Dental prosthetics with fixed bridges is the most common method of treating violations of the integrity of the dentition. The service life of a bridge, according to various authors, is from five to fifteen years, depending on the number of supporting teeth, the presence or absence of periodontal disease, the length of the bridge, etc. In addition, the most important condition is the correct manufacture and fixation of the prosthesis in the oral cavity. In this regard, in modern practical dentistry More and more attention is being paid to the problem of low-crowned teeth prosthetics. There are many options for solving this problem. This includes the use of pin teeth as a support for a bridge prosthesis, increasing the length of the edge of the orthopedic structure, and creating additional retention elements when preparing the tooth crown. Surgical and orthodontic preparation of teeth before prosthetics can be used, aimed at increasing the retention area. However, in practical dentistry, for various reasons, all this is used quite rarely, and if it is used, it is completely without observing any principles and clinical indications. All this once again confirms the ineffectiveness of today's common methods of prosthetics with bridges for teeth with a low crown. Thus, this issue remains relevant and needs additional study.
bridges
low coronal part
1. Arutyunov S.D., Lebedenko I.Yu. Odontopreparation for orthopedic denture designs. – 2007. – 80 p.
2. Verstakov D.V., Salyamov Kh.Yu., Danilina T.F. Features of treating patients with orthopedic structures under the condition of low crowns of supporting teeth // Materials of the All-Russian scientific and practical conference dedicated to the 50th anniversary of the Faculty of Dentistry of Volgograd State Medical University. – Volgograd, 2011. – pp. 348–351.
3. Danilina T.F., Mikhalchenko D.V., Zhidovinov A.V., Poroshin A.V., Khvostov S.N., Virobyan V.A. A method for diagnosing intolerance to orthopedic structures in the oral cavity // Modern science-intensive technologies. – 2013. – No. 1. – P. 46–48.
4. Zhulev E.N., Arutyunov S.D. Design of fixed dentures using inlays. – 2005. – P. 59, 88.
5. Kibkalo A.P., Timacheva T.B., Motorkina T.V., Shemonaev V.I., Mikhalchenko D.V. Generalized results of research by department staff orthopedic dentistry, dedicated to the adaptation of patients to orthopedic dental intervention // Bulletin of the Volgograd State Medical University. – Volgograd, 2003. – No. 9. – P. 177–178.
6. Ryakhovsky A.N., Ukhanov M.M., Karapetyan A.A., Aleinikov K.V. Review of dental preparation methods metal-ceramic crowns// Panorama of orthopedic dentistry. – 2008. – No. 4. – P. 3–13.
7. Trezubov V.N., Emgakhov V.S., Sapronova O.N. Orthopedic treatment using metal-ceramic dentures. – M., 2007. – 200 p.
Dental prosthetics with fixed bridges is the most common method of treating violations of the integrity of the dentition. Such prostheses have a number of advantages:
Restore chewing efficiency by almost 100%;
They have high aesthetic qualities (dentures do not have locks or fastenings, and the color and material of the crown can be selected according to the color that best matches the shade of natural teeth);
Do not interfere with taste, temperature and tactile sensitivity;
Adaptation occurs in a very short time;
The use of modern materials does not cause allergic reactions;
Block the displacement of adjacent teeth towards missing ones;
Durable (the service life of a bridge, according to various authors, is from five to fifteen years, depending on the number of supporting teeth, the presence or absence of periodontal disease, the length of the bridge, and hygienic care of the structure).
The most important condition is the correct manufacture and fixation of the prosthesis in the oral cavity. In this regard, in modern practical dentistry, more and more attention is paid to the problem of prosthetics of teeth with low crowns. The quality of prosthetics will be influenced by many factors. Analysis of long-term results of orthopedic treatment, according to the literature, shows that impaired fixation of fixed bridge structures, including those with low crowns of abutment teeth, is observed in 38% of cases. One of the options for solving this problem could be to use pin teeth as a support for the bridge, but this can be problematic due to the non-parallelism of the root canals. In addition, after endodontic treatment with the use of pin structures, complications in the form of loosening also occur quite often - in 18.94%. In the practice of dentistry, some orthopedists increase the height of the stump of the supporting tooth due to deeper preparation, destroying the dentogingival attachment and circular ligament, or insufficient preparation of the occlusal surface, thereby increasing the height of the bite. The first option is unacceptable. Increasing the length of the edge of the orthopedic structure in this way, without understanding the position of the edge of the orthopedic structure relative to the structural parts of the periodontium, has a detrimental effect on both the condition of the periodontium itself and the result of treatment as a whole. The exception is cases of dentoalveolar advancement, when gingivectomy is performed from the vestibular side for aesthetic reasons. The second option should be used only in cases of uncompensated generalized tooth abrasion, when there is a decrease in the height of the bite. In all other cases, with the exception of rare indications related to the need to correct the bite, this method of ensuring denture retention should be avoided, since it can cause dysfunction of the temporomandibular joint. Despite the obvious advantages of surgical and orthodontic methods for correcting imbalances in the proportions of teeth and improving the fixation of orthopedic structures, they are rarely used in practical dentistry, and if they are used, then without following clinical indications. Most likely, this is due to the traumatic nature of the manipulations, the duration and the lack of a mandatory result.
All this once again confirms the ineffectiveness of today's common methods of prosthetics with bridges for teeth with a low crown. Thus, this issue remains relevant and needs additional study.
The purpose of the study is to evaluate the importance of various factors influencing the quality of low-crown dental prosthetics.
Materials and research methods
An objective examination of 300 patients was carried out: 180 men and 120 women. The data was entered into examination cards compiled in accordance with WHO recommendations, with an assessment of the parameters of the standard sizes of the clinical crown of abutment teeth. Biometrics of models of the crowns of abutment teeth were carried out, 1200 measurements were made using the method of biometric study of diagnostic models of jaws.
