Central and lateral incisors of the lower jaw

The central and lateral incisors of the mandible are the smallest teeth. The central incisors are smaller than the lateral incisors. The crowns of the mandibular incisors are narrow and long and chisel-like in shape. The approximal surfaces are almost parallel. On the approximal surface of the crown it can be seen that its neck has a pronounced moon-shaped shape.

The vestibular surfaces of the crowns are slightly convex or flat. At the cutting edge, two vertical grooves are visible on them. The oral surfaces of the crowns are smooth, concave, triangular in shape, and the dental cusps are poorly defined. The sign of angles in the central incisors is absent, in the lateral incisors it is weakly expressed, and the distal angle may be higher than the medial one.

The sign of curvature in the lateral incisors is barely noticeable.

Canine of the lower jaw The canine of the lower jaw has a massive crown, tapering towards the edge on the vestibular and oral sides.

On the vestibular side, the crown is divided by a longitudinal ridge into two facets: medial - smaller and distal - larger. The cutting edge is created by two segments converging at an angle (medial - smaller and distal - larger), forming a cutting cusp at the top of the angle. On the oral side there is a pronounced dental tubercle.

The approximal sides of the canine converge at a slight angle to the neck. The largest diameter (equator) of the crown in the vestibular-oral direction is closer to the neck, and in the medial-distal direction it is close to the cutting edge.

The crowns of the canines of the lower jaw protrude from the arch of the dentition in three directions: they “stand” somewhat in relation to the vestibular and oral surfaces of the crowns of adjacent teeth, the cutting edges protrude above the cutting edges of the incisors.

Mandibular first premolar

The crown of the first premolar of the mandible is inclined orally in relation to the root, the chewing surface has a rounded shape and is narrowed in the vestibulo-oral direction.

The vestibular surface is similar in shape to the vestibular surface of the canine. It is divided by a longitudinal ridge into facets: medial - smaller and distal - larger.

The vestibular part of the chewing surface has a tubercle with two slopes - medial and distal.

The oral surface is narrower and shorter than the vestibular one, which is due to the less developed oral tubercle.

The approximal surface has convexities that are located closer to the chewing surface. The crown narrows toward the neck.

The chewing surface of the mandibular premolar has a more rounded shape than the chewing surface of the maxillary premolar, which is oval in shape.

There are two tubercles on the surface: the vestibular - larger and the oral - smaller.

The cusps are connected by enamel ridges located along the edge of the approximal surfaces and in the middle of the chewing surface.

Medially and distally from the tubercles there are symmetrically located depressions. The vestibular tubercle is inclined towards the oral tubercle.

The oral cusp is blunt and often does not make occlusal contact with the occlusal surface of the antagonist. Second premolar of the mandible The second premolar is larger in size than the first premolar of the mandible.

The difference between the first premolar and the second is that in the first premolar the tip of the vestibular cusp lies much higher than the top of the oral cusp, the crown of the first premolar is narrowed towards the oral side, the crown of the second premolar is rounded.

The crown of the second premolar of the mandible is larger than the crown of the first premolar, it can have a different shape and be slightly inclined orally.

The axis of the crown and the axis of the root form a smaller angle than that of the first premolar. The shape of this molar varies greatly, but most often repeats the shape of larger molars. The similarity of shape with larger molars is greater, the more the crown is developed.

The chewing surface most often has three tubercles, but a chewing surface with four tubercles is considered normal. Sometimes the third molar is the size of a premolar or even smaller.

Teeth of the lower jaw

The vestibular surface of the crown is shaped like the vestibular surface of the first premolar of the mandible. The oral surface is significantly larger than that of the first premolar, which is due to the greater development of the oral cusp.

The approximal and medial surfaces are slightly convex and converge towards the neck of the tooth. The chewing surface is round in shape.

It has two, and more often three, tubercles: vestibular and two oral. The vestibular tubercle is blunt, slightly inclined orally.

The oral cusp is sharp, more pronounced than that of the first premolar, and located slightly higher than the vestibular one.

As with the first premolar, the mesial and distal sides of the chewing surface are formed by enamel folds connecting the cusps.

The groove separating the vestibular tubercle from the oral tubercle is usually sharply defined; sometimes a groove extends from it, dividing the oral tubercle into medial and distal sections, which turns the tooth into a tricuspid one.

Mandibular first molar

The shape of the crown of the first molar approaches the shape of a cube.

The vestibular surface is convex and at the edge of the chewing surface is inclined towards the oral side. The oral surface is also convex, but it is smaller than the vestibular one.

The medial surface is larger than the distal one and more convex. Both approximal surfaces converge sharply towards the neck.

The chewing surface is rectangular in shape, its medial-distal size is larger than the vestibular-oral one.

The chewing surface has five cusps: three vestibular and two oral. The largest tubercle is the medial vestibular one, the smaller one is the distal vestibular one.

The tubercles are separated from each other by grooves. The two main grooves run from the medial to the distal edge and from the oral to the vestibular.

They intersect in the middle of the chewing surface at a right angle, and the longitudinal groove does not reach the approximal edges of the chewing surface, while the transverse groove passes in the form of a groove onto the vestibular and oral surfaces of the tooth.

Mandibular second molar The crown of the second molar is slightly smaller than the crown of the first molar.

The chewing surface has four cusps: two vestibular, of which the medial one is larger and higher than the distal one, and two oral ones, equal in size.

The vestibular tubercles are located above the oral ones and have a rounded shape. Oral tubercles are pointed in shape.

The approximal surfaces are almost parallel and somewhat narrow at the neck. The vestibular surface is divided into two halves by a relatively deep groove.

The groove ends at the beginning of the vestibular convexity. The oral surface is also divided by a groove that reaches the oral convexity of the tooth crown. This groove is shorter than the vestibular one.

The oral convexity is located above the vestibular one. Mandibular third molar The crown of the third molar is usually smaller than the crown of the second molar and can be of various shapes.

However, this phenomenon is observed less frequently than in the opposing maxillary third molar. The chewing surface usually consists of four tubercles, but sometimes five tubercles are found.

Therapeutic dentistry. Textbook Evgeniy Vlasovich Borovsky

3.3.1. Anatomical structure of teeth

A person's teeth change only once. The teeth of the mixed bite are called milk teeth, or temporary teeth (dentes decidui). Their eruption begins at the 6-7th month of life and ends at 2.5-3 years. At the age of 5-6 years, permanent teeth (dentes permanentes) begin to erupt, and by the age of 13 dairy products are completely replaced permanent. Number of dairy and permanent teeth unequal: there are only 20 teeth in the primary dentition, since the small molars and third major molars are missing. The anatomical formula of the teeth of the temporary occlusion is 2.1.2, i.e. on each side of both the upper and lower jaw there are 2 incisors, 1 canine and 2 large molars.

Rice. 3.6. Dentition of permanent dentition.

