Anatomy, histology of tooth tissues. Anatomical, clinical formula (WHO formula). Determination of tooth belonging: to the upper and lower jaw, crown angle, crown curvature. Tooth structure I According to the amount of crown coverage

Most patients in dental clinics want to have not only a healthy, but also an attractive smile. Unfortunately, not everyone can boast of this.

Back in 1984, some of the components that are necessarily inherent in a “beautiful smile” were identified:

The smile should expose almost 100% of the crown of the tooth and the gingival papillae, while the gingiva itself should not be visible (otherwise, when the gingiva is exposed, we speak of a “gingival smile”).
The gingival contour should be symmetrical, smooth, the edges of the gums at the central incisors and canines should be located at the same level, and at the second incisors - 1-2 mm lower.
The length of the tooth crown should not be less than 11 mm, and the width should correspond to the "golden section".
The gum contour should be in harmony with the smile line.

If the patient's smile does not fit into such standards, then it can be significantly improved by changing the edge of the gingival contour and increasing the length of the dental crown.

What is the lengthening of the clinical crown of the tooth.

Tooth crown lengthening is a tooth-preserving dental intervention, as a result of which the required amount of subgingival tooth tissues is exposed and a new gingival contour is formed.

The cardinal alternative to this manipulation is the removal of the problematic tooth and the installation of an implant of the required length in its place with the formation of the most aesthetic gum contour. But do not forget that not a single most beautiful artificial tooth can be compared in functionality with your real teeth, so it is worth resorting to such a radical method in exceptional cases.

In what cases is it necessary to lengthen the clinical crown of the tooth?

The lengthening of the clinical crown of the tooth can be prescribed to the patient for the following reasons:

aesthetic

"Gum" smile.
Violation of the contour of the gums of one or more teeth.
Too short natural tooth crowns - after eruption, the gum did not rise and remained “lowered” on the tooth.
Under-eruption of one or more teeth in the dentition.
To improve dental hygiene.

Tooth-preserving

The need to restore the length of the teeth, which was lost as a result of pathological abrasion (bruxism, increased tone of the masticatory muscles can lead to this).
The presence of caries in the subgingival part of the tooth, i.e. below the gumline.
The need to carry out and maintain a high-quality restoration of the tooth by any of the methods, because in order to maintain the health of the periodontium, such a restoration should not go below the level of the gums.
For high-quality prosthetics, in case of complete destruction of the tooth crown, for reliable “full” capture of the hard tissues of the tooth and prevention of possible problems with the crown in the future.

periodontal

As one of the components of the complex surgical treatment of periodontal diseases to remove periodontal pockets.

Methods of lengthening the clinical crown of the tooth in modern dentistry

In modern dentistry, there are 4 methods for lengthening the clinical crown of the tooth:

Orthodontic - involves the "stretching" of the tooth from the bone with the help of a bracket system, which can be installed both on several teeth and on the entire jaw. This method is used in the presence of free space between the teeth - antagonists, mainly to lengthen the crown of one "undercut" tooth, the length of which differs from the rest. The disadvantage of this method is the need to wear braces, a long treatment time - 2-3 years, the presence of a retention period.
Surgical - is an operation to remove part of the gum and / or bone and give a new shape to the gum contour. The main types of surgical intervention are gingivectomy or gingivoplasty, as well as bone resection.

This technique is used to "raise" the level of the gum during the correction of the gingival smile, and before caries treatment and restoration, which must be performed below the natural level of the gum.

Orthopedic - involves building up the crown of the tooth with the help of orthopedic structures - veneers / lumineers or dental crowns, due to the installation of which, the bite is raised, i.e. the tooth is elongated from the side of the cutting edge, without involving the gingival zone. This method of lengthening dental crowns is used in the presence of an erased cutting edge and in the restoration of significant defects in destroyed and chipped teeth. Also, the doctor will choose this technique if the patient has short teeth, but at the same time an ideal gingival contour.
The therapeutic method is a composite build-up of the cutting edge. Effective for minor chips and gaps on single teeth.

What does the patient need to know about the lengthening of the clinical crown of the tooth?

In order for the crown lengthening procedure to be successful, it must be carefully and comprehensively planned - this applies to all methods of its implementation. In the planning of such treatment, depending on the chosen method of intervention, several specialists will take part - a periodontist, a dental surgeon and / or an orthodontist, a dentist-therapist and / or an orthopedic dentist.

When planning, to determine the scope and type of intervention, the following are taken into account:

Present and future state of health of periodontal tissues.
The proportions of the tooth itself, the aesthetics of the patient's smile.
The structure of the roots of the tooth and the ratio of the length of the root and crown. It is IMPORTANT that its root part is no less visible.
Condition of the jawbone.
The biological width is the distance from the bottom of the gingival sulcus to the crest of the tooth-bearing bone, and in order for the tooth to subsequently be stable, its value must be at least 3 mm.

Therefore, the lengthening of the clinical crown of the tooth requires a very thorough diagnosis, because. the procedure should not disturb the stability of the teeth on which it will be performed.

The diagnosis before lengthening the crown of the tooth includes:

Assessment of the state of the periodontium (diagnosis by a periodontist).
Diagnosis by a surgeon - if a surgical method of lengthening is supposed.
Consultation and diagnostics with an orthopedist – in case of need for extensive restorations, prosthetics or the use of an orthopedic lengthening method.
Orthodontic consultation and orthodontic diagnostics, if the crown will be lengthened by installing a bracket system

One of the mandatory diagnostic studies will be a 3D CT scan - computed tomography, to determine the length, location of the tooth root and the condition of the jaw bone.

What awaits a patient undergoing a clinical crown lengthening procedure

Read about the orthodontic, orthopedic and therapeutic method of lengthening the crowns of teeth in the relevant sections - on orthodontics (installation of braces), prosthetics with crowns and veneers and restoration. In this article, we will focus on the surgical lengthening of the crown of one, and more often, several anterior teeth.

Basically, in this case, they resort to gingivoplasty - a surgical operation, during which part of the gum is removed along the gingival contour, often this intervention also requires the removal of part of the bone.

This manipulation is performed by a dental surgeon in a surgical office, on an outpatient basis, under local anesthesia and, sometimes, sedation.

Such an operation is prescribed after a thorough diagnosis, in most cases - as a stage of complex treatment and the formation of an aesthetic smile.

Before any surgical intervention, to reduce infection in the oral cavity and speed up healing, professional hygiene and sanitation of the oral cavity is carried out.
The patient is given anesthesia.
After that, if resection (removal) of a part of the bone is required, the mucoperiosteal flap is exfoliated, an osteotomy is performed. A new gingival contour is formed, which is located above the previous one.
The wound is sutured and a gum bandage is applied.
In the postoperative period, for a speedy recovery, the patient is prescribed antiseptic rinses and painkillers, a course of antibiotics may be prescribed. It is necessary to limit the physical and chewing load.
The stitches are removed after about 7-10 days.
Immediately after the wound has healed, temporary restoration or prosthetics is performed, and after a few months, temporary structures are replaced with permanent ones.
Full restoration of the new natural gingival margin occurs in 1-3 years.