During the examination of patients, the “Unified method for assessing the height of the crowns of abutment teeth based on the analysis of an orthopantomogram” was used. Based on the obtained average values, a clinical systematization of the height of the crowns of the abutment teeth of the upper and lower jaws was carried out according to the group affiliation of the teeth. To designate this value, the abutment tooth crown height index (ACHE) was used. A standardized radiopaque measuring template was developed and used, which was attached to the abutment teeth, followed by calibration of the size of the abutment tooth. A quantitative analysis of orthopantomograms was carried out with the drawing of vertical reference lines relative to the standard standard, which made it possible to estimate the size of the clinical crown of the abutment tooth.
The service life of bridges in different groups during repeated prosthetics and the effectiveness of orthopedic treatment were assessed.
Research results and discussion
The success of orthopedic treatment for patients depends on many factors. All factors can be divided into two groups. The first group includes materials and technologies for the manufacture of orthopedic structures, which have undergone revolutionary changes in recent years. The use of new technologies can include the manufacture of structures from metal-free ceramics using zirconium oxide, light-curing composites, and monomer-free plastics. Thanks to the introduction of modern innovations into clinical practice, the effectiveness of orthopedic treatment has increased significantly. Reducing the thickness of crowns (for example, using zirconium oxide) allows for less shortening of the supporting teeth, thereby significantly improving the conditions for fixing dentures. The use of adhesive bridges also reduces the need for unnecessary preparation.
The second group of factors includes conditions for prosthetics in the oral cavity, which are often quite complex. This is due precisely to the anatomical features of the structure of the patient’s maxillofacial area, pathology complicated by deformities or pathological abrasion. The height of the clinical crown of the abutment tooth is one of the criteria for choosing a prosthetic method, as well as materials for prostheses. For long-term functioning of fixed bridges, it is necessary to additionally provide mechanical retention, which is achieved by increasing the adhesion area and introducing additional retention elements. These techniques relate to the concept of macroscopic retention and include the following: parallelism of the walls of the supporting teeth, their height, and the total area of the prepared surface.
To theoretically substantiate these principles, the concepts of “dental engineering” were developed and proposed and two postulates were introduced. According to the first, “the prosthesis is stable only when its movement, when fixed to the supporting crown and on the crown itself, is limited to only one angle of freedom,” that is, the prosthesis is stable when there is only one insertion path. This obliges the doctor to determine the main axis of insertion of the prosthesis and process the walls of the teeth so that they are parallel to this axis. Usually the most vertical axis is taken as a basis standing tooth and prepare it so that the walls of the tooth stump are parallel to this axis.
The second postulate is “the only route of administration should be as long as possible.” Thus, to achieve optimal retention of the structure, a sufficient height of the abutment tooth with maximum parallelism of the walls is necessary.
In practice, we often encounter cases of different sizes of teeth and jaws, including microdentia of the clinical crown of abutment teeth, which is unable to provide adequate retention of the prosthesis. This makes it difficult to manufacture restorative structures, since there is a lack of space in the area of the abutment tooth. It is in this case that it is possible to recommend the use of secondary additional retention factors. These may be grooves, additional cavities, pins. Also, to increase retention, it is very important to maintain the maximum possible diameter of the tooth stump. The concept of “retention” can be divided into macroretention and microretention. The main indicators of macroretention are the total angle of occlusal convergence of the stump walls (total occlusal convergence, defined as the angle of convergence between two opposite lateral surfaces), the height of the stump and the lines of transitions between the walls. Requirements for macroretention have changed significantly recently due to the advent of reinforced glass ionomer and composite cements, which bond much more firmly to the tooth and crown compared to traditional phosphate cement. So, if previously it was believed that the convergence angle should be 5-7 degrees, the minimum stump height should be 5 mm, but now some authors recommend increasing the taper to 10-22 degrees with a stump height of 3 mm. With a normal height of the tooth crown, it is possible to create a larger convergence angle and more rounded lines of transitions between the walls, which will help reduce stress in the frame and provide a tighter fit. However, with a low crown, of course, it is necessary to strengthen macroretention, that is, reduce the angle of convergence, not round off (but smooth out) the transitions between the walls and create additional retention points. The direction of the path of insertion and removal of the structure should be limited to only one option also because it is necessary to obtain a smaller area of cement under conditions of tension and separation. A hyper-beveled stump has many paths along which the tension force can remove the structure. A crown on such a stump will experience many of these forces during operation. Preparation of additional guides parallel to the insertion path enhances retention not only by increasing the total surface area of the cement film, but also because the additional cavities reduce the area of cement subject to tension. Retention is increased by restriction possible ways crown removal to one direction.
If we talk about microretention, then we'll talk about the surface roughness of the side walls of the tooth stump. Regardless of whether the teeth were treated with finishing stones or coarse diamond burs, the fit of the crowns will be the same (no statistically significant differences). The final finishing bur should be a 60 micron diamond grit (red ring). This grain size creates an optimal surface roughness for cement retention. It should be noted that one of the tasks of preparing a tooth for a crown is polishing the ledge. The presence of a smooth and even ledge on the tooth allows you to get an accurate impression and achieve a better marginal fit of the crown. Typically, polishing the ledge is the final step in tooth preparation. However, in the process of polishing the shoulder, the surface of the side walls is often smoothed. A smooth tooth stump will help obtain a more accurate impression. However, before permanent cementation of the crown, the surface must be roughened. There are two methods: the first is intraoral sandblasting. The second method is to treat the side walls with a coarse-grained diamond bur at ultra-low speed with a mechanical or increasing tip. We prefer the second method, since with its help a more pronounced roughness is achieved, and sandblasting can cause injury to the gum tissue.