There are 32 teeth in the permanent dentition (Fig. 3.6). Their anatomical formula is 2.1.2.3, i.e. 2 incisors, 1 canine, 2 small and 3 large molars.

In the teeth of temporary and permanent dentition there are crown(corona dentis) - part of the tooth protruding into the oral cavity; tooth root(radix dentis), which is located in the alveolus; neck of the tooth(cervix dentis) - a slight narrowing at the border between the crown and root of the tooth. At this point, the enamel covering of the tooth crown ends and the cement (cementum), which covers the tooth root, begins. In the area of ​​the neck of the tooth, a circular ligament is attached, the fibers of which on the opposite side are woven into the bone of the alveoli, gum, and are also directed to the necks of neighboring teeth.

Inside the tooth there is tooth cavity(cavitas dentis), which is divided into coronal part(cavitas coronale) and tooth root canal, or root canal(canalis radicis dentis), in the apical area the root ends narrow apical(apical) hole(foramen apicis dentis).

Teeth crowns have several surfaces. In the group of anterior (frontal) teeth they are as follows: vestibular(fades vestibularis), lingual(facies lingualis), two contact surfaces, one of which faces the midline and is called middle surface(facies medialis), and the other is outward and is called lateral surface(facies lateralis). The line of convergence of the labial and lingual surfaces forms cutting edge(margo incisalis). In the group of small molars and large molars there are vestibule(facies vestibularis), linguistic(facies lingualis), chewing(facies masticatoria) surfaces. From contact surfaces(facies contactis) one is called anterior (facies anterior), the other - rear(facies posterior).

Rice. 3.7. Signs of a tooth’s group affiliation, a – a sign of crown curvature; b - sign of crown angle; c, d - root sign

Each tooth has anatomical characteristics that make it possible to determine its group affiliation.

Such signs are the shape of the crown, cutting edge or chewing surface, and the number of roots. Along with this, there is a sign that the tooth belongs to the right or left jaw: a sign of curvature of the crown, angle, root.

A sign of crown curvature is manifested in the fact that the greatest convexity of the vestibular (dental, cheek) surface is located medially (Fig. 3.7, a).

The sign of the crown angle is expressed in the fact that the medial surface and the cutting edge of the incisors and canines form a more acute angle than the angle formed by the cutting edge and the lateral surface (Fig. 3.7b).

The sign of the root is that the roots of the incisors and canines deviate in the posterolateral direction, and the roots of small and large molars - in the posterior direction from the longitudinal axis of the root (Fig. 3.7, c, d).

3.3.1.1. Baby teeth

The anatomical structure of baby teeth is basically identical to the structure of permanent teeth. They are distinguished from permanent teeth by their smaller size, more pronounced width of the crowns compared to their height, and bluish color. In the neck area, the edge of the enamel is somewhat thickened and protrudes in the form of a roller. In the alveolar arch, the primary teeth are located more vertically, which is due to the location of the rudiments of permanent teeth behind the roots of the primary teeth. The primary (temporary) teeth lack a group of small molars.

Incisors(dentes incisivi). The crowns of the temporary incisors of the upper and lower jaws are similar to the crowns of the permanent teeth of the same name. The labial surface is convex; the central incisors of the upper jaw lack longitudinal grooves, which are well pronounced in the permanent central incisors. All incisors have a significantly rounded lateral angle. The roots of the teeth are thin, round in shape, the central incisors have well-defined signs of an angle: the medial angle is more acute than the lateral one.

However, the lateral angle of the maxillary lateral incisor is more rounded than that of the central one. The roots of the central incisors of the upper jaw are wider, and their apices, as a rule, are deflected distally and forward. The crowns of the central incisors are small, the roots are flattened, with grooves on the medial and lateral surfaces.

fangs(dentes canini). The size of the temporary canines of the upper and lower jaws is smaller than the permanent ones, and their crown has more convex surfaces.

Temporary canines are characterized by the presence of a sharp tooth on the cutting edge. The canine crown of the lower jaw is narrower than the canine crown of the upper jaw. The root of the fangs is round in shape with a slightly curved apex.

Large molars, or molars(dentes molares) Temporary large molars of the upper jaw, like permanent ones, have three roots - two buccal and one palatal. However, compared to permanent teeth, the roots of temporary teeth diverge to a greater extent due to the fact that the rudiments of permanent small molars are located between them. There are two options anatomical structure crowns of the first large molar; both options are equally common. In one case, the crowns are similar in structure to the crowns of the first small molar of permanent dentition - they have buccal and lingual cusps separated by a groove. In the second case, the crown is elongated in the anteroposterior direction. The buccal cusp has three small protrusions, the lingual cusp is somewhat smaller, but protrudes more noticeably above the chewing surface. The second large molar of the upper jaw has a crown, the structure of which is similar to the structure of the crown of the first permanent large molar of the upper jaw. The second has 4 cusps, of which the anterior and posterior lingual are connected by an enamel ridge. An abnormal additional tuberosity is noted in approximately 90% of cases.

Temporary large molars of the lower jaw have two widely spaced roots, between which, as well as between the roots of the molars of the upper jaw, the rudiments of small molars are laid.

Rice. 3.8. Central incisor of the upper and lower jaws, a - vestibular surface; b - lingual, c - lateral; g - cross section; d - longitudinal section

The crown of the first molar has 4 cusps on the chewing surface, of which the anterior buccal cusp is connected to the anterior lingual ridge using a small enamel ridge. The structure of the crown of the second molar is similar to the structure of the crown of the permanent molar of the lower jaw and has 5 cusps.

3.3.1.2. Permanent teeth

Incisors(dentes incisivi). Maxillary central incisors(Fig. 3.8) are the largest of the group of incisors. The vestibular and lingual surfaces, converging, form a cutting edge, which in newly erupted teeth has 3 tubercles, which are quickly erased later. The vestibular surface is slightly convex; there are two faint grooves on it, running approximately from the central part of the crown towards the cutting edge and ending between its buffs. The lingual surface is triangular and concave. Along the edges of the crown there are vaguely defined ridges. Converging at the neck of the tooth, they form a tubercle, the size of which varies; at greater tuberosity a hole is formed at the point where the rollers converge. The median and lateral walls are convex, triangular in shape with the apex at the cutting edge and the base at the neck of the tooth. The root is cone-shaped, the front surface is slightly wider than the back and in cross section it approaches the shape of a triangle. There are longitudinal grooves on the middle and lateral surfaces of the root. Signs of curvature and angle are well expressed; the root sign is not expressed, but in general the root is deviated in the posterolateral direction, in 100% of cases there is one canal.

Rice. 3.9. Lateral incisor of the upper and lower jaws, a - vestibular surface; b - lingual; c - lateral; g - cross section; d - longitudinal section.

