Teeth are among the most important organs of the human body. Each of them has a specific structure and performs a specific function. What teeth does the upper dentition consist of? What is the anatomy of the lower jaw? In these and other issues related to the structure of the teeth, we have to figure it out.
General information about teeth
Adult human can normally have from 28 to 32 teeth in the oral cavity. They are special formations with a complex structure. The visible part of each tooth is called the crown. One of its layers is dentin - a hard calcified material that does not have blood vessels. From above it is covered with tooth enamel. It acts as an outer protective shell.
The hidden part of the tooth is the root. It is placed in a depression in the jawbone called the alveolus. The root also has dentin. It is covered with a layer of cement, due to which the tooth is held in the recess of the jaw. Inside the bone formation is a pulp cavity, consisting of nerves, vessels and soft tissues.connective tissue.
Types and functions of teeth
Anatomy of the lower jaw and upper jaw divides bone formations located in the oral cavity into several varieties:
- large molars (molars);
- front (incisors);
- conical (fangs);
- small molars (premolars).
Teeth perform several important functions. First, they provide mechanical processing of food. Thanks to teeth, people can fully consume food. Secondly, these bone structures are involved in the formation of speech. They produce different sounds. Thirdly, teeth are part of a smile. They play an important aesthetic role.
You can also highlight the functions inherent in each specific tooth. The incisors located in the frontal part of the oral cavity provide cutting food. This is facilitated by their flat chisel-shaped crown. The fangs perform the function of crushing and capturing food, as they have a pointed cone shape. Molars and premolars are involved in grinding food, because their surface is quite wide.
The position of the teeth on the jaws
Anatomy of the lower jaw and upper dentition shows that bone formations are located in the form of arcs, each of which can be divided into 2 sides (quadrants). One quadrant in an adult consists of 8 teeth:
- 3 molars;
- 2 cutters;
- 1 fang;
- 2 premolars.
Some people have molars locatedthe last in the dentition and called "wisdom teeth", are absent. In each quadrant, not 8, but 7 bone formations are obtained. The absence of “wisdom teeth” is absolutely normal. In some people, they erupt by the age of 24-26 and require removal due to growth at the wrong angle, while in others they do not appear at all.
Upper molars
As the anatomy of the upper and lower jaw shows, the most complex morphological units of the human dentition are the molars. They are located in the dental arch behind the small molars. There are 6 molars on the upper jaw - 3 teeth on one side and the other. Experts distinguish between the first, second and third molars.
The largest tooth among the large molars is the first upper molar. He is triangular. The surface of the molar, facing the teeth of the opposite row, may be square or diamond-shaped in shape. It has 4 tubercles (all of the following elevations are separated by grooves):
- distal-palatal;
- disto-buccal;
- media-buccal;
- medial-palatal.
The second upper molar differs from the first one in its chewing surface. On it, 30-40% of people have 3 tubercles. In 5% of cases, a two-cusp upper molar occurs. A tooth usually has 3 roots. Sometimes 2 of them grow together.
The third upper molar has the shortest crown. The chewing surface may be tri-tubercular. In some people, this tooth has 4 cusps. The bicuspid form is extremely rare. A molar may have2, and 3 roots. Sometimes they coalesce.
Lower molars
The difference between the lower large molars from the upper is primarily in the shape of the crown. It can be rectangular or pentagonal. Another distinguishing feature of the lower molars from the upper ones is the number of roots. The bone formations located below have 2 roots.
The anatomy of the mandibular molars is as follows:
- The first molar has distal, distal-lingual, distal-buccal, mesial-lingual, and mesial-buccal cusps.
- The next large molar does not have a distal cusp. The crown has a four-cusp appearance.
- The third molar, which is the smallest of the large molars of the lower jaw, has 4 cusps in 50% of people, 5 in 40%. A three- or six-cusp chewing surface is much less common.
Upper incisors
Bone formations located in front of the upper jaw and having one root are called upper incisors. Normally, there should be 4 teeth - 2 central and 2 lateral. However, more and more doctors are faced with primary adentia (absence) of the upper lateral incisors. In ancient times, people ate solid food. Both central and lateral incisors took part in biting off food. Nowadays, people eat softer foods. Now the power of the central incisors is enough to bite off food. Lateral teeth carry minimal load. In this regard, their reduction is observed.
The crown of the central incisors is wide. In the medio-distal direction, its width is approximately 8–9 mm. Regarding the vestibular surface, it is worth noting that in the upper incisors it is different. Anatomy of the lower jaw and upper dentition indicates that:
- Central upper teeth may be rectangular, triangular;
- some people have barrel-shaped upper incisors;
- Upper side teeth tend to be triangular or barrel shaped.
