of the tooth
Beneath the enamel is a layer of dentin, the foundation of the tooth. In its cellular structure it is similar to bone tissue, but its properties have a much greater margin of safety due to increased mineralization.
In the area of the root, where there is no enamel, the dentin is covered with a layer of cement and penetrated by collagen fibers, which secure the periodontium.
In the very center of the tooth there is connective tissue - pulp. It is soft, penetrated by many blood vessels and nerve endings. It is its destruction by caries or inflammatory processes that causes that unbearable toothache.
The structure of baby teeth in children
Despite the fact that there are fewer primary teeth than primary teeth, and their structure is different, they are very similar in shape and purpose.
The main difference is that they are almost always smaller in size than their native followers.
The crowns of baby teeth have enamel and dentin with a lower degree of mineralization than molars, and therefore are more susceptible to caries.
At the same time, the pulp in baby teeth occupies a larger volume than in molars, and is also more susceptible to all kinds of inflammation and painful processes.
The tubercles of the cutting and chewing parts are also weakly expressed on their surface.
At the same time, the incisors of baby teeth are more convex than those of permanent teeth, and the tops of their roots are curved towards the labial side.
Also, all baby teeth are distinguished by not too long and strong roots, due to which changing teeth in childhood is not too painful.
All these structural features 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 baby teeth from childhood in order to avoid problems with molars in the future.
Teeth are a very complex system of the human body. They bear a tremendous burden throughout their lives. Moreover, each tooth has its own shape, the most suitable for its purpose, the number of tubercles intended for efficient processing of food, its own root system and their location in the alveolus.
In addition, the internal structure of 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 their apparent strength, teeth are a very fragile system that requires constant care and attention to the processes occurring in them, due at least 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 healthy, strong and beautiful for a long time.
Pictures, photos of the structure of a human tooth:
Tooth anatomy
Is it true that baby teeth don't have roots? What is included in the concept of anatomy of the dental system? What are tooth surfaces? How are dental organs structured, what do they consist of? What are the differences between the lower teeth and their antagonists? What does the clinical anatomy of teeth look like? What is the vestibular surface? Answers to all the reader’s questions about their structure (with visual drawings and detailed descriptions) can be found in this article.
Why do people need teeth?
Human teeth are independent organs. Without teeth, a full life is impossible. The vast majority of people believe that the only purpose of teeth is to help break up pieces of food before they are sent for further processing into the human digestive system. In addition to the chewing function (that is, the mechanical processing of food), human teeth have several other tasks:
- formation of an aesthetic and attractive image;
- participation in the creation of a “framework” for the human face;
- articulation and speech.
The number of teeth a person has and their location on the upper and lower jaw
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The child grows 20 primary teeth – 10 on the bottom and the same number on top. The quantity is determined by the structural features of the jaw. However, by the age of 13–14, temporary units are replaced by permanent ones. Normally, 28 permanent teeth should erupt. At the age of 18-25, some people grow third molars. Each jaw contains 14–16 teeth.
The lower teeth have the same names and functions as their antagonists. They are divided into several varieties, based on the structural features of the human tooth, the functions performed and the dislocation in the row. Formation of the bite, prevention of the gradual exit of the roots from the alveoli and grinding of food become possible due to the fact that each tooth has an antagonist on the opposite jaw.
The main types include:
- Incisors. Front teeth shaped like a chisel. They have 1 root. A pair of central and lateral incisors erupt in each jaw. The structure of the central teeth (incisors) of the human upper jaw is similar to the lateral ones, but the first ones are larger. With teeth in the lower jaw the opposite is true. You can see teeth of this type in the photo accompanying the article.
- Fangs. There are 4 pieces in the dental system. These teeth are characterized by a wedge-shaped shape. Single root. The canine of the upper jaw, like its antagonist from among the lower teeth, has a cutting part, which is divided into mesial and distal halves, which converge at an angle. The canine crown of the upper jaw is larger than that of the “paired” canine in the lower jaw. The maxillary canine, like any third molar, can be impacted, but this is extremely rare.
- Premolars. There are 8 premolars in the dental structure - two pairs in each jaw. They are distinguished into distal (first) with a sharper shape of the chewing surface. Mesial (second) - these teeth have a flattened crown shape. They have 1 – 2 roots. The differences between the first and second pairs of premolar teeth can be seen in the photo.