Maxillary lateral incisors(Fig. 3.9) are smaller in size than the central ones. The vestibular surface is convex, the middle surface forms a blunt angle when transitioning to the cutting edge. The lateral angle is largely rounded. The lingual surface is concave and has the shape of a triangle, which forms well-defined lateral ridges. Converging at the neck of the tooth, they form a tubercle, and at the places where they converge, a well-defined pit usually appears. The root is compressed from the sides and the cut is oval in shape; there are grooves on the sides. As in the central incisor, the sign of angle and curvature is well expressed and, to a lesser extent, sign of the root 100% of cases available one channel.

Mandibular central incisors(see, Fig. 3.8) significantly smaller than the incisors of the upper jaw. Their crowns are elongated in the vertical direction, the labial surface is slightly convex, and the lingual surface is concave in the vertical direction. The lateral ridges are not pronounced, so the tubercle is almost absent. The crowns of the central incisors are narrower than the lateral ones. Their lateral surfaces are almost vertical, while in the lateral incisors the lateral surface from the cutting edge to the neck is directed with an inclination so that the crown at the cutting edge is wider than at the neck. The root of both incisors is compressed from the sides. All signs are weakly expressed in the central incisors. Their belonging to one side or another is determined by the groove on the root, which is more pronounced on the lateral surface than on the medial. The canals of the central incisors of the lower jaw are narrow. In 70% of cases there is one and in 30% - two channels.

Mandibular lateral incisors(see Fig. 3.9) are determined by the angle, curvature of the crown and root, although these signs are weakly expressed. The tooth cavity in the incisors of the upper and lower jaws is formed by the vestibular, lingual and two lateral walls, which have a triangular shape. The widest part of the cavity is located at the level of the tooth neck; constantly narrowing, it turns into a canal. In the lateral incisors, the canals are somewhat narrower than in the central ones, and are laterally compressed. In some cases, channels may have a series of blindly ending branches.

Rice. 3.10. Fang of the upper and lower jaws, a - vestibular surface; b - lingual, c - lateral, d - transverse section; d - longitudinal section.

In the lateral incisors of the lower jaw, in the lower third, the canal branches deltoidally and reunites at the root apex. In 56% of cases there is one and in 44% there are two channels.

fangs(dentes canini). Maxillary canines(Fig. 3.10) have a conical shape and are the most developed of the group of single-rooted teeth. The cutting edge of the fang is not formed by a straight line, like the incisors, but consists of two segments converging at an angle, which form a well-defined tubercle at the point of convergence. Of the lines that form it, the medial one is always shorter than the lateral one. The labial surface is convex and is divided into two facets by a vaguely defined ridge - the smaller, medial, and the larger, lateral. The lingual surface is convex and also divided by ridges into two facets, which have depressions and sometimes even pits. At the neck of the tooth, the ridge turns into a well-defined tubercle. The contact surfaces are triangular in shape. The root is well developed, cone-shaped, slightly compressed laterally, its lateral surface is more convex. Both sides have faint grooves. Root tip often curved. Well expressed signs angle and curvature. In 100% of cases there is one channel.

Canines of the lower jaw(see Fig. 3.10) slightly smaller compared to the canines of the upper jaw; they differ little in shape. The labial surface is convex, the ridge is poorly defined, so the division into medial and lateral facets is unclear. The lingual surface is somewhat concave, the lingual tubercle is well defined. Crown height of vestibular and lateral surfaces some exceeds the height of the lingual and medial surfaces. The root has well-defined grooves on the lateral surfaces.

Figure 3.11. The first small molar of the upper and lower jaws.

a - vestibular surface, b - lingual; c - lateral, g - chewing; d - cross section, f - longitudinal section.

The canine cavities of the upper and lower jaws are wide and fusiform. The coronal part of the cavity directly passes into the root canal. IN fangs In the lower jaw, there are sometimes two canals (in 6% of cases) - labial and lingual.

Small molars, or premolars(dentes premolares). U first small molar of the upper jaw(Fig. 3.11) the shape of the crown approaches rectangular, the lingual surface is somewhat smaller than the buccal surface, the diameter of the crown is larger in the bucco-lingual direction. The buccal surface is convex, a sign of crown curvature is clearly visible, which in these teeth can often be reversed, i.e., the back part of the buccal surface is more convex and the front part is more sloping. The buccal surface merges into the lateral surfaces, forming rounded corners. The lateral surface has the shape of a rectangle, convex, and the rear surface is convex to a greater extent. They smoothly, without forming angles, transform into a convex lingual surface. The chewing surface is formed by two tubercles, of which the buccal one is slightly larger. Between the tubercles there is a fissure, which is limited at the edges by small transverse grooves, as a result of which ridges are formed along the edges of the chewing surface. The root is compressed in the anteroposterior direction; there are deep grooves on the lateral surfaces. At the apex of the tooth root there is a split into two independent roots - buccal and lingual. The border of root division is different, most often at the apex of the root, but it can also be in its middle part and even closer to the cervical region. The higher the root splitting border, the more the masticatory surface cusps converge. In the tooth Fine all expressed distinctive signs that allow you to identify the teeth of the right or left half of the jaw. In the second small molars of the upper jaw, there is often one canal with a funnel-shaped mouth, which is located in the center of the bottom of the cavity. Often (in 13.5% of cases) these teeth have two canals, and then their mouths are located respectively closer to the buccal and lingual walls of the tooth cavity. In 85% of cases there is two channels, in 6% - three and in 9% of cases - one channel.

Rice. 3.12. The second small molar of the upper and lower jaws, a - vestibular surface; b - lingual; c - lateral; g - chewing; d - cross section; e - longitudinal section; g - longitudinal section of a small molar of the upper jaw with two canals.

Second small molar of the upper jaw(Fig. 3.12) differs little in shape from the first, but is slightly smaller in size. The vestibular surface is convex and has a vaguely defined longitudinal ridge. The contact surfaces are convex, with the rear surface being more convex than the front. Both the buccal and lingual surfaces are somewhat smaller than those of the first small premolar tooth.

On the chewing surface there are two tubercles of the same size. The root, as a rule, is single, has a cone-shaped, slightly flattened shape, with small grooves on the lateral surfaces. In the first small molars of the upper jaw, the bottom of the cavity has a saddle shape. The canals - buccal and lingual - are narrow, their mouths are located at the edges of the bottom of the cavity. In 75% of cases there is one channel, in 24% there are two and in 1% of cases there are three channels.

First small molar of the lower jaw(see Fig. 3.11) are smaller in size than the maxillary premolars. The rounded crown on the chewing surface has two cusps, of which the buccal one is larger than the lingual one. The cusps are separated by a small groove, which is always located closer to the lingual cusp. Lumps on the anterior and posterior surfaces connected by enamel rollers. In other cases An enamel ridge runs from the middle of the buccal cusp to the lingual one, and then two pits are formed on its sides on the chewing surface. The buccal surface is convex, the sign of curvature is well expressed, the contact surfaces are also convex and gradually transform into the lingual surface. The root is oval in shape; there are faint grooves on the front and back surfaces. Often the crown and root are located in relation to each other at an obtuse angle with an inclination towards the tongue. The root sign is well expressed. In 74% of cases there is one and in 26% - two channels.