There are average standards for crown height, root height, and the ratio of root length to crown length, but their use in clinical practice has not been fully implemented, it is necessary to create clinical criteria for assessing the characteristics of the crown of an abutment tooth, to develop principles for treating patients with low crowns of various groups of teeth, including for the use of modern metal-free structures. Clinical systematization of the crown height index of abutment teeth can help to objectively diagnose the condition of the crowns of abutment teeth and differentiate the choice of treatment method to increase the effectiveness of the used fixed denture structures and reliable fixation on the abutment teeth.
Clarification of the average values of the clinical crowns of abutment teeth in combination with an analysis of the magnitude of stresses arising in the abutment teeth under the action of a functional load makes it possible to substantiate the clinical tactics of choosing support elements for fixed orthopedic structures.
1. One of important conditions The reliability of orthopedic structures in the practice of a dentist is the height of the crown of the abutment tooth and the possibility of increasing it through proper preparation, surgical retraction, orthodontic treatment, etc.
2. To increase the area of adhesion of the orthopedic structure to the tooth crown, secondary additional retention elements can be used.
3. Before permanent cementation of the crown, it is necessary to use a diamond bur to create a roughness on the surface of the side walls of the tooth stump, which will significantly affect the retention of the crown.
4. To fix bridges, it is better to use modern materials with good adhesive characteristics.
5. The use of adhesive bridges can improve the quality of orthopedic treatment and service life with a low tooth crown, while the tactics for choosing prosthetic elements will depend on the need to enhance the retention of the orthopedic structure.
6. The use of modern, thinner metal-free structures will significantly reduce the volume of prepared tooth tissue, maintaining the adhesion area and increasing the reliability of prosthetic fixation.
Reviewers:Firsova I.V., Doctor of Medical Sciences, Professor, Head. department therapeutic dentistry VolgSMU, Dental Clinic of VolgSMU, Volgograd;
Mikhalchenko V.F., Doctor of Medical Sciences, Professor of the Department of Therapeutic Dentistry, Dental Clinic of Volgograd State Medical University, Volgograd.
The work was received by the editor on December 5, 2013.
Bibliographic link
Mikhalchenko D.V., Danilina T.F., Verstakov D.V. PROSTHETIC PROSTHETICS FOR TEETH WITH A LOW CROWN WITH FIXED BRIDGES // Basic Research. – 2013. – No. 9-6. – pp. 1066-1069;URL: http://fundamental-research.ru/ru/article/view?id=32897 (access date: 10/20/2019). We bring to your attention magazines published by the publishing house "Academy of Natural Sciences"
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Human teeth are 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; masticatory 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 formations. They form metameric dentition on the jaws, so the area of the jaw with the tooth belonging to it is designated as dentofacial segment. Dentofacial segments are distinguished 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. Uv. 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 various departments. 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
Knowledge of the anatomy, histology, and physiology of the maxillofacial region is necessary to understand those pathological processes, the development and manifestation of which are 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 anatomical and histological structure teeth is necessary and one of the main conditions for becoming a highly qualified dentist.
Anatomy of teeth.
Knowledge of dental anatomy is a necessary condition to solve 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 tooth socket and the adjacent part of the jaw, covered with mucous membrane.
3. Periodontium, the ligamentous apparatus that holds the tooth in the socket.
4. Vessels and nerves.
In other words, the tooth and periodontal tissue are components of the dental
A tooth is divided into a crown part, a neck, a root or roots.
It is customary to distinguish between anatomical and clinical tooth crowns.
An anatomical crown is a part of a tooth covered with enamel.
The clinical crown is the part of the tooth that protrudes above the gum.
With age, the anatomical crown decreases in size as a result of abrasion of the cusps 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 the vestibule of the oral cavity; in the chewing group of teeth it is called buccal;
Oral, facing oral cavity; on the upper jaw it is called palatine, and on the lower jaw it is called lingual;
Contact surfaces of the teeth facing adjacent teeth, and those facing the center of the dentition are mesial, and in the opposite direction are distal;
Chewing, as well as the chewing or cutting edge (in 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, nutritional function for the tooth, a plastic, that is, dentin-forming, and also protective functions.
The tooth cavity has a different shape, depending on the type of tooth it belongs to. The shape of the tooth cavity is close to the shape of the crown part and continues in the root in the form of a canal.
Tooth enamel.
The enamel of the tooth covers the crown, forming a cover that is quite strong and resistant to abrasion. The thickness of the enamel layer is not the same in different parts of the crown. The greatest thickness is observed in the area of the chewing tubercles.
Enamel is the hardest tissue of the body. The hardness of the enamel decreases towards the enamel-dentin border. Hardness is due to the high, up to 96.5 - 97%, content of mineral salts, up to 90% of which is calcium phosphate, that is, hydroxyapatite. About 4% are: calcium carbonate, that is, calcium carbonate, calcium fluoride, magnesium phosphate. 3 – 4% accounts for organic matter.
The 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. Spiraling, in different directions, they pass to the surface of the tooth crown from the enamel-dentin border. By means of an interprismatic substance, an organic substance, the enamel prisms are glued together. The direction of the prisms located closer to the tooth surface is radial. Gunther-Schröder stripes, determined on a longitudinal section, are the result of the radial movement of convoluted prisms. The Retzius lines or stripes on longitudinal sections run more vertically than the Gunther-Schröder stripes and intersect them at right angles. On transverse sections they have the shape of concentric circles. The most numerous and short lines of Retzius are found in the enamel covering the lateral surfaces of the coronal 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 area of the chewing 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 (nasmite shell).