- Molars. There can be from 2 to 3 pairs in the top and bottom row. They perform a chewing function and are distinguished by the rectangular shape of their teeth. The molars of the dental jaw have three roots on top, two on the bottom, with the exception of the third molars - their number and location of roots is unpredictable. Typically, the maxillary first molars are the largest teeth. The lower teeth are usually smaller in size than the upper teeth, but have the same shape. Photos of molar teeth are also presented above (more details in the article: molars: structural features of teeth).
Anatomical structure of teeth with photos
What is the real structure of a tooth? Many people mistakenly consider it a bone. However, in fact, it is a full-fledged organ of the human dental jaw with its own functions and structure. If you look at any of the bones under a microscope, you can identify a number of differences that prove this statement.
The human dental system begins to form during intrauterine development. There are three main parts of the tooth - roots, neck and crown. When a person smiles, only the crown is visible. The clinical anatomy of teeth in section is presented for visual reference in the photo accompanying the article.
The tooth also has a cavity and surfaces. The surfaces of the tooth and their names are clearly indicated in the diagram accompanying the article. The internal cavity consists of the root canal and the coronal cavity - blood vessels and nerves pass through here. There are five main tooth surfaces on the coronal part:
- The occlusal surface of the tooth is a generalized name for the cutting edges of the canines and incisors and the chewing surfaces of molars and premolars, the surface is directed towards the antagonists.
- Medial approximal - contact surface facing the adjacent unit from the side of the center of the row.
- The distal approximal surface is the same as the medial one. The difference between the distal dental surface is that it faces away from the center of the row of teeth.
- Lingual - the surface facing the inside of the oral cavity, towards the tongue, which explains the name of this surface of the tooth.
- Vestibular - the surface of the tooth that “looks” into the vestibule of the oral cavity; in the back teeth it is also called the vestibular buccal surface, and in the front teeth – the vestibular labial surface (see also: description of the functions of the human oral cavity with photos).
Crown
Depending on the type of tooth, the appearance, shape and size of its crown part may vary. In dentistry, anatomical and clinical crowns are distinguished:
- The first is the part that is covered with a protective layer of enamel. Its dimensions remain unchanged throughout the life of the dental element.
- Protruding above the gum and visible when smiling and talking is called a clinical crown. During eruption or during a recession, its size may change. Plaque accumulates on this part and caries most often develops. In most cases, the disease affects the chewing surface of the tooth.
Tooth neck
The cervix is the least protected part. Normally, it is located inside the gum. The surface of the anatomical neck of the tooth is not covered with either enamel or cement - this area corresponds to the cement-enamel boundary. In the anatomy of human teeth, it represents the area where the crown (anatomical) transitions to the root. The neck of the tooth is characterized by a narrowed shape.
Roots
Histological structure
The histological structure is very reasonable. Due to the structural features of molars, they perform their functions and signal the occurrence of pathological processes, including the development of caries, due to the proliferation of microbes in the nutrient medium of plaque. In the photo accompanying the article you can see the main components of the structure under a microscope. Histological structure of the human tooth:
Pulp and periodontium, tooth root structure
Pulp is the soft, loose tissue within the structure of the tooth. It contains a network of nerve fibers and blood vessels that make up the human tooth. The older a person is, the smaller the volume of the soft part in his teeth, since over time it is replaced by deposits of secondary dentin. The main functions of the pulp include responding to irritants, forming and nourishing dentin tissue.
The composition of the periodontium (or pericement, as it is called in some sources) includes a system of nerve fibers and blood vessels, collagen fibers. This connective tissue fills the space between the alveolus (wall) and the root cementum. The periodontium is designed to perform the following functions:
- stimulation of metabolic processes in periodontal tissues;
- transmission of chewing pressure to the walls of the socket;
- perception and absorption of loads arising from chewing food.
Features of the structure of baby teeth in a child
A child's baby teeth constitute a temporary bite. In their structure and form they are similar to the indigenous ones. They also have a crown part, a neck and roots. However, the anatomy of primary teeth has its own characteristic features.
Many people believe that baby teeth are completely devoid of roots or have only weak thin roots. In fact, temporary roots are very similar in shape to permanent roots, but are smaller in size. Approximately 1.5 - 2 years before the loss of a baby tooth, its root begins to dissolve, so by the time the bite changes it is difficult to detect it. The shape of a baby tooth can be seen in the figure.
Another feature of baby teeth is thin enamel and a small layer of dentin. This is explained primarily by the size of temporary dental elements, as well as the short “planned” service life. The main disadvantage of this feature is that, due to the thin protective layer, children's teeth are susceptible to the influence of pathogenic microbes that provoke caries, which quickly progresses to the stage of pulpitis.