Second small molar of the lower jaw(see Fig. 3.12) larger than the first one small molar of the same jaw. The chewing surface consists of two equally well-developed tubercles; There are enamel ridges along the edges between them. Between the tubercles there is a deep groove; often an additional groove extends from it, which divides the lingual cusp into two, turning the tooth into a tricuspid one. The buccal surface does not differ from the buccal surface of the first premolar, but the contact surfaces are somewhat larger, convex and gradually transform into the lingual surface. Thanks to the well-developed lingual cusp, it is also larger than the lingual surface of the first small molar. The cone-shaped root is more developed in comparison with the first small molar. The coronal part of the tooth cavity in small molars is compressed in the anteroposterior direction and has the shape of a gap with two protrusions corresponding to the cusps of the crown. In the small molars of the lower jaw, the coronal cavity is also compressed in the anteroposterior direction, there is only one canal and has a funnel-shaped mouth. In the second small molar, a canal branching sometimes occurs in the apical part.

Rice. 3.13. The first large molar of the upper and lower jaws.

a - vestibular surface, b - lingual; c - contact: g - chewing; d - cross section; e - longitudinal section.

Large molars, or molars. First large molar of the upper jaw(Fig. 3.13) on the chewing surface has 4 tubercles, separated from each other by grooves. One of the grooves, starting on the front surface, crosses the chewing surface and moves to the buccal surface, where it continues to the neck of the tooth. This groove separates the anterior buccal tubercle. The second groove begins on the posterior surface, passes to the chewing and lingual surfaces, separating the posterior lingual tubercle. The third groove is located in the middle of the chewing surface, connects the first two and separates the anterior and posterior lingual cusps. The buccal cusps are conical in shape, while the lingual cusps are more rounded. The anterior tubercles are always larger than the posterior ones. The buccal surface is convex, divided by a groove, and has a well-defined sign of crown curvature. The posterior surface is more convex than the anterior one, but its dimensions are larger than that of the posterior one. The lingual surface is more convex than the buccal surface, but smaller, and has a faint groove that passes onto it from the chewing surface. On the anterior lingual tubercle there is usually an abnormal (additional) tubercle, expressed to a greater or lesser extent, but never reaching the masticatory surface. The tooth has three well-defined roots: one palatal, cone-shaped, and two buccal roots - anterior and posterior (the latter is smaller than the anterior one). Both roots are compressed in the anteroposterior direction. In 57% of cases there are three, and in 4% there are four channels.

Rice. 3.14. The second large molar of the upper and lower jaws.

a - vestibular surface; b - lingual; c - contact, d - chewing, e - three variants of the chewing surface of the second large molar of the upper jaw; e - cross section; g - longitudinal section

Maxillary second molar(Fig. 3.14) has a different crown structure. The most common are 4 options: 1) the structure of the crown of the tooth approaches the shape of the crown of the first large molar, with the exception of the additional tubercle, which is always absent; 2) the crown of the tooth has the shape of a diamond. The anterior and posterior lingual cusps are closer together, the groove between them is only slightly noticeable; 3) the anterior and posterior lingual cusps merged in the anterior lingual direction; 4) the triangular crown has 3 cusps - one lingual and two buccal. The first and fourth forms of crowns are more common. The tooth has 3 roots, somewhat smaller in size compared to the first large molar. Sometimes there is a fusion of all the roots into one cone-shaped one, on which there are only grooves at the place of fusion. In other, more frequent cases, only the buccal roots grow together. In 70% of cases there are three and in 30% - four channels.

Third maxillary molar(Fig. 3.15) has a different shape and size. The crown can sometimes reach the size of the first molar or be significantly smaller than it, taking the form of a pin tooth. More often the crown has 3 cusps, somewhat less often - 4, but there may also be 5–6 cusps. The size and shape of tooth roots are also constant; their number can vary from 1 to 4–5. The cavity of the maxillary molars has the shape of a rectangle or, as is more common in the second molars, an elongated triangle. The arch of the cavity is located at the level of the neck of the tooth, the horns protrude into the area of ​​the cusps of the crown. The mouths of the canals are located in the form of a triangle. There are usually three canals: a lingual, a wider one and two narrow buccal ones. Of these, the posterior buccal often branches into two canals that anastomose with each other.

Rice. 3.15. Third large molar of the upper and lower jaw,

a - vestibular surface; b - lingual; c - contact; g - chewing. d - cross section, f - longitudinal section

First large molar of the lower jaw(see Fig. 3.13) is the largest of the group of large molars of the lower jaw. On its chewing surface there are two grooves - a longitudinal one, located only within the boundaries of the chewing surface, and a transverse one, which begins on the buccal surface and, crossing the chewing surface, passes to the lingual surface. In the posterior buccal area of ​​the chewing surface there is an additional small groove extending from the transverse one. This arrangement of grooves forms 5 tubercles on the chewing surface: 3 buccal and 2 lingual. Very rarely, but still there are six-tubercle second molars. The buccal surface is convex, with a well-defined sign of crown curvature. The contact surfaces are similar to the corresponding surfaces of the first large molar of the upper jaw: the posterior surface of the crown is smaller and more convex than the anterior one. The lingual surface is convex and smaller in size than the buccal surface. The crown of the tooth is tilted towards the oral cavity. The tooth has two roots - anterior and posterior; they are flattened and their width is more pronounced in the buccolingual direction. There are longitudinal grooves on the surface of the roots. The exception is the posterior surface of the posterior root. The roots are slightly deviated posteriorly. In 65% of cases there are three, in 29% - four and in 6% of cases - two channels.

Second large molar of the lower jaw(see Fig. 3.14) is slightly smaller than the first, but has the same shape. A distinctive feature is the presence on the chewing surface of 4 identical-sized tubercles, formed by the intersection of two grooves. Very rarely there are 5 tubercles and also rarely - fusion of roots. The signs of the root are well expressed.

Lower third molar(see Fig. 3.15) can be of different shapes. However, this phenomenon is observed much less frequently than in the opposing third molar of the upper jaw. More often, the chewing surface consists of 4 tubercles, but five-tubercle third molars are also often found. There were even cases where the tooth had 6–7 cusps. In most cases there are two roots, but often they merge into one cone-shaped root. Occasionally there are several underdeveloped roots. The cavity of the large molars of the lower jaw, as well as the large molars of the upper jaw, follows the shape of the tooth. The coronal part of the cavity has a trapezoidal shape with a larger width of the anterior wall. The arch of the cavity lies at the level of the neck of the tooth, its 4 horns protrude into the cusps and, like the cusps of the crown, the anterior horns are slightly larger than the posterior ones. The coronal cavity passes into root canals, of which two are located in the anterior root and one, wider, in the posterior one. Channels can branch; There are often anastomoses between the anterior ones. The orifices of the canals are located in the form of a triangle, the apex of which faces the posterior canal.

author Fereydoun Batmanghelidj

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Teeth are organs that are part of the human chewing and speech apparatus. They, in combination with the tongue, lips, salivary glands and a number of muscles and bones, ensure normal chewing and swallowing of food and sound pronunciation. In an adult healthy person V oral cavity there are 32 teeth. Some people have fewer because congenital anomalies or dental interventions.

