Human teeth - structure, quantity, numbering and composition

Teeth of ancient people

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.

When do baby teeth appear?

The formation of a child’s teeth begins in the womb: this is partly why doctors recommend that pregnant women eat foods rich in calcium and other beneficial minerals. After birth, the first baby tooth (in the vast majority of cases, this is the lower incisor) appears when the baby is six months old. There are cases when the first teeth erupt already in the third month, and sometimes a child is already born with one or more teeth (among many peoples this is considered a lucky sign). Conversely, some children acquire their first teeth after reaching one year of age. Below you can see a table that shows the current timing of the appearance of baby teeth.

Milk teeth on the lower jaw

Milk teeth on the upper jaw

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.
• The canines
  and incisors are part of the anterior group, or the “smile zone,” and the human molars are part of 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 between six and thirteen years of age. Milk teeth differ from permanent teeth only in size, but in structure they are identical.

Prosthetics of frontal units

Prosthetics of anterior teeth is a complex process from a technical point of view. It requires the doctor to take special care in carrying out each manipulation, since as a result the patient hopes to receive an exact copy of a healthy tooth with the appropriate shape, shade and strength. Progressive prosthetic methods allow you to achieve ideal results

in recreating the integrity and beauty of the frontal zone.

For high-quality restoration of segments in the smile area, three crown options are used, which are the most acceptable, both in terms of strength and aesthetics, for replacing natural segments:

• Zirconium.
• Ceramic.
• Metal-ceramic.

If it is necessary to install dentures on the front teeth, crowns made with ceramic or zirconium are first considered. The fastest and most promising option is an orthopedic crown on a tooth using CEREC technology. You can get an attractive smile in just one visit. However, it is also the most expensive. A compromise in this case could be a metal-ceramic prosthesis.

A turnkey metal-ceramic tooth crown is an excellent combination of price, quality and aesthetics. The only drawback is the metal base; it can be visible through the ceramics. But the defect is noticeable if the crown is on only one segment. If you plan to install a crown on four or six front teeth

, it will be difficult to distinguish natural teeth from dentures.

Today, very often, patients no longer choose metal-ceramics, but e-max or cerec ceramics, which not only do not have the disadvantages of metal-ceramic crowns, but also look aesthetically more beautiful.

Classic dental prosthetics, regardless of the location of the crown, is carried out in stages.

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 representation 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.

Aesthetic rehabilitation of anterior teeth using direct composite restorations

D. Volkov

specialist in the field of endodontics, member of the RSO, participant in international congresses VDW Endodontic Synergy

K. N. Khabiev

Ph.D., specialist in aesthetic rehabilitation, group president

Harmony and naturalness of a smile are important factors for the successful social integration of a modern person, the key to his inner confidence when communicating with others. Increasingly, the dentist has to solve not only medical problems related to the prevention and treatment of various specialized diseases, but also eliminate the aesthetic problems of the patient’s smile.

The most popular method of restoring teeth is direct composite restoration. With its help, you can not only restore the volume of tissue lost due to a pathological process, but also correct the anatomical shape of the teeth to harmonize the patient’s smile ensemble. To successfully implement a rehabilitation plan using direct composite restorations, a material is required that meets many requirements, such as high mechanical strength and resistance to abrasive wear, optical characteristics characteristic of natural tissues, good polishability and durability of the “dry shine” of the surface over time. In this article, we will consider the nanofilled restoration composite CAPONatural (SchützDentalGmbH) as the material of choice.

The reasons for the choice are the flagship strength properties (Young's modulus - 11173 MPa; Vickers hardness 784 MPa; compression load 502 MPa), refractive index -1.62, corresponding to the natural refraction of enamel, a wide palette of colors adapted to the stratified tooth restoration technique. The low volumetric shrinkage rate (1.2%) due to the high filling of the polymer matrix makes it possible to significantly simplify handling techniques for introducing and distributing portions of the material.

Restoration requires a material that meets many requirements, such as strength and wear resistance, and optical characteristics characteristic of natural tissues. Using only three layers of material, you can achieve a full match of the color of the restoration to the color of the tooth being restored. The main task of a restorative dentist is to achieve equal transparency of the tooth being restored and the restoration. The first layer of dentin should be two shades darker than the base color. If the main color is A3, the first shade should be A4. We use it to restore 70-80 percent of the tooth. Then the main dentin shade is applied (up to 90% of the restoration). The remaining 0.3-0.5 mm are restored using an enamel shade according to Table No. 1.