Contraindications to the lengthening of the clinical crown of the tooth

In some cases, after weighing all the pros and cons, the dentist may refuse the patient to lengthen the crowns of the teeth.

The reasons for this may be the following:

After the lengthening of the crown of the tooth, the appearance and health of the neighboring teeth will deteriorate.
Regardless of the elongation, the restoration of this tooth is still impossible.
Insufficient biological width.
A tooth with a short crown has a short root.
In orthodontic lengthening, there is no space between the tooth to be lengthened and the opposing tooth.
The ratio of the effort that will be required to lengthen the crown of the tooth and its value is not in favor of saving the tooth.
The patient cannot maintain the required level of periodontal health.

Examples of clinical crown lengthening in our patients

If the veneer protrudes beyond the limits of “its” tooth, it will definitely break.

There is no need to ensure that the entire plane of the veneer is adjacent to the tooth on which it is installed, especially in the area of the cutting edge. Porcelain veneers are a strong enough construction, and they are designed to change the outer surface of the tooth, including increasing the length of the crown. Such prosthetics are reliable, of course, unless you decide to open bottles with your teeth or gnaw on nuts in the shell.

After plastic surgery and raising the gums, it will still “grow” on the teeth in a couple of years.

This is a delusion, after gingivoplasty a new gum contour is formed and then it remains unchanged. This is possible due to the fact that part of the bone tissue is removed, so the gum heals, but does not regenerate and does not return to its original place.

human teeth are an integral part of the masticatory-speech apparatus, and take part in chewing, the formation of voice and speech, as well as in the formation of the contour of the face.

Each tooth has three parts: crown, root and neck. The size and appearance of the crown, as well as the size and number of roots, are related to the type of teeth.

Crown of the tooth- simplistically, this is its upper part. For the interested reader, they share the concepts of the anatomical crown - the part of the tooth covered with enamel, and the clinical crown - this is the part of the tooth that is visible in the mouth and protrudes above the gum. The clinical crown may change during the life of the tooth, such as during eruption or gingival recession.

Tooth root has a conical shape and ends with an apex (apex). The roots of the tooth are located in the dental alveolus. The number of roots in different teeth is not the same. The place where two roots separate is called a bifurcation, and three roots are called a trifurcation.

neck of the tooth- this is the place of transition of the anatomical crown to the root.

Inside the tooth is cavity, which is subdivided into the cavity of the crown and root canal. At the top of the canal there is a small opening through which vessels and nerves pass into the cavity of the tooth containing the pulp.

The wall of the cavity of the tooth, related to its chewing surface, is called vault. In the vault of the cavity there are recesses corresponding to the masticatory tubercles. The bottom of the cavity is the surface from which the root canals. In single-rooted teeth, the bottom of the cavity narrows in a funnel-like manner and passes into the canal, in multi-rooted teeth it is flatter and has holes leading to root canals.

Alveolar bone- bone, the process of the jaw, in which the root of the tooth is located.

Other constituent parts of the tooth are shown in the figure.

Knowledge of the anatomy, histology, physiology of the maxillofacial region is necessary to understand those pathological processes, the development and manifestation of which is directly dependent on the structure and nature of the surrounding organs and tissues.

The approach to the treatment of a particular pathology also depends on the anatomical and physiological characteristics of the organs and tissues in which it occurs.

Knowledge of the anatomical and histological structure of teeth is a necessary and one of the main conditions for the formation of a highly qualified dentist.

Anatomy of teeth.

Knowledge of the anatomy of the tooth is a prerequisite for solving problems of treatment and prevention of its pathological conditions.

The chewing-speech apparatus contains 32 dental organs, 16 each on the upper and

lower jaws.

The dental organ consists of:

2. The hole of the tooth and the part of the jaw adjacent to it, covered with a mucous membrane.

3. Periodontal, ligamentous apparatus that holds the tooth in the hole.

4. Vessels and nerves.

In other words, the tooth and periodontal tissues are components of the dental

In the tooth, the crown, neck, root or roots are distinguished.

It is customary to distinguish between the anatomical and clinical crowns of the tooth.

Anatomical crown is the part of the tooth covered with enamel.

Clinical crown - part of the tooth, protruding above the gum.

With age, the anatomical crown decreases in size as a result of the abrasion of tubercles or cutting edges of the teeth, while the clinical crown, on the contrary, increases due to resorption of the alveolar walls and exposure of the root or roots.

The crown part of the tooth has the following surfaces:

Vestibular, facing towards the vestibule of the oral cavity; in the chewing group of teeth, it is called buccal;

Oral, facing the oral cavity; on the upper jaw it is called the palatine, and on the lower jaw it is called the lingual;

Contact, the surfaces of the teeth facing the neighboring teeth, moreover, facing the center of the dentition - mesial, and in the opposite direction - distal;

Chewing, as well as chewing or cutting edge (at incisors and canines), facing the teeth of the opposite row. This surface should be called occlusal.

Each tooth has a cavity filled with pulp, which distinguishes

crown and root parts. The pulp of the tooth performs a trophic, that is, a nutritional function for the tooth, a plastic, that is, dentine-forming, and also a protective function.

The cavity of the tooth has a different shape, depending on belonging to a particular tooth. The cavity of the tooth is close in shape to the shape of the crown part and continues in the root in the form of a canal.

Tooth enamel.

Tooth enamel covers the crown, forming a sufficiently strong and resistant to abrasion cover. The thickness of the enamel layer is not the same in different parts of the crown. The greatest thickness is noted in the region of masticatory tubercles.

Enamel is the hardest tissue in the body. Enamel hardness decreases towards the enamel-dentine border. The hardness is due to the high, up to 96.5 - 97%, content of mineral salts in it, up to 90% of which are calcium phosphate, that is, hydroxyapatite. About 4% are: calcium carbonate, that is, calcium carbonate, calcium fluoride, magnesium phosphate. 3 - 4% falls on the share of organic substances.

Enamel consists of calcified fibers with rounded surfaces and a groove-like impression on one of them along the entire length of the fiber. These fibers are called enamel prisms. Wriggling spirally, in different directions they pass to the surface of the crown of the tooth from the enamel-dentin border. By means of an interprism substance, an organic substance, the enamel prisms are glued together. The direction of the prisms located closer to the tooth surface is radial. The Gunther-Schroeder stripes, determined on a longitudinal section, are the result of the radial course of the convoluted prisms. Retzius lines or stripes on longitudinal sections run more vertically than Gunter-Schroeder stripes and cross them at a right angle. On transverse sections, they have the shape of concentric circles. The most numerous and short Retzius lines are found in the enamel covering the lateral surfaces of the crown part of the tooth. Towards the chewing surface, they become longer, and some of them, starting at the enamel-dentin border on the lateral surface of the tooth, arc around the region of the masticatory tubercle and end at the enamel-dentin border, but already on the chewing surface of the tooth.

On the very surface of the crowns, the prisms are located parallel to the outer contours of the tooth and merge into a shell - the cuticle (Nasmyth shell).