Dentine– the main tissue of the tooth, consists of a main substance impregnated with lime salts and a large number of tubules. It is similar to bone tissue, but is 5–6 times harder. Dentin surrounds the tooth cavity and root canals. The main substance of dentin includes collagen fibers and the substance connecting them. Dentin contains 70–72% mineral salts and organic substances, fat, and water. Peripulpal lentin or predentin is a zone of constant, unceasing dentin growth. Growth increases significantly with pathological abrasion, as well as as a result of odontopreparation. This dentin is called replacement or irregular dentin. Dentin is nourished through Toms fibers, which closer to the tooth surface acquire a direction perpendicular to the dentinal tubules. This outer layer is called mantle dentin. At the border with the enamel, dentin has many projections that penetrate deeply into the enamel. Dentin tubules with processes of odontoblasts partially extend into the enamel.
Cementum covers the outside of the root dentin. Its structure resembles coarse-fibered bone. By chemical composition similar to dentin, but contains only 60% inorganic substances and more organic substances than dentin contains. There are primary and secondary cement. Cementum is firmly connected to dentin through collagen fibers passing into it. It consists of a basic substance, permeated with collagen fibers running in different directions. Cellular elements are located only at the apices 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. Dentin nutrition is diffuse in nature and comes from the periodontium.
The teeth are held in the socket by the ligamentous apparatus - periodontal,
which, in turn, is part of tissues periodontal(gingival mucosa, cementum of tooth roots, periodontium, jaw bone tissue).
We will look at the anatomical shape of the crown parts of teeth. practical exercises using phantoms, which will make it more informative and facilitate the assimilation of the material.
Let's look at other distinctive features of the teeth of the upper and lower jaws.
Features of the anatomical structure of groups of teeth in the upper and lower jaws.
Upper anterior teeth. (It should be noted that some authors argue that the term "anterior group of teeth" is a misnomer.)
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 direct root and 1 channel. The greatest expansion of the cavity is observed at the level of the tooth neck. The axis of the tooth runs along the cutting edge.
Lateral incisors of the maxilla.
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.
Canines of the upper jaw.
The average canine length is 27 mm (24 – 29.7 mm). This is the longest tooth. A canine 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.
First premolars of the maxilla.
The average length of the first premolar is 21 mm (19 – 23 mm). There are different variations in the number of roots and canals of these teeth:
2 roots and 2 canals, with this variation accounting for 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 root bending is observed in 37% of cases. The tooth cavity passes
in the bucco-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 mouths of the canals are funnel-shaped, which ensures free entry into the canal or canals when the tooth cavity is properly opened.
Maxillary second premolars.
The average length of the second premolar is 22 mm (20 – 24 mm).
75% of this group of teeth have 1 root and 1 canal.
2 roots and 2 channels – 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 orifices, and the canals are connected and open with one apical foramen. Two holes are observed in 25% of this group of teeth, according to studies by a number of authors. The tooth cavity is located at the level of the neck, the canal has a slit-like shape.
Molars.
First molars of the maxilla.
The average length of the first molar is 22 mm (20 – 24 mm). It should be noted that the palatal root is in most cases longer, and the distal root 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 there are 2 channels - in the buccal-mesial direction. The tooth cavity resembles a rounded quadrangle in shape and is larger in the bucco-palatal direction. The slightly convex bottom of the tooth cavity is located at the level of the neck. The mouths of the canals are located in the middle of the corresponding roots in the form of minor extensions. The orifice of the fourth additional canal, if present, is located along the line that connects the orifices of the anterior buccal and palatine canals. The mouth of the palatine canal is easily determined, but the rest are difficult to determine, 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 and walls of the cavity to a lesser extent.
Maxillary second molars.
The average length of the maxillary second molars 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. Possibly also fusion of roots.
Maxillary third molars.
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 during autopsy.
Frontal 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 in one hole. Most often, the root is straight, but in 20% of cases it may have a curvature towards the distal or labial side. The canal is narrow, its largest size is in the labio-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 there are 2 canals and 2 roots. In 13% of cases there are 2 converging channels ending in one hole.
A peculiarity of the mandibular incisors is the fact that on radiographs the canals overlap each other and, as a result, are often not identified.
Canines 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 channel, but in 6% of cases there may be 2 channels. 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, the presence of 2 converging canals is noted. In 19.5% of cases, 2 roots and 2 canals are noted. The largest size of the tooth cavity 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.
Mandibular second premolars.
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.
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 has an oval shape and is well passable. In 38% of cases there are 2 channels. There are 2 canals in the mesial root, but in 40–45% of cases they open with one hole. Tooth cavity largest dimensions has a 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 an apex at the distal root, although the tooth cavity has the shape of a rounded quadrangle. The mesial canals are narrower, especially the anterior buccal, which creates difficulties for treatment, especially in elderly patients. In some cases, the branches of the root canals form a dense network.
Mandibular second molars.
The average length of these teeth is 21 mm (19 – 23 mm). They usually have 2 roots and 3 canals. In the mesial root, the canals may merge at its apex. This is observed in 49% of cases. The mesial root is clearly curved in the distal direction in 84% of cases, and the distal root is straight in 74% of cases. There is evidence of the fusion of mesial and distal roots. This anatomical variation is observed in 8% of cases. The tooth cavity has the shape of a rounded quadrangle and is located in the center.
Mandibular third molars.
Their average length is 19 mm (16 – 20 mm). The shape of the crown of these teeth, like the anatomy of the roots, is unpredictable. There may be many roots and canals that are short and crooked.
Based on the general characteristics of the teeth, their belonging to a certain side of the jaw is determined. The main three signs are:
A sign of crown angle, expressed as a greater acuteness of the angle between the cutting edge or chewing surface and the mesial surface compared to another angle between the cutting edge or chewing 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 to the distal edge;
A sign of root position, characterized by deviation of the root distal to the longitudinal axis of the coronal part of the tooth.
Dental formula.
The dental formula is a record of the condition dentition,
condition of existing teeth. It notes extracted teeth, the presence of fillings, artificial crowns and teeth. Each tooth has a corresponding digital designation.
The most famous is the Zsigmondy dental formula, which has 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 identity of the tooth is indicated using lines intersected at an angle.