Table No. 1

Tooth color according to Vita Dentin 1 Dentin 2 Enamel A1 A3 A1 Incisal white A2 A3.5 A2 Incisal medium A3 A4 A3 Incisal medium A3.5 A4 A3.5 Incisal clear A4 A4 A4 Incisal clear B1 A2 A1 Incisal white B2 A3.5 B2 Incisal medium B3 A4 B3 Incisal clear C2 A3.5 C2 Incisal clear C3 A4 C3 Incisal clear

Shades for creating a snow-white smile light Primary tooth color Bleach 1 Incisal white extralight Primary tooth color Bleach 2 Incisal white

Clinical case

Initial situation: the existing composite restorations, made about 5 years ago using the direct method, are aesthetically untenable: teeth 11 and 12 have a pronounced discoloration, teeth 11 and 23 show marginal depressurization and staining of the fillings. The surfaces of all restorations do not have a “dry shine” and are visually defined as matte.

On the palatal surface of teeth 12, 11, 21, 22, 23, marginal depressurization and staining of fillings and secondary caries are observed. There is deep caries on the proximal surfaces of teeth 13 and 12 (Fig. 1-3).

Rice. 1. Initial situation. Rice. 2. Initial situation from the palatal surface. Rice. 3. The patient’s smile before treatment.

After making the silicone key, the old restorations were removed; after removing the material, strong gray-brown pigmentation of the dentin of tooth 12 was observed. Additional translucent optical diagnostics were carried out to determine the contours of the dentinal body (Fig. 4-5).

Rice. 4. Making a silicone key. Rice. 5. View after removal of old restorations.

A layer of transparent enamel (incisal medium) is applied to the silicone key (Fig. 6). The palatal surfaces of the teeth were restored using a silicone key with an incisal medium enamel shade (Fig. 7-8).

Rice. 6. Applying a layer of transparent enamel (incisal medium) to the silicone key. Rice. 7. Restoration of the palatal surface using a silicone key. Rice. 8. The palatal surface was restored with incisal medium enamel shade.

Restoration of contact points using a transparent matrix and wedge (Fig. 9). The cervical area of ​​the teeth was restored with Capo Slow flow composite material, color A4 (Fig. 10).

Rice. 9. Restoration of contact points using a transparent matrix and wedge. Rice. 10. Restoration of the cervical area with flowing composite material Capo Slow flow (A4).

Restoration of 70-80% of the tooth with a dark dentin shade (A4) (Fig. 11). Applying a shade of the main color (A3) and forming mamellons (A1) (Fig. 12) and the enamel layer (incisal medium) (Fig. 13).

Rice. 11. Restoration of 70-80% of the tooth with a dark dentin shade (A4). Rice. 12. Applying a shade of the main color (A3) and forming mamellons (A1). Rice. 13. Applying an enamel layer (incisal medium).

The final appearance of the restoration after polishing with PoGo heads (Dentsply) and DialogGlass micron paste (SchützDentalGmbH) based on aluminum oxide. Enhance polish cup (Dentsply) polishing sponges were used as a carrier (Fig. 14).

Rice. 14. Final view of the restoration after polishing with PoGo heads.

In Fig. 15-16 shows the view of the restoration the next day, in Fig. 17-18 - 5 years after the start of treatment.

Rice. 15. View of the restorations the next day. Rice. 16. View of restorations from the palatal side. Rice. 17. View of restorations after 5 years. Rice. 18. The patient’s smile 5 years after the start of treatment.

Using only 3 layers of material, you can achieve a full match of the color of the restoration to the color of the tooth. The main task is to achieve equal transparency.

Analyzing this clinical case, we can confidently state that a nanofilled restoration composite material, which has high physical and mechanical characteristics and optical parameters similar to natural tissues, can be successfully used not only for local aesthetic restoration of a specific tooth, but also for complex artistic rehabilitation of the patient’s smile as a whole.

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.

Dental clinic No. 2

The anterior teeth of the upper jaw are characterized by both functional and aesthetic parameters.

By their nature, these are the teeth that are visible both when talking and when smiling. That is why there are such a significant number of approaches trying to imitate as much as possible all the subtleties of the anatomy of the teeth of the upper jaw. Considering that in addition to shape, the technician must also understand the characteristics of color, texture, rotation and spatial position of the teeth, it is quite easy for him to get lost in all these details. That is why in this article we will focus not on individual modeling elements, but on a systematic approach to restoring the morphology and structure of the frontal group of teeth.

After completing the modeling of the basic shape, the technician can begin to restore the individual characteristics of the tooth, following the proposed protocol, thereby saving a huge amount of time.