And finally, a selection of interesting facts about human teeth. It’s worth starting with the fact that teeth contain almost all the calcium that can be found in the body - they get up to 99% of this substance, while the rest of the skeleton has to be content with “pathetic” remains. Most of the calcium is concentrated in the enamel, which protects the inner layers of the tooth from the penetration of microbes.
Below is a selection of the most interesting information about teeth:
- to get rid of bleeding gums, it is enough to eat two grapefruits a day, the diet will not only relieve inflammation, but also normalize metabolism and promote weight loss - however, it will not be a bad idea to undergo a professional cleaning procedure to get rid of plaque;
- the most dangerous sport for a smile is ice hockey;
- in rare cases, a child may be born with one or two teeth; such amazing babies included Gaius Julius Caesar;
- The famous Greek physician Hippocrates began to call temporary teeth in children “milk”; he thought that these dental elements are formed from mother’s milk;
- if you pay attention to the images of the teeth of our ancestors, you will find that there were not 32, but 44 of them;
- scientists have proven that teeth are directly related to memories, and when losing one of these organs for some reason, a person loses part of his memories.
Healthy and beautiful teeth are a decoration for any person. Pink gums, an even bite and a snow-white smile indicate that a person has excellent health and, in general, is considered a sign of success. Why is so much attention paid to teeth and why did this happen?
General concepts about teeth and their classification
Teeth are special bone formations that carry out the primary mechanical processing of food. People have long been accustomed to eating rather tough foods - meat, grains, plant fruits. This food requires considerable effort to process, and therefore healthy teeth have always been considered an indicator that a person eats a varied and good diet.
To begin with, what you need to know about teeth is the only organs in the human body that cannot be restored. Both their apparent reliability and fundamental nature are quickly violated by bad habits and poor care.
And if milk, primary teeth are fragile precisely because of their temporary purpose, then the molars are given to a person for the rest of his life. In general, the entire dentition in a person is divided into the following types:
- fangs;
- incisors (lateral and central, also called lateral and medial);
- molars or large molars (this also includes the upper and lower wisdom teeth that grow in a person in adulthood or young age);
- premolars or small molars.
As a rule, the location of the dentition on the upper and lower jaw is recorded using the so-called dental formula. For molars and milk teeth, this formula differs only in that the molars are most often designated using Arabic numerals, and the milk teeth - in Latin.
For an average adult, the dental formula looks something like this: 87654321|12345678. The numbers indicate teeth - any healthy person must have one canine, 2 incisors, 3 molars on each side, 2 premolars on the upper and lower jaw. As a result the total quantity is 32 pieces.
For babies who have not yet had their primary teeth replaced, this formula looks different, since there can be as many teeth as approximately 20 pieces. As a rule, temporary teeth erupt by 2–3 years of age, and by 9–12 years they are completely replaced by permanent teeth. However, not all people can boast of having all 32 sprouted teeth.
Since wisdom teeth or third molars can appear in adulthood, or they can remain completely in their infancy all their lives, and in this case in a person’s oral cavity there will be 28 teeth. Moreover, the structure of the lower and upper jaws has certain differences.
Anatomical structure
The anatomy of a human tooth suggests that it is conventionally divided into 3 parts: root, neck and crown. The crown is the part that rises above the gum; it is covered with enamel - the strongest tissue that protects the tooth bone from the negative effects of acids and bacteria. There are several types of crown surfaces:
The neck is the part that is between root and crown, connecting them, covered with cement and closed by the edges of the gums. The root is the part with which the tooth is attached to its socket. Taking into account the classification type, the root can have 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 they perform.
Enamel. This durable fabric, which consists of 95% of various salts such as zinc, magnesium, copper, strontium, fluorine and iron. And 5% consists of substances such as carbohydrates, lipids, proteins. In addition, the enamel contains a liquid that participates 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 wear off and become thinner.
The basis of the bone tissue of the tooth is dentin is a collection of minerals surrounding the root canal and the entire dental cavity. Dentin tissue contains a large number of tiny channels through which metabolic processes take place and nerve impulses are also transmitted through the channels.
Root structure: pulp and periodontium
The cavity inside the tooth is formed by the pulp - this is a loose and soft tissue, penetrated through and through by nerve endings, as well as lymphatic and blood vessels.
The structure of the roots looks like this. The root is in a special hole - the alveolus, in the bone tissue of the jaw. The root, like the crown, consists of mineral tissue - dentin, covered on the outside with cement.
