The most important organs of the human body include teeth. 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? We have to figure out these and other issues related to the structure of teeth.
General information about teeth
An adult in the oral cavity can normally have from 28 to 32 teeth. They are special formations with a complex structure. The visible part of each tooth is called a crown. One of its layers is dentin - a solid calcified material that does not have blood vessels. Top it is covered with tooth enamel. It serves as an external protective shell.
The hidden part of the tooth is the root. It is placed in the deepening of the jawbone, called the alveoli. There is dentin in the root too. 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, blood vessels and soft connective tissue.
Types and functions of teeth
The anatomy of the lower jaw and upper jaw divides the bone formations located in the oral cavity into several varieties:
- large indigenous (molars);
- front (incisors);
- conical (fangs);
- small indigenous (premolars).
Teeth perform several important functions. Firstly, they provide mechanical processing of food. Thanks to teeth, people can fully eat. Secondly, these bone structures are involved in the formation of speech. With the help of them various sounds are formed. 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 of food. This is facilitated by their flat chisel-shaped crown. Fangs perform the function of crushing and grabbing food, as they have a pointed conical shape. Molars and premolars participate in the grinding of food, because their surface is quite wide.
The location of the teeth on the jaws
The anatomy of the lower jaw and upper dentition shows that bone formations are located in the form of arches, each of which can be divided into 2 sides (quadrant). One quadrant in an adult consists of 8 teeth:
- 3 molars;
- 2 incisors;
- 1 fang
- 2 premolars.
For some people, the last molars in the dentition called “wisdom teeth” are missing. In each quadrant, not 8, but 7 bone formations are obtained. The absence of “wisdom teeth” is an absolutely normal occurrence. In some people, they erupt by the age of 24–26 and require removal due to growth at the wrong angle, while others 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 each on one side and the other. Specialists distinguish the first, second and third large molars.
The largest tooth among large molars is the first upper molar. He is a three-root. The surface of the molar, facing the teeth of the opposite row, in its shape can be square or diamond-shaped. There are 4 tubercles on it (all of the elevations listed below are divided by grooves):
- distal palatine;
- distal buccal;
- medial-buccal;
- medial palatine.
The second upper molar differs from the first by a chewing surface. On it, 30–40% of people have 3 tubercles. In 5% of cases, a two-tubercular superior molar occurs. As a rule, 3 roots are revealed in a tooth. Sometimes 2 of them grow together.
The third upper molar has the shortest crown. The chewing surface may be three-tubercular. In some people, this tooth has 4 tubercles. The two-tuberous form is extremely rare. A molar can have both 2 and 3 roots. Sometimes they grow together.
Lower molars
The difference between the lower large molars and the upper is primarily in the form of a crown. It can be rectangular or pentagonal. Another distinguishing feature of the lower molars from the upper ones is the number of roots. Bone formations located below have 2 roots.
The anatomy of molars of the lower jaw is as follows:
- On the first molar there is a distal, distal lingual, distal buccal, medial lingual and medial buccal tubercles.
- The next large molar does not have a distal tubercle. The four-tubercular appearance is inherent in the crown.
- The third molar, which is the smallest of the lower molars of the lower jaw, has 4 tubercles in 50% of the people, and 5 in the 40%. The three- or six-tubercular 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 face 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. Currently, people eat softer foods. Now, for biting off the food, the strength of the central incisors is enough. Lateral teeth carry a minimal load. In this regard, their reduction is observed.
The crown of the central incisors is wide. In the medial-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. The anatomy of the lower jaw and upper dentition indicates that:
- the central upper teeth can be in the form of a rectangle, a triangle;
- in some people, the appearance of the upper incisors is barrel-shaped;
- the upper lateral teeth, as a rule, are inherent in a triangular or barrel-shaped form.
The palatal surface of the upper incisors can be flat, evenly concave, spade-like (scoop-like). Its appearance depends on the degree of development of the medial and distal marginal ridges extending from the base of the crown to the corners of the cutting edge of the teeth. The cutting edge of the unfinished incisors has bends - denticles and tubercles. This undulation disappears as the teeth function in the oral cavity.
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 because in the process of biting food, the lower teeth perform auxiliary functions.