The described approach is unique in both modeling all six anterior units and restoring the shape of a single tooth, regardless of whether the technician is working with wax or final structures, in conventional or digital mode. After all, the most important thing lies in the details, which are emphasized after modeling the basic form of future restorations.

Step by step protocol

1. When restoring several anterior teeth, modeling should always begin from the middle of the row, namely from the labial cutting edge of the central incisors. The middle of the restoration is determined by the median anatomical landmarks of the face: along the line connecting the bridge of the nose, the apex of the nose and the center of the chin. The second interpupillary line (photo 1) is modeled perpendicular to the midline of the face: the cutting edges of the incisors on the labial side should be parallel to the interpupillary line.

Photo 1. Facial landmarks and transfer of the interpupillary line to the horizontal plane of the central incisors.

2. After this, contact points are modeled: the position of those from the incisors to the canines shifts more and more towards the cervical area, as shown in the photo with a red line (photo 2 - 3).

Photo 2. The area of ​​contact points shifts more cervically from the incisors to the canines.

Photo 3. The area of ​​contact points moves more cervically from the incisors to the canines (red lines).

3. At the next stage, the lingual surfaces are modeled. Since all teeth take part in the act of chewing, it is therefore simply impossible to model their lingual surface without taking into account the interaction with antagonist teeth. The cutting edge of the teeth, in essence, is their cutting ridge; in the photo, the line of the cutting edge on the labial side is shown in red, and on the lingual side - blue (photos 4 - 5). These edges are the boundaries of the cutting ridge. We should not forget that the lingual edge of this ridge is not only an aesthetic, but also a functional component that interacts with the lower incisors during chewing, while the labial edge of the upper teeth is visualized when the patient smiles and talks. The labial margin of the restoration can be lengthened or repositioned as long as it does not compromise the function, esthetics and phonetics of the teeth being modeled. The cutting edges are rarely symmetrical and parallel (photos 4 - 5). Simply put, the function of the lingual side of the incisors is derived from their labial contour.

Figure 4. The incisal ridge consists of a labial edge (red line) and a lingual edge (blue line).

Figure 5. The incisal ridge consists of a labial edge (red line) and a lingual edge (blue line).

4. The mesial angle line, which is represented in the photo by a black line, is the next element for modeling (photo 6). If you look at the teeth from the front side, they can be divided into segments vertically (photo 3): the central one can be divided into three parts, the lateral incisors and canines into two. The line of the mesial angle of the central incisor begins near its contact point and ends in the cervical part of the tooth in the region of the mesial third of its lateral side. The line of this angle should correspond as much as possible to the line of the adjacent central incisor. A similar lateral landmark for the lateral incisor begins at or above the contact point and ends in the cervical region near the middle of the tooth side. The line of the mesial angle of the canines also begins above the contact point and moves towards the middle of the tooth.

Photo 6. Mesial angle line (black line).

5. After this, they begin to model the lines of the distal angles (photo 7), again moving from the area of ​​the central incisors to the canines. These landmarks should coincide as much as possible between the teeth on the right and left sides. Of course, the width of a symmetrical tooth may differ, but they can be optically modified to ensure that the lines of the distal angles coincide as much as possible.

Photo 7. The distal angle line moves from the incisors to the canines.

6. The height of the cervical contour, drawn with a white line (photos 8 - 9), should follow the contour of the soft tissues (pink) as much as possible. Therefore, when modeling this parameter, it is necessary to use a duplicate of the soft tissue position. The apex of the cemento-enamel junction of the central incisor is located in the area of ​​the distal third, and the lateral incisor and canine are in the area of ​​the middle of the tooth (photo 6).

Photo 8. The height of the cervical contour (white line) follows the contour of the soft tissues.

Photo 9. The height of the cervical contour (white line) follows the contour of the soft tissues.

7. The last step in modeling is to adjust the labial component of the incisal edge. The shape of this formation (photo 10) can vary greatly, since it does not interact with the cutting edges of the lower incisors during chewing.

Photo 10. Shape of the labial edge.

Typically, the labial edges of the central incisors and canines follow a horizontal line, but during modeling the author uses a Kois Waxing Guide (Panadent) (Figure 11) to ensure that the incisors and canines are exactly in the same horizontal plane.

Photo 11: Kois Waxing Guide is used to check the horizontal plane of the incisors and canines.

If you outline the main forms of modeling without teeth, then everything becomes simple and clear (photo 12). It is important to correctly fill in these lines during restoration and connect the corresponding points correctly. After rough modeling, the technician begins to restore individual parameters. With the vestibular view of the teeth, the distal side of the canines disappears from the field of view or is very faintly traced (photo 13), so the visual shape of the dental arch can be expanded due to better visualization of the distal side of the third teeth.