Dentine- the main tissue of the tooth, consists of the main substance impregnated with lime salts, and a large number of tubules. It resembles bone tissue, but it is 5-6 times harder. Dentin surrounds the cavity of the tooth and root canals. The ground substance of dentin includes collagen fibers and the substance that connects them. Dentin contains 70 - 72% mineral salts and organic matter, fat, water. Peri-pulpal lentin or predentin is a zone of constant, uninterrupted growth of dentin. Growth is significantly enhanced with pathological abrasion, as well as as a result of odontopreparation. Such dentin is called replacement or irregular dentin. The nutrition of dentin occurs through the Toms fibers, which, closer to the surface of the tooth, acquire a direction perpendicular to the dentinal tubules. This outer layer is called mantle dentin. On the border with enamel, dentin has many protrusions that penetrate deep into the enamel. Dentinal tubules with processes of odontoblasts partially pass into the enamel.

The cement covers the outside of the root dentin. In its structure, it resembles a coarse-fibred bone. It is similar in chemical composition to dentin, but contains only 60% of inorganic substances and more than dentin contains - organic. Distinguish between primary and secondary cement. The cement is firmly connected to the dentin by means of collagen fibers passing into it. It consists of the main substance, penetrated by collagen fibers going in different directions. Cellular elements are located only at the tops of the roots and in large numbers - on the surfaces of the roots facing each other. This dentin is secondary. Most of the dentin is acellular and is called primary dentin. Nutrition of the dentin is diffuse in nature and comes from the periodontium.

The teeth are held in the socket by means of a ligamentous apparatus - periodontal,

which, in turn, is part of the tissue periodontal(mucosa of the gums, cement of the roots of the teeth, periodontium, bone tissue of the jaws).

We will consider the anatomical shape of the crown parts of the teeth in practical exercises using phantoms, which will make it possible to achieve greater information content and facilitate the assimilation of the material.

Consider other distinctive features of the teeth of the upper and lower jaws.

Features of the anatomical structure of groups of teeth of the upper and lower jaws.

Anterior teeth of the upper jaw. (It should be noted that some authors argue that the term "frontal group of teeth" is incorrect).

Central incisors of the upper jaw.

The average length of the central incisor is 25 mm (22.5 - 27.5 mm). It always has 1 straight root and 1 channel. The greatest expansion of the cavity is observed at the level of the neck of the tooth. The axis of the tooth runs along the cutting edge.

Lateral incisors of the upper jaw.

The average length of the lateral incisor is 23 mm (21–25 mm). There is always one root and one channel. In most cases, the root has a distal bend.

Fangs of the upper jaw.

The average canine length is 27 mm (24 - 29.7 mm). This is the longest tooth. A fang always has one root and one canal. In most cases (89%), the root is straight, but has a pronounced labial extension. As a result, the root has an oval shape. The apical narrowing is weakly expressed, which makes it difficult to determine the working length of the tooth.

Premolars.

The first premolars of the upper jaw.

The average length of the first premolar is 21 mm (19–23 mm). There are various variations in the number of roots and canals in these teeth:

2 roots and 2 canals, and this variation is 72% of cases;

1 root and 1 canal, in 9% of cases;

1 root and 2 canals, in 13% of cases;

3 roots and 3 canals, in 6% of cases.

Distal bending of the root is observed in 37% of cases. The cavity of the tooth passes

in the buccal-palatal direction and is located deep at the level of the neck of the tooth, that is, covered with a thick layer of dentin. The orifices of the canals are funnel-shaped, which provides free entry into the canal or canals with the correct opening of the tooth cavity.

The second premolars of the upper jaw.

The average length of the second premolar is 22 mm (20 - 24 mm).

1 root and 1 canal have 75% of this group of teeth.

2 roots and 2 canals - 24%.

3 roots and 3 channels - 1%.

It is known that this tooth has 1 root and 1 canal, but, as a rule, there are two mouths, and the canals are connected and opened by one apical opening. Two holes are observed in 25% of this group of teeth, according to studies by several authors. The cavity of the tooth is located at the level of the neck, the channel has a slit-like shape.

Molars.

The first molars of the upper jaw.

The average length of the first molar is 22 mm (20–24 mm). It should be noted that the palatine root is in most cases longer, and the distal one is shorter. It is generally accepted that a tooth has 3 roots and 3 canals. In fact, in 45-56% of cases it has 3 roots and 4 canals, and in 2.4% of cases it has 5 canals. Most often, 2 channels - in the bucco-mesial direction. The cavity of the tooth resembles a rounded quadrangle in shape and has a larger size in the buccal-palatal direction. The slightly convex bottom of the tooth cavity is located at the level of the neck. The mouths of the channels are located in the middle of the corresponding roots in the form of minor extensions. The mouth of the fourth additional canal, if any, is located along the line that connects the mouths of the antero-buccal and palatine canals. The mouth of the palatine canal is easily determined, and the rest with difficulty, especially the additional one. With age, replacement dentin is deposited on the roof of the tooth cavity to a greater extent, and on the bottom, walls of the cavity to a lesser extent.

The second molars of the upper jaw.

The average length of the second molars of the upper jaw is 21 mm (19 - 23 mm).

In 54% of cases, the tooth has 3 roots, and in 46% of cases, 4 roots. In most cases, the roots have a distal curvature. Two canals, usually in the anterior buccal root. Perhaps also the merging of the roots.

Third molars of the upper jaw.

This tooth has a large number of anatomical variations.

Most often there are 3 or more roots and canals. However, 2, and sometimes 1 root and canal can be observed. In this regard, the anatomy of the cavity of this tooth is unpredictable and its features are determined at autopsy.

Anterior teeth of the lower jaw.

Central incisors of the lower jaw.

The average length of the central incisors is 21 mm (19–23 mm). 1 canal and 1 root are present in 70% of cases, 2 canals - in 30% of cases, but in most cases they end with one hole. Most often the root is straight, but in 20% of cases it may have a curvature to the distal or labial side. The canal is narrow, the largest size in the labial-lingual direction.

Lateral incisors of the lower jaw.

The average length is 22 mm (20 - 24 mm). In 57% of cases, the tooth has 1 root and 1 canal. In 30% of cases - 2 canals and 2 roots. In 13% of cases - 2 converging canals ending in one hole.

A feature of the incisors of the lower jaw is the fact that the channels overlap each other on radiographs, and, as a result, are often not detected.

Fangs of the lower jaw.

The average length of the fangs is 26 mm (26.5 - 28.5 mm). Usually they have 1 root and 1 canal, but in 6% of cases there may be 2 canals. Deviation of the root apex to the distal side was noted by researchers in 20% of cases. The channel has an oval shape and is well passable.

Premolars of the lower jaw.

First premolars of the mandible.

The average length of the first premolar corresponds to 22 mm (20 - 24 mm).

A tooth usually has 1 root and 1 canal. In 6.5% of cases, there are 2 converging channels. In 19.5% of cases, 2 roots and 2 canals are noted. The largest size of the cavity of the tooth is observed below the neck. The root canal has an oval shape and ends with a pronounced narrowing. Most often, the root has a distal deviation.

Second premolars of the lower jaw.