In the oral cavity, the teeth (dens) are located in two rows. Each of the masticatory organs occupies a specific dentofacial area. This segment consists, in addition to the tooth, of part of the jawbone, ligaments, blood vessels and alveoli - a depression in the bone covered with mucous membrane.

Baby teeth

Human teeth are characterized by two specific features. They are heterodont and thecodont.

Attention! Heterodontism is a specific anatomical structure in which teeth have a specific function when biting and chewing food and, therefore, have different shapes. Thecodontism is a structural feature of the masticatory apparatus in mammals and humans, in which the teeth are not fused with the jaw bones.

Permanent teeth appear in a person between 6 and 12 years of age. Before this period, there are 20 milk teeth (dentes decidui) in the oral cavity, which fully grow by 24 months.

Diagram of baby teething

Teeth	Age
Lower central incisors	6-7 months
Upper central incisors	8-9 months
Upper lateral incisors	9-11 months
Lower lateral incisors	11-13 months
Upper molars	12-15 months
Lower molars	12-15 months
Upper canines	16-18 months
Lower canines	18-20 months
Lower large molars	24-30 months
Upper large molars	24-30 months

The structure of the dentofacial apparatus in children has a number of features. This specificity should be taken into account both when caring for teeth and when treating them. There are the following features dentes decidui:

1. Enamel shade. Color baby tooth may vary from bright white to bluish. Sometimes, because of this color of the enamel, a child is mistakenly diagnosed with pulpitis.
2. Shape of teeth. Dentes decidui are low and wide, but thinner and sharper. There are serrations on the cutting edge of baby teeth, which wear out by the age of 4-5.
3. Baby teeth have a more rounded and convex shape. This is especially true for molars.
4. Dentes decidui have shorter roots than permanent teeth, but the root system is more branched.

Structure of a baby tooth

The anatomical structure of dentes decidui is in many ways similar to the structure of permanent teeth. Baby teeth are also covered with enamel, but it is thinner and softer, making it more susceptible to various injuries and damage.

Attention! It is necessary to regularly bring your child for preventive examinations to the dentist. Otherwise, superficial caries can very quickly lead to tooth destruction and the formation of pulpitis.

Directly under the enamel there is a fairly thin layer of dentin. It surrounds the coronal cavity and root canals. The tooth cavity is filled with pulp, dotted with vessels and nerves. In dentes decidui the amount of pulp is much greater than in permanent ones. She provides normal nutrition and the course of metabolic processes in dental tissues.

The structure of teeth in an adult

Teeth are the most important digestive organ in the oral cavity. If the integrity or absence of teeth is damaged, the process of primary mechanical processing of food masses, including biting, chewing, chopping and crushing food, is disrupted. In addition, the presence of teeth is necessary for an adult to breathe normally and pronounce sounds.

Over the course of a lifetime, people change their teeth once. Permanent teeth (dentes permanents) begin to form at 6-10 weeks of embryonic development, and are finally formed when the child is 4-6 years old.

The order of eruption of permanent teeth

Teeth	Age
Lower central incisors	5-7 years
Lateral incisors of the lower row	9-10 years old
Upper central incisors	6-8 years old
Upper row lateral incisors	9-10 years old
Top row canines	10-11 years old
The first small indigenous	9-10 years old
Second minor radicals	11-12 years old
Lower row canines	10-11 years old
Large molars of the first stage	5-6 years
Large molars of the second stage	12-13 years old
Large molars of the third stage	20-25 years

Attention! A tooth is a formation that cannot spontaneously recover when damaged. That is why it is necessary to carefully monitor their condition and undergo regular preventive examinations by a specialist.

A tooth is formed by a root and a crown. The crown rises above the gum. It is covered with strong and hard enamel. It is the enamel that protects the tooth from external influences. In a healthy person, this layer of the tooth is smooth, even and shiny. Brittle, yellow or grayish enamel with chips and cracks indicates pathologies of the dentofacial apparatus or general violations human health.

Attention! Enamel is one of the strongest tissues in the body. However insufficient care care of the oral cavity, smoking and calcium deficiency in the body can lead to a violation of its integrity. Through cracks in the enamel, pathogens can penetrate into the thickness of the tooth, causing caries or more severe disorders.

Directly below the enamel is dentin. This is the hard tissue that makes up the majority of the tooth and supports the enamel and protects the pulp. On average, dentin thickness varies from 2 to 5 mm. Dentin is softer than enamel, so it is more susceptible to destructive processes.

Dentin is penetrated by numerous tubules that diverge from the pulp towards the enamel. They are necessary to ensure normal metabolic processes inside the tooth.

The permanent tooth consists of three types of dentin:

1. Primary – formed at the stage of tooth formation, before its eruption.
2. Replacement – ​​is formed throughout the entire period of the tooth’s existence.
3. Tertiary – appears when a tooth is damaged in the area of ​​trauma or caries. Develops as a reaction to local irritation.

The pulp is located in the root part of the tooth. This is a loose substance that fills the cavities of the dentes decidui. Along the perimeter of the pulp, specific odontoblast cells are located in several layers, the processes of which diverge into dentinal tubules. Also soft fabric The tooth is dotted with many arterioles, venules and nerve roots.

The roots of the tooth extending into the gums are not covered with enamel. On top of the dentin there is a layer of cement, which, with the help of collagen fibers, is attached to the periodontium - a specific dense connective tissue located between the root and the alveolus. The roots of the tooth go deep into the thickness of the alveoli.

Attention! Damage to the roots of a tooth is a serious pathology that requires long-term treatment and, often, resection. In some cases, the violation leads to a protracted inflammatory process, which results in the formation of a cyst, which is why the tooth has to be removed.

Types of permanent teeth

Human teeth are heterodont. They vary in both shape and size due to their purpose. Some of them are designed for biting food, others are for chewing. All types of teeth can be divided into four groups:

• incisors: central and lateral;
• fangs;
• premolars;
• molars are large molars.

In dental practice, for convenience and brevity in designating the dental system, a dental formula is used. The molars are designated in Arabic numbers from 1 to 8.

Specifics of the structure of the teeth of the upper row

The basis of the dentition consists of incisors, canines, premolars, as well as molars of the first and second order. Molars of the third stage, which are called wisdom teeth, usually appear in people aged 20-25 years and are often subject to removal, as they can lead to malocclusion and other unpleasant consequences:

Attention! If, during the eruption of the third molars, the patient suffers strong pain, a putrid odor appears in the mouth, and touching the gums causes a sharp increase in pain syndrome, you need to urgently consult a doctor.