In addition, most dentists currently recognize the World Health Organization dental formula, according to which each tooth is designated by two numbers. In this case, the first number 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 the top, when looking at the patient. Accordingly, in the patient’s oral cavity, numbering begins from the top, from right to left. For example, the upper right second premolar is designated 15.
However, at present, debate continues about the advantages and disadvantages of both the first and second formulas.
LECTURE No. 2
(orthopedic section) (slide 1)
The dentofacial 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 posterior joint. Integrative functions of the spinal cord and its organs, reflex arcs.
It is necessary to have an understanding of such concepts as: organ, dentofacial system, dentofacial apparatus (slide 2).
An organ is a phylogenetically formed complex of various tissues, united by development, general structure and function (slide 3).
The dental organ, also represented by several groups of tissues, has a certain shape, structure, function, development, and position in the human body. As already mentioned in the previous lecture on the therapeutic section of propaedeutic dentistry, the dental organ consists (c4) of a tooth, socket and bone tissue of the jaws, covered with a mucous membrane, periodontium, blood vessels and nerves.
To perform a number of specific functions, one organ is not enough. In this regard, existing organ systems are considered. System (c5) is a collection of organs that are similar in their general structure, function, origin and development. The dentofacial system is a single functional system and is formed by the dentition of the upper and lower jaws. The unity and stability of the dental system is determined by the alveolar process of the upper jaw and the alveolar part of the lower jaw, as well as the periodontium.
Apparatus (c6) is a combination of systems and individual organs that function in a similar direction or have a common origin and development.
The chewing-speech apparatus (c7), of which the teeth are part, is a complex of interconnected and interacting systems and individual organs involved 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 designed for grasping, promoting food, forming a bolus of food, for swallowing, as well as the sound-speech system, which in turn includes:
b) cheeks with facial 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
interconnected directions: 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 living nature in general and, in particular, in the human dental system under 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 dental system.
Phylogenetically, changes in the form and function of the masticatory organ in various groups of the animal world formed during the development of the species due to the characteristics of living conditions, type of nutrition, etc.
Ontogenetically, during the development of an individual, the dentofacial system undergoes a number of fundamental morphological transformations, in turn, functional changes. In different age periods During the development and life of a person, the structure (shape) of the dental system is different, and is in accordance with the function performed in the corresponding period of life.
It is advisable to note the main stages of development of the dentofacial 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 when receiving breast milk.
Primary occlusion - with a reduced number of teeth, is adapted for a quantitatively reduced load, but provides the intake of food necessary to replenish the energy expenditure of a growing organism.
Changeable bite – due to wear or complete loss of individual groups of baby teeth, before the complete eruption of permanent teeth, the child’s chewing ability decreases.
Permanent bite – has the greatest ability to perform the 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 eat a normal diet of nutritious natural food. For this, it is necessary to have a normal state of the dental system with a healthy permanent bite.
Anatomical and functional state of the oral cavity in old age occupies a special position in the ontogenetic development of the dental system. In old age, in addition to the loss of individual teeth, groups of teeth or complete loss of teeth, the condition of the alveolar process of the upper jaw and the alveolar part of the lower jaw also changes, or more correctly, the condition of the alveolar ridges, the oral mucosa, the tone of the facial and masticatory muscles, etc. d.
We looked at the clinical anatomy of teeth in a lecture on therapeutic dentistry, so today we will look at clinical anatomy dentition. upper and lower jaws, temporomandibular joint, chewing and facial 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- This is a figurative concept. In this regard, the term “dental arch” is often used (p12).
Dental arch- this is an imaginary curve passing along the cutting edge and the middle of the chewing surface of the dentition (p13).
In addition to the dental arch, prosthetic dentistry distinguishes between the alveolar and basal (apical) arches.
Alveolar arch 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 base (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 turbinates. The unpaired bones are the vomer and hyoid bone.
Human teeth are an integral part of the masticatory-speech apparatus, which is a complex of interacting and interconnected organs that take part in chewing, breathing, and the formation of voice and speech.
This complex includes: 1) solid support - the facial skeleton and the temporomandibular joint; 2) chewing muscles; 3) organs designed to capture, promote food and form a bolus of food 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 structures. They form metameric dentition on the jaws, therefore the area of the jaw with the tooth belonging to it is designated as the dentofacial segment. Dentofacial segments of both the upper and lower jaws are distinguished.
The dentofacial segment includes: 1) tooth; 2) the dental alveolus and the part of the jaw adjacent to it, covered with mucous membrane; 3) ligamentous apparatus that fixes the tooth to the alveolus; 4) vessels and nerves (Fig. 44).
Teeth are hard (5-6 hardness units on the MOOC scale) organs that serve for the primary mechanical processing of food. On the one hand, this is necessary for its safe movement into 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 are of various shapes, located in special cells of the jaws; teeth are replaced, as a rule, once in a lifetime. First, milk (temporary) teeth function, which appear completely (20 teeth) by the age of 2 years, and then are replaced by permanent teeth (32 teeth).
Parts of the tooth.
Each tooth consists of a crown - a thickened part protruding from the jaw alveolus; neck - the narrowed part adjacent to the crown, and root - the part of the tooth lying inside the alveolus of the jaw. The root ends at the apex 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 refers not to 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 gum atrophy, and the clinical root decreases (Fig. 45).
Inside the tooth there is a small tooth cavity, the shape of which varies in different teeth. In the crown of a tooth, the shape of its cavity almost repeats the shape of the crown. Then it continues into the root in the form of a root canal, which ends at the apex 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 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 closure surface of which there are chewing tubercles, corresponding depressions filled with pulp horns are noticeable in the arch. 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 with dental pulp - a special structure of loose connective tissue rich in cellular elements, blood vessels and nerves. According to the parts of the tooth cavity, the pulp of the crown and the root are distinguished.