The average length is 22 mm (20 - 24 mm). Teeth have 1 root and 1 canal in 86.5% of cases. In 13.5% of cases, there is a variation with 2 roots and 2 canals. The root has a distal deviation in most cases.

The first molars of the mandible.

The average length of the first molars is 22 mm (20–24 mm). In 97.8% they have 2 roots. In 2.2% of cases, there is a variation with 3 roots with a bend in the lower third. The single distal canal is oval and well passable. In 38% of cases, 2 channels occur in it. There are 2 canals in the mesial root, but in 40-45% of cases they open with one opening. The cavity of the tooth has the largest dimensions in the mesial direction and is displaced in the mesial-buccal direction, as a result of which the orifices of the mesial root often do not open (in 78% of cases). The bottom of the cavity is slightly convex, located at the level of the neck of the tooth. The mouths of the canals form an almost isosceles triangle with the apex at the distal root, although the tooth cavity has the shape of a rounded quadrilateral. The mesial canals are narrower, especially the anterior buccal canal, making it difficult to process, especially in elderly patients. In some cases, the branching of the root canals form a dense network.

Second molars of the lower jaw.

The average length of these teeth is 21 mm (19 - 23 mm). They usually have 2 roots and 3 canals. In the mesial root, canals may merge at its apex. This is observed in 49% of cases. The mesial root is pronounced distally curved in 84% of cases, and the distal root is straight in 74% of cases. There is information about the fusion of the mesial and distal roots. This anatomical variation is observed in 8% of cases. The cavity of the tooth has the shape of a rounded quadrilateral and is located in the center.

Third molars of the mandible.

Their average length is 19 mm (16 - 20 mm). The crown shape of these teeth, like the anatomy of the roots, is unpredictable. There may be many roots and canals, short and twisted.

According to the general features of the teeth, their belonging to a certain side of the jaw is determined. The main three features are:

A sign of crown angle, expressed as a sharper angle between the incisal or occlusal surface and the mesial surface compared to another angle between the incisal or occlusal surface and the distal surface of the tooth;

A sign of crown curvature, characterized by a steep curvature of the vestibular surface at the mesial edge and a gentle slope of this curvature towards the distal edge;

A sign of the position of the root, characterized by the deviation of the root distally in relation to the longitudinal axis of the crown part of the tooth.

dental formula.

The dental formula is a record of the state of the dentition,

condition of existing teeth. It marks the removed teeth, the presence of fillings, artificial crowns and teeth. Each tooth has a corresponding digital designation.

Zsigmondy's dental formula is the most famous, having four sectors, quadrants, which determine whether the teeth belong to the upper or lower jaw, as well as to the left or right side of the jaw. The belonging of the tooth is indicated by lines crossed at an angle.

In addition, at present, the dental formula of the World Health Organization is recognized by most dentists, according to which each tooth is indicated by two numbers. In this case, the first digit indicates that the tooth belongs to a certain side of a certain jaw, and the second indicates the tooth itself. Numbering starts from left to right, from top, when looking at the patient. Accordingly, in the patient's mouth, the numbering starts from the top, from right to left. For example, the upper right second premolar is numbered 15.

However, at present, disputes continue about the advantages and disadvantages of both the first and second formulas.

LECTURE #2

(orthopedic section) (slide 1)

Dental system as a single anatomical and functional complex. Morpho-functional characteristics of teeth, dentition, jaw bones, periodontium, TMJ. Masticatory muscles in the formation of the FFS. Integrative functions of the AP and its organs, reflex arcs.

It is necessary to have an idea about such concepts as: organ, dentition, dentition (slide 2).

An organ is a phylogenetically formed complex of various tissues, united by development, common structure and function (slide 3).

The dental organ, also represented by several groups of tissues, has a certain shape, structure, function, development, position in the human body. As already mentioned in the last lecture on the therapeutic section of propaedeutic dentistry, the dental organ consists (c4) of the tooth, socket and jaw bone covered with mucous membranes, periodontium, vessels and nerves.

To perform a number of specific functions, one organ is not enough. In this regard, the existing organ systems are considered. System (c5) is a set of organs similar in their general structure, function, origin and development. The dental system is a single functional system and is formed by the dentition of the upper and lower jaws. The unity and stability of the dentition is determined by the alveolar process of the upper jaw and the alveolar part of the lower jaw, as well as by the periodontium.

Apparatus (c6) is an association of systems and separate organs functioning in a similar direction or having a common origin and development.

The chewing and speech apparatus (c7), of which teeth are a part, is a complex of interconnected and interacting systems and individual organs that take part in chewing, breathing, sound production and speech.

The chewing-speech apparatus consists of (c8):

1. Facial skeleton and temporomandibular joints;

2. Chewing muscles;

3. Organs intended for grasping, promoting food, forming a food bolus, for swallowing, as well as a sound-speech system, in turn, including:

b) cheeks with mimic muscles;

4. Organs for biting, crushing and grinding food, that is, teeth, and its enzymatic processing, that is, salivary glands.

Orthopedic dentistry, as a science, among the main ones, has two

interrelated areas: morphological and physiological. These areas, complementing each other, form a single whole - the foundations of theoretical and clinical-practical orthopedic dentistry, which is expressed in the interdependence of form and function.

The doctrine of the interdependence of form and function in orthodontics was created by A.Ya. Katz.

The concept of the interdependence of form and function is not limited only to its significance in orthodontic treatment, but it is widespread in wildlife in general and, in particular, in the human dentoalveolar system in normal conditions and in various pathological conditions.

Manifestations of the interdependence of form and function can be observed in the phylogenetic and ontogenetic development of the human dentoalveolar system.

Phylogenetically, changes in the shape and function of the masticatory organ in various groups of the animal world were formed during the development of the species due to the peculiarities of living conditions, type of nutrition, etc.

Ontogenetically, in the process of development of an individual, the dentoalveolar system undergoes a number of fundamental morphological transformations, in turn, functional changes. In different age periods of development and life of a person, the structure (shape) of the dentition is different, and is in accordance with the function performed in the corresponding period of life.

It is advisable to note the main stages in the development of the dentoalveolar system (c9).

The mouth of a newborn has soft lips, a gingival membrane, pronounced transverse folds of the palate and a fatty pad of the cheeks. All elements are fully adapted for the act of sucking, while taking breast milk.

Milk bite - with a reduced number of teeth, it is adapted for a quantitatively reduced load, however, it provides food intake necessary to replenish the energy costs of a growing organism.

Replaceable bite - due to wear or complete loss of certain groups of milk teeth, until the permanent teeth erupt completely, the child's chewing ability decreases.

Permanent bite - has the greatest ability to perform chewing function. During this period, a person reaches his sexual, physical and mental maturity. He must engage in useful work, both mental and physical. To ensure normal and effective life, he must normally eat high-grade natural food. For this, a normal state of the dentoalveolar system with a healthy permanent bite is necessary.

The anatomical and functional state of the oral cavity in old age occupies a special position along the line of ontogenetic development of the dentoalveolar system. In old age, in addition to the loss of individual teeth, groups of teeth or complete loss of teeth, the state of the alveolar process of the upper jaw and the alveolar part of the lower jaw also changes, or rather, the state of the alveolar ridges, the oral mucosa, the tone of the mimic and masticatory muscles, etc. d.