Specifics of the structure of the teeth of the lower row

The teeth of the lower jaw have the same names and structures as the teeth of the upper row, but they also have several characteristic differences:

1. The incisors of the lower jaw are the smallest. They have a fairly thin and narrow crown and one small root.
2. The canines of the lower row are deflected posteriorly, they have a more curved shape. Often the lower canines are shorter than the upper ones.
3. The lower premolars have a flatter and more rounded shape. Both the first and second premolars have only one straight, short root.

Teeth are organs designed to process food masses, perform the normal act of breathing and pronounce sounds. The human dentofacial apparatus has a rather complex structure and its own complex of nerves and vessels that provide nutrition and innervation to dental tissues. Such complex structure necessary to keep your teeth intact for as long as possible.

Video -

Video - Tooth structure. Types and functions of teeth

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Human teeth are an integral part chewing-speech apparatus, which, according to modern views, is a complex of interacting and interconnected organs that take part in chewing, breathing, and the formation of voice and speech. This complex includes: solid support - the facial skeleton and the temporomandibular joint; chewing muscles; organs designed for grasping, moving food and forming a bolus of food, for swallowing, as well as the sound-speech apparatus: lips, cheeks, palate, teeth, tongue; organs for crushing and grinding food - teeth; organs that serve to soften and enzymatically process food are the salivary glands of the oral cavity.

Teeth are surrounded by various anatomical structures. They form metameric dentition on the jaws, so the area of ​​the jaw with the tooth belonging to it is designated as dentofacial segment. There are dentofacial segments of the upper jaw (segmenta dentomaxillares) and lower jaw (segmenta dentomandibularis).

The dentofacial segment includes the tooth; the dental alveolus and the part of the jaw adjacent to it, covered with mucous membrane; ligamentous apparatus, fixing the tooth to the alveolus; vessels and nerves (Fig. 1).

Rice. 1.

1 - periodontal fibers; 2 - alveolar wall; 3 - dentoalveolar fibers; 4 - alveolar-gingival branch of the nerve; 5 - periodontal vessels; 6 - arteries and veins of the jaw; 7 - dental branch of the nerve; 8 - bottom of the alveoli; 9 - tooth root; 10 - neck of the tooth; 11 — tooth crown

Human teeth belong to the heterodont and thecodont systems, to the diphyodont type. First, milk teeth (dentes decidui) function, which appear completely (20 teeth) by the age of 2 years, and then are replaced permanent teeth(dentes permanents) (32 teeth) (Fig. 2).

Rice. 2.

a - upper jaw; b - lower jaw;

1 - central incisors; 2 - lateral incisors; 3 - fangs; 4 - first premolars; 5 - second premolars; 6 - first molars; 7 - second molars; 8 - third molars

Parts of a tooth. Each tooth (dens) consists of a crown (corona dentis) - a thickened part protruding from the jaw alveolus; neck (cervix dentis) - the narrowed part adjacent to the crown, and root (radix dentis) - the part of the tooth lying inside the alveolus of the jaw. The root ends apex of tooth root(apex radicis dentis) (Fig. 3). Functionally different teeth have an unequal number of roots - from 1 to 3.

Rice. 3. Tooth structure: 1 - enamel; 2 - dentin; 3 - pulp; 4 - free part of the gum; 5 - periodontium; 6 - cement; 7 - tooth root canal; 8 - alveolar wall; 9 — hole in the apex of the tooth; 10 - tooth root; 11 - neck of the tooth; 12 — tooth crown

In dentistry there are clinical crown(corona clinic), which is understood as the area of ​​the tooth protruding above the gum, as well as clinical root(radix clinic)- the area of ​​the tooth located in the alveolus. The clinical crown increases with age due to gum atrophy, and the clinical root decreases.

Inside the tooth there is a small dental cavity (cavitas dentis), the shape of which is different in different teeth. In the crown of a tooth, the shape of its cavity (cavitas coronae) almost repeats the shape of the crown. Then it continues to the root in the form root canal (canalis radicis dentis), which ends at the tip of the root hole (foramen apices dentis). In teeth with 2 and 3 roots there are, respectively, 2 or 3 root canals and apical foramina, but the canals can branch, bifurcate and reconnect into one. The wall of the tooth cavity adjacent to its closure surface is called the vault. In small and large molars, on the occlusal surface of which there are chewing tubercles, corresponding depressions filled with pulp horns are noticeable in the vault. The surface of the cavity from which the root canals begin is called the floor of the cavity. In single-rooted teeth, the bottom of the cavity narrows funnel-shaped and passes into the canal. In multi-rooted teeth, the bottom is flatter and has holes for each root.

The tooth cavity is filled pulp of the tooth (pulpa dentis)- loose connective tissue of a special structure, rich in cellular elements, vessels and nerves. According to the parts of the tooth cavity, they are distinguished crown pulp (pulpa coronalis) And root pulp (pulpa radicularis).

General tooth structure. The hard base of the tooth is dentin- a substance similar in structure to bone. Dentin determines the shape of the tooth. The dentin that forms the crown is covered with a layer of white dental enamel (enamelum), and root dentin - cement (cementum). The junction of the crown enamel and root cement is at the neck of the tooth. There are 3 types of connection between enamel and cement:

1) they are connected end-to-end;

2) they overlap each other (enamel overlaps cement and vice versa);

3) the enamel does not reach the edge of the cement and an open area of ​​dentin remains between them.

The enamel of intact teeth is covered with a durable, lime-free cuticle enamel (cuticula enameli).

Dentin is the primary tissue of teeth. Its structure is similar to coarse-fibered bone and differs from it in the absence of cells and greater hardness. Dentin consists of cell processes - odontoblasts, which are located in the peripheral layer of the tooth pulp, and the surrounding main substance. It contains a lot dentinal tubules (tubuli dentinales), in which the processes of odontoblasts pass (Fig. 4). In 1 mm 3 of dentin there are up to 75,000 dentinal tubules. In the dentin of the crown near the pulp there are more tubes than in the root. The number of dentinal tubules varies in different teeth: in incisors there are 1.5 times more of them than in molars.

Rice. 4. Odontoblasts and their processes in dentin:

1 - mantle dentin; 2 - peripulpar dentin; 3 - predentin; 4 - odontoblasts; 5 - dentinal tubules

The main substance of dentin, lying between the tubules, consists of collagen fibers and their adhesive substance. There are 2 layers of dentin: outer - mantle and inner - peripulpar. In the outer layer, the fibers of the main substance run at the top of the tooth crown in the radial direction, and in the inner layer - tangentially with respect to the tooth cavity. In the lateral sections of the crown and in the root, the fibers of the outer layer are located obliquely. In relation to the dentinal tubules, the collagen fibers of the outer layer run parallel, and the inner layer runs at a right angle. Mineral salts (mainly calcium phosphate, calcium carbonate, magnesium, sodium and hydroxyapatite crystals) are deposited between the collagen fibers. Calcification of collagen fibers does not occur. Salt crystals are oriented along the fibers. There are areas of dentin with slightly calcified or completely uncalcified ground substance ( interglobular spaces). These areas can increase during pathological processes. In older people, there are areas of dentin in which the fibers are also susceptible to calcification. The innermost layer of peripulpar dentin is not calcified and is called dentinogenic zone (predentin). This zone is the place constant growth of dentin.