The palatal surface of the upper incisors can be flat, evenly concave, spatulate (scoop-shaped). Its appearance depends on the degree of development of the medial and distal marginal ridges, stretching from the base of the crown to the corners of the cutting edge of the teeth. The cutting edge of worn incisors has bends - teeth and tubercles. This waviness disappears as the teeth function in the mouth.
Lower incisors
The smallest teeth in the oral cavity, as shown by the topographic anatomy of the lower jaw, are the lower incisors. They are significantly inferior in size to the incisors located in the upper dentition. This is due to the fact that in the process of biting food, the lower teeth perform auxiliary functions.
There are 4 incisors on the lower jaw - 2 central and 2 lateral. The central teeth may have an ovoid or rectangular vestibular surface. At the lateral incisors, it has the form of an isosceles triangle, havingthe base at the incisal edge and the apex where the neck of the tooth is located.
The lingual surface of the lower incisors is smooth, concave. The shape is triangular. Along the edges of the lingual surface of the lower teeth are the distal and medial marginal ridges. They are less developed than on the upper incisors. In newly erupted teeth, the incisal edge is tortuous. The bumps are clearly visible. Gradually they disappear. The incisal edge becomes even.
Upper fangs
Topographic anatomy of the teeth of the upper and lower jaws includes the study of the structure of the canines. These are large bone formations of the dentoalveolar system, having one powerful and long root and a single tubercle crown. This structure of the upper teeth is due to the functions they perform.
Upper canines are located in places where the upper dental arch curves from front to back. The vestibular surface of the crown has a rhomboid shape. A median roller, also called the central mamelon, passes through it. In some people, it is clearly visible, while in others it is barely expressed. The median roller ends with a tearing tubercle, which is a distinctive feature of the fangs. Along the edges of the crown, there are also lateral mamelons - medial and distal. They form the side faces of the tubercle.
The palatal surface of the canines is slightly convex and embossed. A small tubercle is visible in the cervical region. A median ridge runs from it towards the main tubercle. On the sides, the distal and medial marginal ridges can be distinguished. They extend from the corners of the crown to the palatine tubercle.
Lower fangs
Morea narrow and elongated crown, less massiveness - the characteristics that distinguish the lower canines from the upper ones. However, the structure of the teeth is similar. If we compare the canines of the lower and upper jaws, we can see that the crown has a diamond shape. Only here, at the lower teeth, the top of the rhombus in the region of the tearing tubercle is more smoothed, truncated.
Most people have a convex canine of the lower jaw. Anatomy explains this by the fact that the median roller, passing along the vestibular surface, is expressed quite well. Lateral ridges are usually less noticeable. However, in some people, the vestibular surface of the teeth has a flattened shape. The median ridge in such cases is less pronounced.
The relief of the lingual surface of the lower canines is quite poor. On it in the cervical region there is a lingual tubercle. It merges smoothly with the main ridge, ending in the middle third of the lingual surface. Marginal ridges are visible along the edges of the crown.
Upper premolars
There are 4 premolars on the upper jaw - 2 small molars on each side. They are located in the middle part of the dental arch, occupying the 4th and 5th positions. Premolars, as evidenced by the anatomy of the teeth of the upper and lower jaws, perform an auxiliary function in the process of mechanical processing of food. They crush and grind the food they eat.
Distinguish between the first and second upper premolars. The first small molar, having a prismatic crown, can be two- or one-rooted. On thechewing surface there are 2 tubercles - buccal and palatine. The first one is usually larger and taller. Between them there is an intertubercular furrow. There are marginal ridges along the edges of the crown.
The second upper premolar has almost the same structure. There are only a few distinguishing characteristics:
- tooth usually has one root canal and one root;
- crown relief is smoother;
- chewing tubercles are almost the same height;
- lateral ridges are underdeveloped.
Lower premolars
The lower molars, unlike the upper ones, are smaller, have a longer single root and a rounded crown in horizontal section. People who know the anatomy of the teeth of the lower jaw distinguish between the first and second lower premolars, which differ slightly in structure.
The first of these bears resemblance to a fang. These teeth have similar crowns. However, a small molar, unlike a canine, has 2 tubercles on the chewing surface. The first of them is called buccal, and the second - lingual. The tubercles are separated by an intertubercular furrow. In many people it is interrupted by the median transverse crest.
The second small molar, as evidenced by the anatomy of the human lower jaw, is slightly larger than the first. The chewing surface is bicuspid. Sometimes 3 and even 4 tubercles are revealed. On the surface of a small molar there is a deep transverse groove withterminal branches. The root of the second premolar is longer than that of the first.
Thus, the teeth that make up the upper and lower jaws, the structure, anatomy of these elements is a complex but interesting topic. Each bone formation is built from special tissues, has its own blood vessels and nervous apparatus. The structure of the teeth is quite complicated, because it depends on the functions they perform.