We considered the clinical anatomy of teeth at a lecture in the section of therapeutic dentistry, so today we will consider the clinical anatomy of the dentition. upper and lower jaws, temporomandibular joint, chewing and mimic muscles.

I would like to draw your attention to the shape of the dentition of the upper and lower jaws.

The dentition of the upper jaw has the shape of a semi-ellipse (c10).

The dentition of the lower jaw has the shape of a parabola (c11).

dentition is a figurative concept. In this regard, the term "dental arch" is often used (c12).

dental arch- this is an imaginary curve passing along the cutting edge and the middle of the chewing surface of the dentition (c13).

In addition to the dental arch, in orthopedic dentistry, alveolar and basal (apical) arches are distinguished.

Alveolar arch- this is an imaginary line drawn in the middle of the alveolar ridge (c14).

Basal arch- an imaginary curve passing along the tops of the roots of the teeth. It may be called the apical basis (c15).

facial skull () includes three large bones: paired bones of the upper jaw, lower jaw, as well as a number of small bones involved in the formation of the walls of the orbit, nasal cavity, and oral cavity. The paired bones of the facial skull include: zygomatic, nasal, lacrimal, palatine bones and inferior nasal conchas. Unpaired bones - vomer and hyoid bone.

Human teeth are an integral part of the chewing and speech apparatus, which is a complex of interacting and interconnected organs involved in chewing, breathing, voice and speech formation.
This complex includes: 1) a solid support - the facial skeleton and the temporomandibular joint; 2) chewing muscles; 3) organs designed to capture, promote food and form a food bolus for swallowing, as well as the sound-speech apparatus: lips, cheeks, palate, teeth, tongue; 4) organs for crushing and grinding food - teeth; 5) organs that serve to soften food and enzymatically process it - the salivary glands of the oral cavity.
Teeth are surrounded by various anatomical formations. They form metameric dentitions on the jaws, therefore the area of the jaw with the tooth belonging to it is designated as the dento-maxillary segment. Allocate dentoalveolar segments of both the upper and lower jaws.
The dentoalveolar segment includes: 1) tooth; 2) dental alveolus and part of the jaw adjacent to it, covered with a mucous membrane; 3) ligamentous apparatus that fixes the tooth to the alveolus; 4) vessels and nerves (Fig. 44).
Teeth are hard (5-6 units of hardness on the MOC scale) organs that serve for the primary mechanical processing of food. On the one hand, this is necessary for its safe movement to subsequent soft organs, and on the other hand, it increases the surface area of food for the action of digestive juices (enzymes) on it.
Human teeth of various shapes are located in special cells of the jaws, the change of teeth occurs, as a rule, once in a lifetime. Initially, milk (temporary) teeth function, which completely (20 teeth) appear by the age of 2, and then are replaced by permanent teeth (32 teeth).
Parts of a tooth.
Each tooth consists of a crown - a thickened part protruding from the jaw alveolus; the neck - the narrowed part adjacent to the crown, and the root - the part of the tooth lying inside the jaw alveolus. The root ends at the tip of the tooth root. Functionally different teeth have an unequal number of roots - from 1 to 3.
In dentistry, it is customary to distinguish between a clinical crown, which does not mean the entire area of the tooth protruding from the dental alveolus, but only the area protruding above the gum, as well as the clinical root - the area of the tooth located in the alveolus. The clinical crown increases with age due to gingival atrophy, and the clinical root decreases (Fig. 45).
Inside the tooth there is a small cavity of the tooth, the shape of which is different in different teeth. In the crown of the tooth, the shape of its cavity almost repeats the shape of the crown. Further, it continues into the root in the form of a root canal, which ends at the top of the root with a hole. In teeth with 2 and 3 roots, there are 2 or 3 root canals and apical foramina, respectively, but the canals can often branch, bifurcate, and recombine into one. The wall of the cavity of the tooth, adjacent to its occlusion surface, is called the vault. In small and large molars, on the occlusion surface of which there are masticatory tubercles, corresponding depressions filled with pulp horns are visible in the arch. The surface of the cavity, from which the root canals begin, is called the bottom of the cavity. In single-rooted teeth, the bottom of the cavity narrows in a funnel-like manner and passes into the canal. In multi-rooted teeth, the bottom is flatter and has holes for each root.
The cavity of the tooth is filled with dental pulp - a special structure of loose connective tissue, rich in cellular elements, blood vessels and nerves. According to the parts of the cavity of the tooth, the pulp of the crown and root are distinguished.
General structure of the tooth. The hard core of a tooth is dentin, a substance similar in structure to bone. Dentin determines the shape of the tooth. The crown-forming dentin is covered with a layer of white tooth enamel, and the root dentin is covered with cementum.
In the region of the neck of the tooth, four types of enamel-cement bonding can be distinguished:
a) enamel overlaps cement;
b) cement overlaps the enamel;
c) enamel and cement are joined "end-to-end";
d) an open area of dentin remains between the enamel and the cementum.
The enamel of intact teeth is covered with a strong, calcareous enamel cuticle.

Dentin is similar in structure to coarse fibrous bone and differs from it in the absence of cells and high hardness. Dentin consists of processes of cells - odontoblasts, which are located in the peripheral sections of the dental pulp, and the ground substance. It has a very large number of dentinal tubules, in which the processes of odontoblasts pass.
The main substance of dentin, which lies between the tubules, consists of collagen fibers and their adhesive substance. There are two layers of dentin: outer - mantle and inner - peripulpal. The innermost layer of the peripulpal dentin is not calcified and is called the dentinogenic zone (predentin). This zone is the site of permanent dentin growth.
The enamel covering the dentin of the tooth crown consists of enamel prisms - thin (3-6 microns) elongated formations that go in waves through the entire thickness of the enamel and glue them interprismatic substance. 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. 46).

Cement is a coarse-fibered bone, 70% saturated with salts, collagen fibers in it go in different directions. There are no vessels in the cement, it feeds diffusely from the periodontium.
The root of the tooth is attached to the alveolus of the jaw through a large number of 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 alveoli and the cementum and is called the periodontium (Fig. 47).

The totality of the formations surrounding the tooth root: the periodontium, the alveolus, the corresponding section of the alveolar process and the gum covering it, are called the periodontium.
The structure of the periodontium. Fixation of the tooth, as noted, is carried out with the help of periodontium, the fibers of which are stretched between the cement and the bone alveolus. The combination of three elements (osseous dental alveolus, periodontium and cementum) is designated as the supporting apparatus of the tooth.
The width of the periodontal gap ranges from 0.1 to 0.55 mm. The direction of the bundles of periodontal collagen fibers is not the same in its various departments. At the mouth of the dental alveolus (marginal periodontium) in the retaining apparatus, dentogingival, interdental and dentoalveolar groups of fiber bundles can be distinguished (Fig. 48).
Dentogingival fibers start from the root cementum at the bottom of the gingival pocket and spread outwards in a fan-like fashion into the connective tissue of the gums. The thickness of the beams does not exceed 0.1 mm.
Interdental fibers form powerful bundles 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 tooth. This group of beams preserves the continuity of the dentition and participates in the distribution of masticatory pressure within the dental arch.