General structure of the tooth. 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 tooth enamel, and the dentin of the root is covered with cement.
In the area of the tooth neck, four types of enamel-cement junction can be distinguished:
a) enamel covers cement;
b) cement covers the enamel;
c) enamel and cement are connected end-to-end;
d) an open area of dentin remains between the enamel and cement.
The enamel of intact teeth is covered by a strong, lime-free enamel cuticle. 
Dentin is similar in structure to coarse-fibered bone and differs from it in the absence of cells and great hardness. Dentin consists of cell processes - odontoblasts, which are located in peripheral parts dental pulp and ground substance. It contains a very large number of dentinal tubules in which the processes of odontoblasts pass.
The main substance of dentin, lying between the tubules, consists of collagen fibers and their adhesive substance. There are two layers of dentin: the outer - mantle and the inner - peripulpar. The innermost layer of peripulpal dentin is uncalcified and is called the dentinogenic zone (predentin). This zone is the site of constant dentin growth.
The enamel covering the dentin of the tooth crown consists of enamel prisms - thin (3-6 microns) elongated formations that run in waves through the entire thickness of the enamel and the interprismatic substance that glues them together. 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 coarse-fibrous bone, 70% saturated with salts; collagen fibers in it run in different directions. There are no 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 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 alveolus and cement and is called periodontium (Fig. 47). 
The set of formations surrounding the tooth root: periodontium, alveolus, the corresponding section of the alveolar process and the gum covering it are called periodontium.
The structure of the periodontium. Fixation of the tooth, as noted, is carried out using periodontal tissue, 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 fissure ranges from 0.1 to 0.55 mm. The direction of the bundles of collagen fibers of the periodontium is not the same in its various parts. 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).
Dental fibers begin from the cementum of the root at the bottom of the gingival pocket and spread fan-shaped outward 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 bundles maintains the continuity of the dentition and participates in the distribution of chewing pressure within the dental arch. 
Dentoalveolar fibers start from the cementum of the root along the entire length and go to the wall of the dental alveolus. Bundles of fibers begin at the apex of the root, spread almost vertically, in the 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 bundles of periodontal collagen fibers, as well as the structure of the spongy substance of the jaws, is formed under the influence of 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 more loose.
Tooth surface. For the convenience of describing the relief or localization of pathological processes, a conventional designation of the surfaces of the tooth crown has been adopted. There are five such surfaces (Fig. 49).
1. The closure 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 front teeth, which are in contact with the lips, this surface can be called labial, and in the back teeth, adjacent to the cheek, this surface can be called buccal. 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 side of the vestibule of the mouth, is designated as the vestibular wall of the alveolus.
3. The lingual surface faces the oral cavity towards the tongue. For upper teeth the name palatal surface is applicable. The surfaces of the root and walls of the alveoli directed into the oral cavity 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 one. Similar terms are used to refer to the roots of teeth and the corresponding parts of the alveoli.
Terms denoting directions in relation to the tooth are also common: 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 its vestibular surface faces the researcher.
The crown and root of the tooth are usually divided into thirds. Thus, when dividing a tooth by horizontal planes, the occlusal, middle and cervical thirds are distinguished in the crown, and the cervical, middle and apical thirds in the root. The sagittal planes divide the crown into the medial, middle and distal thirds, and the frontal planes into the vestibular, middle and lingual thirds.
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. When the jaws are closed, the teeth of the upper and lower dental arches are in certain relationships with each other. Thus, the tubercles of the molars and premolars of one jaw correspond to the depressions on the teeth of the same name in the other jaw. In a certain order, opposite incisors and canines come into contact with one another. This ratio of the closed teeth of both dentitions is referred to as occlusion.
The contacting teeth of the upper and lower jaws are called antagonist teeth. As a rule, each tooth has two antagonists - the main and additional ones. The exceptions are the medial lower incisor and the 3rd upper molar, which usually have one antagonist each.
Dental formula. The order of the teeth is recorded in the form of a dental formula, in which individual teeth or groups of teeth are written in numbers or letters and numbers.
The complete dental formula is constructed in such a way that the teeth of each half of the jaws are written in Arabic numerals. This formula for an adult is as follows: 
Individual primary teeth are indicated in the same way.
The order of recording teeth in this formula is as if the recorder is examining the teeth of the person sitting in front of him, which is why this formula is called clinical. When examining patients, clinicians note missing teeth and circle the numbers of the teeth that require treatment. If all the 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 primary dentition is written as follows:
There are group dental formulas that reflect the number of teeth in each group in the halves of the jaws. This formula is called anatomical. In an adult, the group dental formula looks like this: 
Signs of teeth. The teeth of the same name in 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 curvature of the crown enamel;
3) root sign.
The sign of the crown angle is that in the vestibular norm the angle formed by the closure surface and the medial surface is sharper than the angle between the closure surface and the lateral surface of the cutting edge. The last corner is slightly rounded. 
The sign of curvature of the crown enamel is determined by examining the tooth from the side of the closure surface (in the chewing norm), while the medial part of the crown enamel on the vestibular side is more convex than the distal one.
The root sign is determined in the position of the tooth in the vestibular norm. If you 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 apex of the root to the middle of the cutting edge), it turns out that the axis of the tooth is deviated laterally. Consequently, the direction of deviation of the longitudinal axis of the tooth indicates the side of the tooth (Fig. 50).
The concept of dentofacial segments
As noted, the dentofacial segment combines the jaw area and the tooth with the periodontium. The segments of the 1st, 2nd incisors and canines are distinguished; 1st and 2nd premolars; 1st, 2nd and 3rd molars.
The dentofacial segments of the upper and lower jaw include different components (Fig. 51). Thus, the incisive segments of the upper jaw include the alveolar and palatal processes. The dentofacial segments of premolars and molars contain the processes of the upper jaw with the lower wall of the maxillary sinus located in them.