Photo 12. View of the base lines without teeth.

Photo 13. In the vestibular view, the distal part of the canines is faintly visible.

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.

Two methods of prosthetics for front teeth for caries:

1. The crown on the front teeth is attached to a pin

– a miniature screw rod is screwed into the sealed root canal. Filling material is applied to its upper part, ground to the required size, and a crown is installed. But again, pins are gradually being replaced by the more patient-friendly CEREC technology. And patients come to me with problems with previously installed pins with the goal of replacing them with a single dental module, as in the following video:

2. Crown on the front tooth using a stump inlay

– this element is made in the laboratory. Outwardly, it resembles a tooth stump. It is securely attached to the root canal and the prosthesis is securely fixed on its upper part (stump). But, despite its popularity, the stump inlay has one significant drawback - it forms an additional adhesive connection both with the tooth tissue and with the crown being installed. This can be avoided by restoring the front teeth using CEREC technology. When using Cerec technology and using “root + crown” type modules, we reduce the gluing points to just one:

Installation of dentures using “root + crown” modules on the front teeth increases the service life of the crowns. In addition, they allow you to create the ideal tooth shape, which is important when replacing teeth in the smile area.

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.

Milk teeth in adults: when childhood drags on

Yes, this happens, but very rarely. In dentistry, there are cases where baby teeth were found in thirty-year-old and even fifty-year-old people: doctors call such teeth persistent. What is the reason for such dental infantilism? This happens precisely for the reason that we talked about above. When a person lacks the rudiments of permanent teeth, the replacement mechanism does not start. Simply put, nothing puts pressure on the roots of baby teeth, which is why they do not dissolve, but remain in the oral cavity of an adult. It also happens that the rudiments of the molars are located too deep and also do not come into contact with the roots of the milk teeth. Treatment here is purely individual. If a person has a healthy baby tooth with intact roots, under which there is no molar rudiment, it makes sense to have it replaced with a veneer or crown in order to protect it from the external environment and give it the desired shape. If the baby tooth is unstable and its roots are resorbed, extraction is recommended. If there is a permanent tooth germ underneath, then it is “pulled” out; if not, a prosthesis is installed.

Tooth development.

The formation of the rudiments of baby teeth in the fetus begins at 4–5 months of intrauterine development. That is why the mother’s illnesses during this period lead to disruption of various stages of dental development, for example, a violation of the mineralization of the tooth occurs. As a result, the enamel can become weak and brittle. Taking certain medications during this period can also affect the development of teeth. For example, if the mother was treated with tetracycline antibiotics, the child’s teeth will be dark yellow or even brown (so-called tetracycline teeth).

Enamel mineralization begins in the prenatal period and continues for 6 months after birth. Mineralization of the crown part of the teeth has time to take place in utero, while mineralization of the cervical region of the incisors, canines and molars continues after birth, in completely new and not always favorable conditions. The mineralization process can be negatively affected by the nature and diet, social living conditions and various diseases of the child (acute respiratory infections, intestinal infections and functional diseases). That is why the cervical area is the most vulnerable and typical place for the occurrence of “bottle” caries of primary teeth.

What are the anatomical features of “children’s” molars?

• The first upper molars are smaller in size than the second ones. The first has two widely spaced roots, which sometimes merge to the apex. The rudiment of the first “adult” premolar is formed between the roots. Most often, the first upper molars have four root canals, although there are also three or two (in 19 and 5% of cases, respectively).
• The first lower molars differ from others by having an elongated prismatic crown. On their chewing surface there are four tubercles: lingual, higher, and buccal. The first “children’s” molar has 2 roots, with the medial one being longer and wider than the distal one. Often the first lower molars have three canals.
• The structure of the crown of the second upper molars of the dentition resembles the first upper permanent tooth. Four tubercles are clearly visible on the surface, and sometimes a fifth one is noticeable. The buccal surface is almost square with slightly convex sides. An enamel ridge is often visible on the palatal side. Such teeth have three roots, in 85% of cases there are 4 root canals, much less often - 3.
• The second lower molars already have five cusps with less deep grooves than those of “adult” teeth. Both roots are flattened and curved at the top. In 85% of cases, teeth have three canals, although there are exceptions.

With the eruption of permanent, “adult” molars, the change of teeth begins, which lasts from 5-7 to 12-14 years. It is the first molars, which do not have primary analogues, that hold the bite, ensuring the correct placement of the remaining permanent teeth in the arch.