Dentoalveolar fibers start from the cementum of the root throughout and go to the wall of the dental alveolus. The bundles of fibers begin at the top of the root, spread almost vertically, in the near-apical part - horizontally, in the middle and upper third of the root they go obliquely from bottom to top (see Fig. 48).
The orientation of the bundles of periodontal collagen fibers, as well as the structure of the spongy substance of the jaws, is formed under the influence of the functional load. In teeth devoid of antagonists, over time, the direction of the periodontal bundles from oblique becomes horizontal and even oblique in the opposite direction. The periodontium of non-functioning teeth is looser.
tooth surface. For the convenience of describing the relief or localization of pathological processes, the conventional designation of the surfaces of the tooth crown is adopted. There are five such surfaces (Fig. 49).
1. The occlusion surface faces the teeth of the opposite jaw. They are found in molars and premolars. These surfaces are also called chewing surfaces. The incisors and canines at the ends facing the antagonists have a cutting edge.

2. The vestibular (facial) surface is oriented towards the vestibule of the oral cavity. In the anterior teeth in contact with the lips, this surface can be called the labial, and in the posterior teeth adjacent to the cheek, the buccal surface. The continuation of the tooth surface to the root is designated as the vestibular surface of the root, and the wall of the dental alveolus covering the root from the vestibule of the mouth is designated as the vestibular wall of the alveolus.
3. The lingual surface faces the oral cavity to the tongue. For the upper teeth, the name palatal surface is applicable. The surfaces of the root and the wall of the alveolus, directed into the oral cavity itself, are also called.
4. The contact surface is adjacent to the adjacent tooth. There are two such surfaces: the medial surface, facing the middle of the dental arch, and the distal. Similar terms are used to refer to the roots of teeth and the corresponding parts of the alveoli.
Also common are terms denoting directions in relation to the tooth: medial, distal, vestibular, lingual, occlusal, and apical.
When examining and describing teeth, the following terms are used: vestibular norm, chewing norm, lingual norm, etc. The norm is the position established during the study. For example, the vestibular norm is the position of the tooth, in which it faces the vestibular surface to the researcher.
The crown and root of the tooth are usually divided into thirds. So, when dividing a tooth with horizontal planes, the occlusal, middle and cervical thirds are distinguished in the crown, and the cervical, middle and apical thirds in the root. The crown is divided by the sagittal planes into the medial, middle and distal thirds, and by the frontal planes into the vestibular, middle and lingual thirds.
The dental system as a whole. The protruding parts of the teeth (crowns) are located in the jaws, forming dental arches (or rows) - upper and lower. Both dental arches contain 16 teeth in adults: 4 incisors, 2 canines, 4 small molars, or premolars, and 6 large molars, or molars. The teeth of the upper and lower dental arches, when the jaws are closed, are in certain ratios to each other. So, the tubercles of the molars and premolars of one jaw correspond to the recesses on the teeth of the same name of the other jaw. Opposite incisors and canines touch each other in a certain order. This ratio of closed teeth of both dentitions is referred to as occlusion.
The adjoining teeth of the upper and lower jaws are called antagonistic teeth. As a rule, each tooth has two antagonists - the main and additional. The exceptions are the medial lower incisor and the 3rd upper molar, which usually has one antagonist each.
dental formula. The order of the teeth is fixed in the form of a dental formula, in which individual teeth or their groups are written in numbers or letters and numbers.
The complete formula of the teeth is constructed in such a way that the teeth of each half of the jaws are written in Arabic serial numbers. This adult formula looks like this:

Individual milk teeth are indicated in the same way.
The order of recording the teeth in this formula is as if the writer is examining the teeth of a person sitting in front of him, which is why this formula is called clinical. When examining patients, clinicians note missing teeth and circle the number of teeth that require treatment. If all teeth in a row are preserved, such a row is called complete.

The World Health Organization (WHO) has adopted a complete clinical dental formula for permanent dentition in a different form:

According to the WHO classification, the complete clinical dental formula for milk dentitions is written as follows:

There are group dental formulas that reflect the number of teeth in each group in the halves of the jaws. Such a formula is called anatomical. In an adult, the group dental formula is as follows:

Signs of teeth. The teeth of the same name of the right and left dental arches differ in their structure.
There are three signs by which you can determine whether a tooth belongs to the right or left dental arch:
1) sign of crown angle;
2) a sign of crown enamel curvature;
3) sign of the root.
A sign of the crown angle is that in the vestibular norm, the angle formed by the occlusion surface and the medial surface is sharper than the angle between the occlusion surface and the lateral surface of the cutting edge. The last corner is slightly rounded.

A sign of curvature of the crown enamel is determined when the tooth is viewed from the side of the occlusion surface (in the masticatory norm), while the medial part of the crown enamel on the vestibular side is more convex than the distal one.
The sign of the root is determined in the position of the tooth in the vestibular norm. If we draw the longitudinal axis of the crown (lower the perpendicular from the middle of the cutting edge) and the longitudinal axis of the tooth (from the top of the root to the middle of the cutting edge), it turns out that the axis of the tooth is laterally deviated. Therefore, the direction of deviation of the longitudinal axis of the tooth indicates the side of the tooth (Fig. 50).
The concept of dentoalveolar segments
As noted, the dentoalveolar segment combines the jaw area and the tooth with the periodontium. Allocate segments of the 1st, 2nd incisors, canine; 1st and 2nd premolars; 1st, 2nd and 3rd molars.
Dental segments of the upper and lower jaws include various components (Fig. 51). So, the composition of the incisive segments of the upper jaw includes the alveolar and palatine processes. In the dentoalveolar segments of premolars and molars, processes of the upper jaw with the lower wall of the maxillary sinus located in them are enclosed.
The basis of each of the segments is the alveolar process (for the upper jaw) or the alveolar part (for the lower jaw). The section of the upper incisive segments in the sagittal plane is close to a triangle. In the region of the premolar and molar jaw segments, it is trapezoidal or approaches a rectangle. The outer and inner walls of the alveoli consist of a thin layer of compact substance, between them there is a spongy substance, in the alveolus lies the root of the tooth with periodontium. The outer wall of the alveolus is thinner than the inner one, especially in the area of the incisal and canine segments. The palatine process of the upper jaw in the incisor-canine segments consists of the upper and lower plates, a compact substance and a layer of spongy substance between them, and at the level of the molar-maxillary segments it consists only of a compact substance or a compact and insignificant amount of spongy substance. Bone beams of spongy substance are located mainly along the height of the jaw.