On the lower jaw there are 4 incisors - 2 central and 2 lateral. Central teeth may have an ovoid or rectangular vestibular surface. For lateral incisors, it has the appearance of an isosceles triangle having a base in the region of the cutting edge and apex where the neck of the tooth is located.
The lingual surface of the lower incisors is smooth, concave. The shape is triangular. On the edges of the lingual surface of the lower teeth are distal and medial marginal ridges. They are less developed than on the upper incisors. In recently erupted teeth, the incisal edge is sinuous. The tubercles are clearly visible. Gradually they disappear. The cutting edge becomes flat.
Upper fangs
Topographic anatomy of the teeth of the upper and lower jaws includes the study of the structure of fangs. These are large bone formations of the dentition, having one powerful and long root and a single-tuberous crown. This structure of the upper teeth is due to the functions performed by them.
The upper fangs are located in places of bending of the upper dental arch from front to back. The vestibular surface of the crown is inherent in the diamond shape. The median ridge, also called the central mamelon, passes through it. In some people, it is clearly visible, while in others it is barely pronounced. The median ridge ends with a tearing tuber, which is a hallmark of fangs. Lateral mamelons also pass along the edges of the crown - medial and distal. They form the lateral faces of the hillock.
The palatine surface of the fangs is slightly convex and embossed. In the cervical region, a small tubercle is noticeable. From it towards the main hillock runs the median ridge. On the sides, distal and medial marginal ridges can be distinguished. They stretch from the corners of the crown to the palatine tubercle.
Lower fangs
A narrower and elongated crown, less massiveness - characteristics that distinguish the lower fangs from the upper. However, the structure of the teeth is similar. If you compare the fangs of the lower and upper jaws, you can see that the crown has a diamond shape. Only in the lower teeth, the top of the rhombus in the area of the tearing tubercle is more smooth, truncated.
Most people have a convex fang of the lower jaw. This explains the anatomy by the fact that the median ridge passing along the vestibular surface is quite well expressed. Side rollers are generally less visible. However, in some people, the vestibular surface of the teeth has a flattened shape. The median roller in such cases is less pronounced.
The relief of the lingual surface of the lower canines is rather scarce. On it in the cervical region there is a lingual tubercle. It merges smoothly with the main crest ending in the middle third of the lingual surface. Along the edges of the crown, marginal ridges are noticeable.
Upper premolar
On the upper jaw, a person has 4 premolars - 2 small molars on each side. They are located in the middle of the dental arch, occupying the 4th and 5th positions. Premolars, as evidenced by the anatomy of the teeth of the upper and lower jaw, perform an auxiliary function in the process of mechanical processing of food. They crush and chop the food they eat.
Distinguish the first and second upper premolar. The first molar tooth having a prismatic crown may be two- or single-root. On the chewing surface there are 2 tubercles - buccal and palatine. The first one is usually larger and taller. An inter-tubercular groove passes between them. Along the edges of the crown there are marginal ridges.
The second upper premolar has almost the same structure. Only a few distinguishing characteristics can be distinguished:
- a tooth, as a rule, has one root canal and one root;
- crown relief is smoother;
- chewing tubercles have almost the same height;
- lateral ridges are underdeveloped.
Lower premolar
The lower small 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 premolar, slightly differing in structure.
The first one resembles a fang. These teeth have similar crowns. However, the small molar tooth, unlike the canine, has 2 tubercles on the chewing surface. The first of them is called buccal, and the second - lingual. The tubercles are divided by the inter-tubercle groove. For many people, it is interrupted by a median transverse crest.
The second small molar tooth, as evidenced by the anatomy of the lower jaw of a person, is slightly larger than the first. The chewing surface is double-tubercular. Sometimes 3 and even 4 tubercles come to light. On the surface of the small molar tooth there is a deep transverse groove with end branches. The root of the second premolar is longer than that of the first.
Thus, the teeth that make up the upper and lower jaw, the structure, and the anatomy of these elements are a complex but interesting topic. Each bone formation is built from special tissues, has its own blood vessels and nervous system. The structure of the teeth is rather complicated, because it depends on the functions they perform.