Root ends with apex, through its opening pass blood vessels that feed the dental bone. 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 teeth.
Periodontium is connective tissue, which fills the gap between the jaw socket and the tooth root. The fibers of the 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 this the tooth is firmly attached. In addition, through the periodontal tissue, the feeding elements of the blood vessels can enter the dental tissue.
Description of the dentition
Incisor teeth. The human jaw is symmetrical and contains the same number of teeth of each type. But there are certain anatomical features of the upper and lower jaw. Let's look at them in more detail.
Incisors are the front teeth. A person has eight of them - 4 at the bottom and 4 at the top. Incisors are needed to bite food and separate it into parts. The peculiarity of the structure of the incisors is that they have a flat, chisel-shaped crown with rather sharp edges.
On anatomical sections there are three tubercles, which are erased throughout life. On the jaw from above two central incisors– in its group the largest of all incisors. The lateral incisors are similar in shape to the central ones, but smaller in size.
What is noteworthy is that the immediate cutting edge of the lateral incisor also has three tubercles, and often takes on a convex shape as a result of the development of the central tubercle. The root of the incisor takes the shape of a cone, and is flat and single. A distinctive feature of the incisor is that on the side of the tooth cavity there are three pulp tips, corresponding to the tubercles of the cutting edge.
The anatomy of the upper teeth is slightly different from the structure of the lower dentition, so in the lower jaw everything is exactly the opposite. Middle incisors are 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 surface is concave.
Incisor crown, side view curved towards the lips and very narrow. The cutting edge has 2 angles - in the center, more acute, and inside - more obtuse. The roots have longitudinal grooves.
Chewing teeth and fangs
Fangs are used to break down food into smaller pieces. The anatomy of the fangs 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 fangs has one pronounced and developed tubercle, this makes the cone-shaped crown often similar to the fangs 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, inclined inward and the longest, unlike the roots of other teeth. In humans 2 fangs on both jaws. The lateral incisors with the canines form an arch, where the transition from the incisors to the chewing teeth begins in the corner.
Let us consider the structure of the small chewing tooth first, and then the large chewing tooth. Their main task is careful processing of food. This function is performed by molars and premolars.
Premolars
The first premolar (No. 4 in the dental formula) differs from the incisors and canines in its prismatic shape, and there are convex surfaces on the crown. The surface has 2 tubercles - lingual and buccal, with grooves between them.
The buccal tubercle is much larger in size than the lingual one. The root of the first premolar has flat shape, but with a slight bifurcation into the lingual and buccal parts.
The second premolar is similar in 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 towards the tongue.
The second premolar is larger than the first due to the fact that both tubercles are symmetrical and equally developed, and the depressions in the enamel between them have the shape of a horseshoe. The root is the same as that of the first premolar. In a person's 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 is similar to a rectangle, and the chewing surface is diamond-shaped with 4 tubercles. This molar has three roots: one straight - the most powerful, and two buccal - flat, deflected in the posterior direction.
When the jaws close, the first molars rest against each other and form a kind of “limiter”“, because of this, they undergo significant stress throughout a person’s life.
Second molar has smaller dimensions. The roots are the same as those of 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 cusps. This molar two roots– front with two channels, rear – with one. In this case, the anterior root is larger than the posterior one. In the lower jaw, the second molar is similar in structure to the first. The number of molars in humans is the same as the number of premolars.
The third molar is called " wisdom tooth“, and in total a person has four of them in the dentition, two on each jaw. On the jaw below, the third molar has many variations in cusp development. As a rule, there are five of them. And, in general, the structure of a person’s “wisdom tooth” is the same as the structure of the second molar, but the root usually resembles a very powerful and short trunk.
Baby teeth
The histological and anatomical structure of a baby tooth is similar to the structure of a molar tooth, however, there are certain differences:
In the end, I would like to note that, naturally, the arrangement of teeth in the jaw, their structure, closure have an individual character for each specific person. But the dental apparatus of each person performs vital functions throughout life, therefore, over time, the dental structure changes.
We must not forget that in dentistry, many pathological processes appear in childhood, so you need to monitor the condition of your teeth from childhood. This will help avoid problems in the future.
Despite their apparent simplicity, teeth are quite fragile and complex system, with a multilayer structure, where each layer and element has its own specific purpose, as well as certain properties. And the fact that teeth change only once during a lifetime makes the structure of the human jaw different from the anatomy of the jaw of other representatives of the fauna.