The shape of the section of the incisive segments of the lower jaw in the sagittal plane is close to a triangle, the base of which is turned down. In the region of the molars, the sections of the segments have the shape of a triangle with the base facing upwards. The shape of the premolar segments approaches oval. The thickness of the compact substance of the alveolar part of the lower jaw and alveoli is individually different both in different segments and within each of them. The compact substance of the outer wall of the alveoli has the greatest thickness in the region of the molar segments, the smallest in the region of the mental foramen. The thickness of the compact substance of the inner wall of the alveolus is greatest in the region of the canine segments, and the smallest in the region of the molar segments. The spongy substance of the lower jaw in its alveolar part consists of straight beams arranged vertically.
Questions for self-control:
1. What does the chewing and speech apparatus of a person consist of?
2. What is the dentoalveolar segment?
3. Tell the general structure of the tooth (parts, surfaces, cavity, solid base).
4. What is the clinical crown and clinical root in dentistry?
5. What is periodontium? Tell its structure.
6. What is meant by the term "occlusion"?
7. What dental formulas do you know?
8. What are the dental formulas for permanent and milk teeth according to the classification of the World Health Organization (WHO)?
9. List the signs of teeth.
10. Tell us about the dentoalveolar segments of the upper and lower jaws.

An urgent task of orthopedic dentistry is the prosthetics of teeth and dentitions with low clinical crowns, as evidenced by numerous publications. Despite the use of modern technologies for prosthetics in patients with low clinical crowns in everyday practice, the rate of complications remains high. According to studies of domestic and foreign authors, the percentage of complications that occur is up to 15%, the main place is occupied by decementation of artificial crowns - 9.1%. The height of the crown part of the tooth can be reduced by the carious process of hard tissues of the tooth, increased abrasion, trauma, the need for significant grinding of the occlusal surface of the tooth by the doctor associated with vertical deformations, excessive preparation and incomplete eruption of the tooth Insufficient height of the clinical crown of the tooth can lead to poor-quality prosthetics with single crowns and bridge prostheses.

dental prosthetics

low clinical crowns

artificial tooth crown

1. Verstakov D.V., Kolesova T.V., Dyatlenko K.A. Clinical aspects of odontopreparation under the condition of a low crown of the supporting tooth // Journal of scientific articles "Health and education in the XXI century". - M., 2012. - No. 4 - P. 329.

2. Dolgalev A. A. Method for determining the area of occlusal contacts using software AdobePhotoshop and UniversalDesktopRuler // Dentistry. - 2007. - No. 2 - S. 68-72.

3. Lebedenko I.Yu., Kalivradzhiyan E.S. Orthopedic dentistry. - M: GEOTAR-Media, 2012. - 640s.

4. Liman A.A. Preparation and prosthetics of patients with low clinical crowns of teeth: Ph.D. dis. ...can. honey. Sciences: 14.00.21 / A.A. Estuary; TGMA. -Tver, 2010. -18s.

5. Sadykov M.I., Nesterov A.M., Ertesyan A.R. Artificial tooth crown // RF Patent No. 151902, publ. 04/20/2015, Bull. No. 11.

6. DoltA.H., Robbins J.W. Alteredpassiveeruption: Anetiologyofshortclinicalcrowns // QuintessenceInt. - 1997. - Vol.28, No. 6. - P.363-372.

The low clinical crown of the abutment tooth is always a complex and difficult case for orthopedic treatment. Despite compliance with all the requirements for the preparation of teeth, the insufficient area of the abutment tooth stump does not guarantee reliable fixation of the artificial crown and fixed bridge prosthesis. In terms of prevalence, patients with low clinical crowns range from 12% to 16.7%.

According to the literature, a clinical crown height of less than 5mm is considered low. Such a pathology in the region of the molars is 33.4%, premolars 9.1%, and in the frontal group of teeth 6.3%.

The available designs of artificial crowns are more often associated with the modification of the ledge, the covering material, and rarely with the methods of preparing an additional cavity on the occlusal surface of the tooth stump. A promising direction in solving this problem is the further improvement of the "classical" design of an artificial crown. Preparation of the optimal form of the tooth stump with retention elements and taking into account the anatomical features of a particular group of teeth will improve the reliability of fixation and prolong the service life of artificial crowns in patients with low clinical crowns.

Purpose. To increase the effectiveness of prosthetics of teeth and dentitions in patients with low clinical crowns using a new artificial crown.

Materials and methods. We performed orthopedic treatment of 17 patients with orthognathic occlusion at the age of 25-40 years with low clinical crowns of teeth with an artificial crown of a new design (RF patent No. 151902), 26 crowns of our design were made, including 8 crowns in non-removable bridges.

The essence of the new utility model lies in the fact that the artificial tooth crown contains outer and inner surfaces, has a certain thickness, a monolithic protrusion is made on the inner surface of the crown from the same material as the crown, the protrusion is located along the longitudinal axis of the tooth. The protrusion has the form of a tab, and its end part, facing the tooth roots, is made in the form of a hemisphere, and the walls of the tab are parallel to each other or narrow towards the roots of the teeth at an angle of 2-3º degrees relative to the longitudinal axis of the tooth. The bottom of the cavity in the artificial crown for the occlusal surface of the tooth stump is also made in the form of a hemisphere.

A cast artificial metal crown (a variant of a new crown) of tooth -1 (Fig. 1a, b) consists of: the outer surface -2; inner surface -3; "tabs" -4 inside the crown; the end part -5 of the tab -4, made in the form of a hemisphere, while the walls of the tab are parallel or narrow towards the roots of the tooth -6 at an angle of 2-3º relative to the longitudinal axis of the tooth. The place (cavity) for the tooth stump -7 in the artificial crown -1 for the occlusal surface of the tooth stump is also made in the form of a hemisphere -8. An artificial tooth crown can be made of metal alloys, pure ceramics, for example, using CAD / CAM technology and metal ceramics. Basically, such crowns are made on the lateral group of teeth as single crowns or supports for bridges.

The main indications for the manufacture of a new artificial crown are: restoration of the anatomical shape of premolars and molars with low clinical crowns; obstruction of root canals; strongly twisted roots (root); the impossibility of unsealing root canals for pin structures; with an index of destruction of the occlusal surface of the tooth (IROPZ) 0.6-0.8; to prevent further destruction of hard tissues of the tooth; pathological abrasion of teeth; trauma of the clinical crown of the tooth; for the location of supporting and fixing elements of bridges and other orthopedic structures.

Fig.1a, bScheme and photo of the finished artificial cast metal crown, made according to our method: 1 - artificial tooth crown; 2 - outer surface; 3 - inner surface; 4 - "tab" inside the crown; 5 - end part of the tab; 6 - tooth root; 7 - place (cavity) for the stump of the tooth; 8 - occlusal surface of the tooth stump

Contraindications to the use of a new artificial crown: teeth of the frontal group; severe periodontitis; mobility of teeth II-III degree by the device "Periotest"; pathological processes in the periodontium.

An artificial tooth crown is made and used as follows. After examining the tooth, the tooth stump is prepared (see Fig. 1a,b) -7 so that the bottom of the cavity (place) in the tooth has the shape of a hemisphere, and the walls of the cavity for the “insert” -4 are parallel or expand by 2-3º to the side occlusal surface of the tooth relative to its longitudinal axis for the convenience of applying the finished crown to the stump of the tooth. Then, the occlusal surface of the tooth stump -7 is also prepared in the form of a hemisphere -8. Performing on the stump of the tooth, respectively, and on the artificial crown of the hemispheres helps to relieve stress in the tissues of the stump of the tooth and in the crown after its fixation on the tooth, which reduces the risk of fracture of the tooth crown. The remaining parts of the stump of the tooth are prepared according to a known technique, or a ledge in the form of a quarter of a sphere is formed on the stump of the tooth along the neck of the root in order to obtain a congruent shape (a quarter of a sphere) on an artificial crown (along the edge of the crown). Next, a double impression is taken with silicone material, a model is cast from supergis, a crown is modeled from wax or ashless plastic and replaced with metal (an example for a cast metal crown). The finished metal crown is ground, polished and fixed on the patient's tooth in the oral cavity.