Currently, clinicians distinguish the morphofunctional formation endodontium, which includes pulp and dentin adjacent to the tooth cavity. These dental tissues are often involved in the local pathological process, which led to the formation of endodontics as a branch of therapeutic dentistry and the development of endodontic instruments.

The enamel consists of enamel prisms (prismae enameli)- thin (3-6 microns) elongated formations, running in waves through the entire thickness of the enamel, and gluing them together interprismatic substance.

The thickness of the enamel layer varies in different parts of the teeth and ranges from 0.01 mm (at the neck of the tooth) to 1.7 mm (at the level of the chewing cusps of the molars). Enamel is the hardest tissue of the human body, which is explained by its high (up to 97%) content of mineral salts. Enamel prisms have a polygonal shape and are located radially to the dentin and the longitudinal axis of the tooth (Fig. 5).

Rice. 5. The structure of the human tooth. Histological specimen. SW. x5.

Odontoblasts and their processes in dentin:

1 - enamel; 2 - oblique dark lines - enamel stripes (Retzius stripes); 3 — alternating enamel stripes (Schreger stripes); 4 - tooth crown; 5 - dentin; 6 - dentinal tubules; 7 - neck of the tooth; 8 - tooth cavity; 9 - dentin; 10 - tooth root; 11 - cement; 12 - tooth root canal

Cementum is coarse fibrous bone, consisting of main substance, impregnated with lime salts (up to 70%), in which collagen fibers run in different directions. The cement on the root tips and on the interroot surfaces contains cells - cementocytes, lying in the bone cavities. There are no tubes or vessels in the cement; it is nourished diffusely from the periodontium.

The root of the tooth is attached to the alveolus of the jaw through many bundles of connective tissue fibers. These bundles, loose connective tissue and cellular elements form the connective tissue membrane of the tooth, which is located between the alveolus and cement and is called periodontium. The periodontium plays the role of the internal periosteum. This attachment is one of the types of fibrous connection - dentoalveolar connection (articulation dentoalveolaris). The set of formations surrounding the tooth root: periodontium, alveolus, the corresponding section of the alveolar process and the gum covering it is called periodontal (parodentium).

The tooth is fixed using periodontal tissue, the fibers of which are stretched between the cement and the bone alveolus. The combination of three elements (bone dental alveolus, periodontium and cementum) is called supporting apparatus of the tooth.

The periodontium is a complex of connective tissue bundles located between the bone alveoli and cement. The width of the periodontal gap in human teeth is 0.15-0.35 mm near the mouth of the alveolus, 0.1-0.3 mm in the middle third of the root, and 0.3-0.55 mm at the root apex. In the middle third of the root, the leriodontal gap has a constriction, so it can be roughly compared in shape to an hourglass, which is associated with micromovements of the tooth in the alveolus. After 55-60 years, the periodontal fissure narrows (in 72% of cases).

Many bundles of collagen fibers extend from the wall of the dental alveoli to the cementum. In the spaces between the bundles of fibrous tissue there are layers of loose connective tissue in which cellular elements (histiocytes, fibroblasts, osteoblasts, etc.), vessels and nerves lie. The direction of bundles of periodontal collagen fibers is different in different sections. At the mouth of the dental alveolus (marginal periodontium) in the retaining apparatus, one can distinguish dentogingival, interdental and dentoalveolar group bundles of fibers (Fig. 6).

Rice. 6. Structure of the periodontium. Cross-section at the level of the cervical part of the tooth root: 1 - dentoalveolar fibers; 2 - interdental (interroot) fibers; 3 - periodontal fibers

Dental fibers (fibrae dentogingivales) start from the root cement at the bottom of the gingival pocket and spread fan-shaped outward into connective tissue gums.

The bundles are well expressed on the vestibular and oral surfaces and relatively weakly on the contact surfaces of the teeth. The thickness of the fiber bundles does not exceed 0.1 mm.

Interdental fibers (fibrae interdentaliae) form powerful beams 1.0-1.5 mm wide. They extend from the cementum of the contact surface of one tooth through the interdental septum to the cementum of the adjacent tube. This group of bundles plays a special role: it maintains the continuity of the dentition and participates in the distribution of chewing pressure within the dental arch.

Dentoalveolar fibers (fibrae dentoalveolares) start from the cementum of the root along the entire length and go to the wall of the dental alveoli. Bundles of fibers begin at the apex of the root, spread almost vertically, in the apical part - horizontally, in the middle and upper thirds of the root they go obliquely from bottom to top. On multi-rooted teeth, the bundles go less obliquely; in places where the root is divided, they follow from top to bottom, from one root to another, crossing each other. In the absence of an antagonist tooth, the direction of the beams becomes horizontal.

The orientation of bundles of periodontal collagen fibers, as well as the structure of the spongy substance of the jaws, are formed under the influence of functional load. In teeth devoid of antagonists, over time, the number and thickness of periodontal bundles become smaller, and their direction turns from oblique to horizontal and even oblique in the opposite direction (Fig. 7).

Rice. 7. Direction and severity of periodontal bundles in the presence (a) and absence of an antagonist (b)

Human anatomy S.S. Mikhailov, A.V. Chukbar, A.G. Tsybulkin

The condition of a person's teeth can say a lot about the body as a whole. From them one can judge the degree of functioning of the most important organs and vital systems.

A good specialist, based on the presence and nature of dental pathologies, can diagnose a number of chronic diseases in a patient.

If we consider this organ from the point of view of aesthetics, its role is difficult to underestimate. A beautiful, healthy smile is not only a source of pride modern man, but also the key to his success as a person, interlocutor, important factor career growth.

A tooth is an organ characterized by a sharp and strong bone structure, designed for high-quality processing of food. This is the general definition. However, one or another of their segments performs its own specific functions.

General schematic description of the structure of the organ:

• main clot nerve endings– the deepest part of the root zone;
• upper and lower jaw bones;
• apical branching;
• internal root canals;
• root cement - the hardest part of the root;
• venous vessels - run along the entire internal structure of the tooth;
• arteries are less pronounced compared to venous capillaries;
• nerve fibers are the smallest sensory processes;
• periodontium;
• gum - its lower part is hidden from view, the upper part envelops the base of the organ;
• periodontal recess;
• pulp;
• dentin – internal tissues of an organ;
• enamel - a durable surface shell - normally white or slightly milky in color, reliably protects the internal contents;
• fissure - relief depressions on the surface of the enamel.

Briefly, a tooth can be divided into three parts - the crown (everything that is on the surface), the root (everything that is below the gum), and the neck (the area where the crown and root separate). In normal condition, the neck is also hidden under the gum tissue and does not protrude to the surface.