The basis of each segment is the alveolar process (for the upper jaw) or the alveolar part (for the lower jaw). The cross-section of the upper incisal segments in the sagittal plane is close to the triangle. In the area of the premolar and molar-maxillary 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 alveoli is thinner than the inner one, especially in the area of the incisal and canine segments. Palatine process the upper jaw in the incisor-canine segments consists of upper and lower plates, a compact substance and a layer of spongy substance between them, and at the level of the molar-maxillary segments - only of a compact substance or a compact and insignificant amount of spongy substance. The bone beams of the spongy substance are located mainly along the height of the jaw. 
The cross-sectional shape of the incisal segments of the lower jaw in the sagittal plane is close to a triangle, the base of which faces downwards. In the area of the molars, the cross-sections of the segments have the shape of a triangle with the base facing upward. 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. Compact substance outer wall The alveoli have the greatest thickness in the region of the molar-maxillary segments, the smallest in the region of the mental foramen. The thickness of the compact substance of the inner wall of the alveoli is greatest in the region of the canine segments, and least in the region of the molar-maxillary segments. The spongy substance of the lower jaw in its alveolar part consists of straight beams located vertically.
Questions for self-control:
1. What does the human chewing-speech apparatus consist of?
2. What is the dentofacial segment?
3. Describe the general structure of the tooth (parts, surfaces, cavity, hard base).
4. What are the clinical crown and clinical root in dentistry?
5. What is periodontium? Tell us 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 primary teeth according to the World Health Organization (WHO) classification?
9. List the signs of teeth.
10. Tell us about the dental segments of the upper and lower jaws.
An urgent task in orthopedic dentistry is the prosthetics of teeth and dentitions with low clinical crowns, as evidenced by numerous publications. Despite the use of modern technologies in everyday practice for prosthetic treatment of patients with low clinical crowns, the rate of complications remains high. According to studies by domestic and foreign authors, the percentage of complications that arise is up to 15%, the main place being occupied by de-cementation of artificial crowns - 9.1%. The height of the crown part of the tooth can be reduced by the carious process of hard dental tissues, increased abrasion, trauma, the need for significant grinding by the doctor of the occlusal surface of the tooth associated with vertical deformations, excessive preparation and incomplete tooth eruption. 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 with a low crown of the abutment tooth // Journal of scientific articles “Health and Education in the 21st Century”. – M., 2012. - No. 4 – P.329.
2. Dolgalev A. A. Methodology for determining the area of occlusal contacts using software AdobePhotoshop and UniversalDesktopRuler // Dentistry. – 2007. - No. 2 – P. 68-72.
3. Lebedenko I.Yu., Kalivradzhiyan E.S. Orthopedic dentistry. - M: GEOTAR-Media, 2012. - 640 p.
4. Liman A.A. Preparation and prosthetics for patients with low clinical dental crowns: abstract of thesis. dis. ...kan. honey. Sciences: 14.00.21 / A.A. Liman; TGMA. –Tver, 2010. –18 p.
5. Sadykov M.I., Nesterov A.M., Ertesyan A.R. Artificial tooth crown // RF Patent No. 151902, publ. 04/20/2015, Bulletin. No. 11.
6. Dolt A.H., Robbins J.W. Alteredpassiveeruption: Anetiologyofshortclinicalcrowns // QuintessenceInt. – 1997. – Vol.28, No. 6. – P.363-372.
A low clinical crown of an abutment tooth is always a complex and difficult to treat orthopedic case. Despite compliance with all the requirements for tooth preparation, the insufficient area of the stump of the abutment tooth does not guarantee reliable fixation of the artificial crown and fixed bridge prosthesis. The prevalence of patients with low clinical crowns ranges from 12% to 16.7%.
According to the literature, a clinical crown height of less than 5 mm is considered low. Such pathology in the area of molars is 33.4%, premolars 9.1%, and in the frontal group of teeth 6.3%.
Available designs of artificial crowns are often associated with modification of the ledge, covering material, and rarely with methods of preparing an additional cavity on the occlusal surface of the tooth stump. A promising direction solving this problem is to further improve the “classical” design of an artificial crown. Preparation of the optimal shape of the tooth stump with retention elements and taking into account anatomical features specific group of teeth, will improve the reliability of fixation and extend the service life of artificial crowns in patients with low clinical crowns.
Goal: To increase the efficiency of prosthetics of teeth and dentitions of patients with low clinical crowns using a new artificial crown.
Materials and methods. We carried out orthopedic treatment of 17 patients with orthognathic occlusion aged 25-40 years with low clinical dental crowns using an artificial crown of a new design (RF patent No. 151902), 26 crowns of our design were manufactured, including 8 crowns in fixed bridges.
The essence of the new utility model is that the artificial tooth crown contains outer and inner surfaces, has a certain thickness, on the inner surface of the crown there is a monolithic protrusion made of the same material as the crown, the protrusion is located along the longitudinal axis of the tooth. The protrusion has the shape of an inlay, and its end part, facing the roots of the tooth, is made in the form of a hemisphere, and the walls of the inlay are parallel to each other or taper 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 (an option for 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 inlay -4, made in the form of a hemisphere, with the walls of the inlay being parallel or tapering 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 for 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 curved roots (root); impossibility of unsealing root canals for pin structures; with an index of destruction of the occlusal surface of the tooth (IROPD) of 0.6-0.8; to prevent further destruction of hard tooth tissues; pathological abrasion of teeth; trauma to the clinical crown of the tooth; for the location of supporting and fixing elements of bridges and other orthopedic structures.