After the preparation of the abutment teeth for an artificial crown of a new design, the vital staining method revealed hard tooth tissues affected by caries. In our work, we used Caries Marker, VOCO, Germany. In the presence of foci of demineralization (a shade of intense red color of varying intensity depending on the degree of damage), the affected tissues of the tooth were excised until healthy zones were identified. To determine the exact degree of demineralization of the hard tissues of the supporting teeth, a 10-color diagnostic scale was used, which makes it possible to reflect the degree of staining in percentages or relative numbers.

To control the occlusal ratios of the dentition after the manufacture of artificial crowns (bridges), we used the method for determining the area of occlusal contacts according to A.A. Dolgalev (2007) . The technique is based on the position that the magnitude of chewing efficiency is directly proportional to the total area of occlusal contacts. It is known that it is the area of occlusal contacts that most objectively reflects the quality of the closure of the dentition. The resulting occlusiogram was scanned for conversion into a digital version of the image. Digital images were edited in Adobe Photoshop to highlight the layer of occlusal contacts, and the total area of the edited image was determined using the UniversalDesktopRuler. And thus, the total area of occlusal contacts was obtained. According to A.A. Dolgaleva (2007), the area of closure of dentition in adults with orthognathic occlusion averages 281 mm2. In our patients, the area of occlusion of teeth after the manufacture of prostheses was 275.6 ± 10.3 mm2 (p≤0.05).

The study of abutment teeth before and after the manufacture of a new artificial crown was carried out on a 3D cone beam computed tomography (3DCBCT) PlanmecaProMax 3D Max (Planmeca, Finland). Scanning data were processed and visualized using the Planmeca RomexisViewer 3.1.1.R software.

For the diagnosis of the shock-absorbing ability of the periodontium of the abutment teeth, the Periotest device (manufactured by Gulden, Germany) was used. When percussing abutment teeth covered with crowns, the tip was placed horizontally and at a right angle to the middle of the vestibular plane of the crown of the examined tooth at a distance of 0.5-2.5 mm. During the study, the dentition should be open. Index values range from -08 to +50. According to the degrees of tooth mobility, the index values are distributed as follows: 0 degree from -08 to +09; I degree from +10 to +19; II degree from +20 to +29; III degree from +30 to +50. Among 17 patients, after the manufacture of fixed dentures (26 teeth), two patients had tooth mobility of the 1st degree, and the rest had 0 degree of mobility.

Patients (17 people) were followed up for two years, there were no cases of decementation of crowns and bridges.

As an illustration, we present a clinical example. Patient S., 43 years old, came to the clinic with complaints of an aesthetic defect and permanent decementation of a bridge prosthesis on two artificial crowns. For pain from all types of irritants in the area of teeth 35 and 37. Six years ago, the patient underwent orthopedic treatment with a stamped-brazed bridge supported by teeth 35 and 37.

After removing the stamped-brazed bridge, depulping the abutment teeth and choosing a solid metal bridge for the patient, it was decided to fabricate a solid bridge with abutment crowns of our design for teeth 35 and 37, since the height of the tooth stump before preparation was 4.7 mm and 5 mm, respectively.

The preparation of abutment teeth 35, 37 for a one-piece cast bridge with abutment crowns of our design was carried out by a well-known method, and the occlusal surface of the tooth stump and the bottom of the cavity (the place for the “insert” of the artificial crown) on the occlusal surface of the teeth were prepared in the form of a hemisphere (Fig. 2a). On the stump of the tooth, a ledge in the form of a quarter of a sphere was formed along the neck of the root. Then a working two-layer silicone impression (Fig. 2b) was obtained from the abutment teeth 35, 37 and an alginate impression from the upper jaw.

Fig.2. Abutment teeth 35 and 37 of patient C.43 years old were prepared (a) for a solid bridge prosthesis with abutment crowns of our design; working two-layer silicone impression (b) from abutment teeth 35 and 37 of patient C.

A one-piece cast bridge prosthesis with abutment crowns of our design was fitted on the abutment teeth 35 and 37. The articulation ratios were checked using articulation paper and the area of occlusal contacts of the teeth of the upper and lower jaws was determined, it was -279 mm2 (Fig. orthognathic bite according to A.A. Dolgalev (2007).

Rice. Fig. 3. Occlusiogram (a) of patient S., 43 years old, in the Adobe Photoshop window; Selected part of the occlusiogram (b) of patient C. intended for measuring the area using the UniversalDesktopRuler

Fig.4. Finished construction of a one-piece cast bridge prosthesis with abutment crowns of our design for a patientpp. 43 years old, fixed on abutment teeth 35 and 37

After fixation of a solid bridge prosthesis with retaining crowns of our design, periotestometry of abutment teeth 35 and 37 was performed to study the damping ability of the periodontium. According to the device, the digital indices for tooth 35 and 37 were in the range from -08 to +09, which corresponds to 0 degrees of mobility.

Using 3D CBCT, we assessed: the topography of the axis of the “insert” of the crown in the stump of the tooth; the quality of filling the bed for the crown with cement; fit of the edge of the artificial crown to the tooth; the quality of therapeutic dental treatment before prosthetics. The patient after prosthetics was observed by us for two years, there were no complications.

Conclusion. Thus, the new artificial tooth crown developed by us allows high-quality prosthetics for patients with low clinical crowns of abutment teeth, increases the convenience of modeling an artificial wax crown on the stump of the tooth, especially the protrusion, removes the wax crown from the tooth without deformation and simplifies the imposition of the finished artificial crown on tooth. In addition, the crown evenly distributes chewing pressure on the stump and root (roots) of the tooth, and, as a result, the risk of fracture of the clinical crown of the tooth is reduced. The data of our objective studies allow us to recommend an artificial crown of a new design for implementation in practical healthcare.

Reviewers:

Khamadeeva A.M., Doctor of Medical Sciences, Professor, Head. Department of Pediatric Dentistry, Samara State Medical University, Ministry of Health of the Russian Federation, Samara;

Potapov V.P., Doctor of Medical Sciences, Associate Professor, Professor of the Department of Orthopedic Dentistry, Samara State Medical University, Ministry of Health of the Russian Federation, Samara.

Bibliographic link

Sadykov M.I., Tlustenko V.P., Ertesyan A.R. APPLICATION OF A NEW ARTIFICIAL CROWN IN THE CLINIC OF ORTHOPEDIC DENTISTRY WITH LOW CLINICAL CROWNS // Modern problems of science and education. - 2015. - No. 3.;
URL: http://site/ru/article/view?id=19888 (date of access: 10/20/2019).

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