Histology

Nature has taken sufficient care to internal structure an organ, thanks to which it successfully copes with the functions assigned to it and maintains (with proper care) its integrity and performance for many years.

If we consider it conditionally, the histology of the tooth looks something like this.

Enamel

Surface frame of the organ. Main goals:

• reliable protection of pulp and dentin from external mechanical influences;
• provides the function of chewing food fragments.

It is characterized by increased strength and is considered one of the hardest tissues in the human body. Color varies from almost white to shades of gray or yellow, which is considered normal.

The main component is inorganic compounds (more than 90%), water and organic matter.

It has a thickness (depending on the variety) from 1 to 6 mm. The thicker layer is in the lumpy area of ​​the molars.

A characteristic feature of the enamel structure is the possibility of both internal penetration of salivary secretions into it, and internal ones from the pulp.

The tissue does not regenerate at all, since it has no cells. It wears off over the years.

Dentin-enamel layer

R boundary tissue, which contains both fragments of enamel and dentin components. It has an uneven appearance, which increases the adhesion between tissues.

Dentine

Main functions:

• maintaining the integrity of the surface layer;
• maintaining the correct shape of the organ.

The tissue is calcified and serves as a kind of foundation for the tooth. A high-quality composition is much more pliable and softer than enamel, while being many times stronger than cement and bone.

It consists of 65% hydroxyapatite, 25% collagen, and 10% water.

The entire area is riddled with small tubules through which fluid passes, constantly nourishing and regenerating dentin.

Predentin

In some way, it is considered an incubator for restoring the structural integrity of dentin, along with which it creates the dividing walls of the pulp compartment.

Cement

Provides:

• protection of root dentin from external influences;
• participates in the general processes of organ restoration;
• reliably fixes periodontal threads with the neck;
• performs a support function.

The layer that protects and hides the root is filled with collagen, inorganic components and liquid, has a coarse fibrous structure, and is devoid of blood capillaries.

The highest strength is in the root apex area.

Pulp

Forms and nourishes dentin. Reacts strongly to external irritating factors. It is characterized by a loose consistency and a large number of nerve fibers and blood vessels.

As the body ages, the volume of the pulp decreases, turning into secondary dentin.

Periodontium

Takes on the entire load during the grinding process of food, distributes the force of pressure on the walls of the tooth. Stimulates regeneration processes in the periodontium.

Performs connecting function between the cementum and the border region of the alveoli. It has a cellular structure capable of renewal.

Additional information about the structure of teeth can be obtained from the video.

Maxillary units

The teeth of the upper jaw row, only at first glance, are completely identical to the lower organs. Upon closer inspection, the difference is quite significant.

Each individual organ performs a specific function and often does not look like its neighbor.

The upper teeth have the following arrangement:

• incisors are located in the central region of the row (called units in dental terminology);
• lateral incisors – twos. There is little difference in appearance from the central ones;
• fangs - almost an exact copy of the animal's teeth. More durable and sharp;
• premolars of the first and second stages(4 and 5, respectively) are very similar to each other;
• molars characterized by the most massive crown, the six is ​​larger, the seven is slightly smaller;
• Eights are known to everyone as wisdom teeth. Not every adult has them, which is quite normal. They resemble molars, are quite capricious, are painful to cut, and often have growth pathologies. I can still get sick at the teething stage.

Organs of the lower jaw

The organs of the lower jaw row, according to digital numerology, medical terminology and ordinal arrangement, exactly copy the teeth of the upper jaw.

But their qualitative structure is different:

• central incisors much smaller, tuberosity is almost not expressed;
• lateral somewhat larger than those located in the center, identical in internal structure;
• lower canines they recede somewhat more towards the rear than their upper “brothers”, in addition, they are significantly narrower;
• premolars– ones are more rounded, and twos are noticeably more massive;
• third representative of the molar class distinguished by its “individuality”. This tooth can look completely different in appearance.

Incisors

In the mouth, the incisors are located in the maxillary process. They have two components - the crown and the root part. The first is enamel, cement. The second is the root, connected to the crown, neck.

They have impressive parameters, a flat root, and are similar in shape to a chisel. The first of all segments of the jaw row to erupt onto the surface of the gums. Quite sharp, responsible for the beauty of a smile.

Functional purpose is high-quality chewing of food and grinding it into small fractions.

fangs

The shape is cone-shaped, slightly oblong. They cope well with the process of grasping and biting food.

The crown consists of two fragments - the mesial, smaller area, and the distal, more massive area..

The ridges connecting in the neck area are clearly visible on the surface. The root of the lower canine is somewhat shorter than the upper one, flatter, slightly bifurcating at the apex. The labial edge is wide and blunt.

Premolars

They are characterized by a prismatic-shaped crown and convex lingual tubercles. The contacting surfaces resemble a rectangle with a more curved back wall.

It has two convexities - buccal and palatal, and the first is much larger in size. The reverse principle of crown curvature often occurs. The root has the shape of a cone, somewhat compressed, with wide lobar grooves.

Their task is to efficiently grind food fragments, which is why they are also called chewing units.

Molars

The function is the same as the previous organs. The crown shape is rectangular. Above, on the chewing area, there are two palatal tubercles, and the same number of buccal tubercles, more pronounced.

They are separated from each other by a fissure. The lingual area is not too convex. Has several roots:

• palatal – the largest;
• anterior buccal – more developed, slightly flattened;
• The posterior buccal has less pronounced features.

Quite often, all three roots grow together and form a solid conical mass. Although this is a pathology, it is not too dangerous.

Watch the video about the types of teeth and their structure.

Problem eights

The most problematic segment of the jaw row is practically non-functional. Appearing much later than the others, it brings a lot of problems.

It is considered the third in the molar family. The root is too short, characterized by a strong and powerful trunk. root system multiple (from 2 to 5), with numerous bends and branches, which complicates its treatment.

It has a pronounced and characteristic coronal region. It is extremely rare to be anatomically correct. It has several convex surface tubercles. The most massive tooth, especially in the lower jaw.

Often it does not erupt completely and is covered by bone or gum tissue, which increases the risk of developing inflammatory processes. If positioned incorrectly, it interferes with neighboring teeth and leads to their loosening.

Dairy

There are about 20, fully formed in children by three years old . Features of the structure:

• small coronal part;
• thin, not very strong enamel, dentin is less mineralized in consistency compared to permanent teeth. The consequence is vulnerability to caries;
• the size of the pulp and root canal is larger than that of the root canal, which can also provoke the development of inflammation;
• the outer surface is less prominent;
• the root is somewhat curved on the outer side, not very long, so removing them is an almost painless process.

The main functions of baby teeth:

• grinding food;
• chewing;
• speech function in the process of word pronunciation;
• participation in learning useful substances children's body.

Despite their apparent hardness, teeth, no matter which of the groups described above they belong to, are a rather fragile system that requires care and careful handling. And then they will remain healthy and aesthetically pleasing for many years.

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