Fig. 1a,b Diagram and photo of the finished artificial cast metal crown made using our method: 1 - artificial tooth crown; 2 - outside surface; 3 - inner surface; 4 - “tab” inside the crown; 5 - end part of the tab; 6 - tooth root; 7 - place (cavity) for the tooth stump; 8 - occlusal surface of the tooth stump
Contraindications to the use of a new artificial crown: frontal teeth; severe periodontitis; tooth mobility II-III degree using the “Periotest” device; 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 “inlay” -4 are parallel or expand 2-3º to the side the occlusal surface of the tooth relative to its longitudinal axis for the convenience of applying the finished crown to the tooth stump. Then the occlusal surface of the tooth stump -7 is also prepared in the form of a hemisphere -8. The placement of hemispheres on the tooth stump, respectively, and on the artificial crown helps relieve tension in the tissues of the tooth stump and in the crown after it is fixed to the tooth, which reduces the risk of fracture of the tooth crown. The remaining parts of the tooth stump are prepared according to a known method, or a ledge in the form of a quarter of a sphere is formed on the tooth stump 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 (example for a cast metal crown). The finished metal crown is ground, polished and fixed to the patient’s tooth in the oral cavity.
After preparing the supporting teeth for an artificial crown of a new design, using the vital staining method, hard tooth tissues affected by caries were identified. In our work, we used the drug “Caries Marker”, produced by “VOCO”, Germany. In the presence of foci of demineralization (intense red color of varying intensity depending on the degree of damage), the affected tissues were excised to identify healthy areas. 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 figures.
To control the occlusal relationships of the dentition after the manufacture of artificial crowns (bridges), we used the method of determining the area of occlusal contacts according to A.A. Dolgalev (2007). The technique is based on the principle that the amount 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 closure of the dentition. The resulting occlusiogram was scanned to convert it into a digital 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 UniversalDesktopRuler. And thus, the total area of occlusal contacts was obtained. According to A.A. Dolgaleva (2007) the area of closure of the dentition in adults with orthognathic occlusion averages 281 mm2. In our patients, the area of tooth closure after the manufacture of dentures was 275.6 ± 10.3 mm2 (p≤0.05).
The study of the supporting teeth before and after the manufacture of a new artificial crown was carried out using a 3D cone-beam computed tomograph (3D CBCT) PlanmecaProMax 3D Max (Planmeca, Finland). Processing and visualization of scanning data was carried out using the PlanmecaRomexisViewer 3.1.1.R program.
To diagnose the shock-absorbing ability of the periodontium of abutment teeth, the “Periotest” device (company “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 tooth under study at a distance of 0.5-2.5 mm. During the examination, 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 degree I tooth mobility, and the rest had degree 0 mobility.
The patients (17 people) were observed for two years; there were no cases of decementing of crowns and bridges.
As an illustration, we present clinical example. Patient S., 43 years old, came to the clinic with complaints of an aesthetic defect and constant decementing 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-soldered bridge prosthesis supported on teeth 35 and 37.
After removing the stamped-soldered bridge prosthesis, depulping the supporting teeth and choosing a solid metal bridge prosthesis by the patient, it was decided to make a solid cast bridge prosthesis with supporting crowns of our design for teeth 35 and 37, since the height of the tooth stumps before preparation was 4.7 mm and 5 mm, respectively.
The preparation of abutment teeth 35, 37 for a solid-cast bridge with abutment crowns of our design was carried out using a well-known method, and the occlusal surface of the tooth stump and the bottom of the cavity (the place for the “inlay” of an artificial crown) on the occlusal surface of the teeth were prepared in the shape of a hemisphere (Fig. 2a). A ledge in the form of a quarter of a sphere was formed on the tooth stump along the neck of the root. Then a working two-layer silicone impression (Fig. 2b) was taken from the supporting teeth 35, 37 and an alginate impression from the upper jaw.
Fig.2. Abutment teeth 35 and 37 of patient S., 43 years old, prepared (a) under a solid-cast bridge prosthesis with abutment crowns of our design; working two-layer silicone impression (b) from abutment teeth 35 and 37 of patient S.
A one-piece cast bridge prosthesis with supporting crowns of our design was fitted to the supporting teeth 35 and 37. The articulatory relationships 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. 3), which corresponds to the average data for the area of closure of the dentition with orthognathic bite according to A.A. Dolgalev (2007).
Rice. 3. Occlusiogram (a) of patient S., 43 years old, in the Adobe Photoshop window; Selected part of the occlusiogram (b) of patient S. intended for measuring the area using UniversalDesktopRuler
Fig.4. Finished design of a solid-cast bridge prosthesis with supporting crowns of our design by patient S. 43 years old, fixed to abutment teeth 35 and 37
After fixing the solid-cast bridge with supporting crowns of our design, periotestometry of the abutment teeth 35 and 37 was performed to study the damping ability of the periodontium. According to the device, the digital indices for teeth 35 and 37 ranged from -08 to +09, which corresponds to 0 degree of mobility.
Using 3D CBCT, we assessed: the topography of the axis of the “inlay” of the crown in the tooth stump; quality of filling the crown bed with cement; fit of the edge of the artificial crown to the tooth; quality of therapeutic dental treatment before prosthetics. The patient was observed by us for two years after prosthetics; there were no complications.
Conclusion. Thus, the new artificial tooth crown we have developed allows for high-quality prosthetics for patients with low clinical crowns of supporting teeth, increases the convenience of modeling an artificial wax crown on the tooth stump, especially the protrusion, removes the wax crown from the tooth without deformation and simplifies the application of the finished artificial crown on tooth. In addition, the crown evenly distributes chewing pressure on the stump and root(s) of the tooth, and, as a result, the risk of fracture of the clinical crown of the tooth is reduced. The data from 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 Budgetary Educational Institution of Higher Professional Education medical University» Ministry of Health 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 AN ORTHOPEDIC DENTISTRY CLINIC FOR LOW CLINICAL CROWNS // Contemporary issues science and education. – 2015. – No. 3.;URL: http://site/ru/article/view?id=19888 (access date: 10/20/2019).
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