Secondary adentia what. Adentia of teeth - a sentence or a nuisance? Methods of treatment of the disease. What is adentia

Partially secondary adentia is a common disease that occurs in 65% of the world's population - this is tooth loss.

This affects the functionality of the jaw, because of this, problems with the gastrointestinal tract may appear.

Also, this is reflected in appearance - a person has complexes, atrophy may develop facial muscles. Adentia occurs in both adults and children.

Classification

Adentia is divided into two types:

Partial secondary adentia. If at the top and mandible missing from 1 to 3 teeth.
Full. If in oral cavity More than 80% of teeth are missing.

Even if one or two teeth are missing in the upper or lower jaw, adjacent teeth begin to move.

This negatively affects their main function - chewing food.

With adentia, the bone tissue of the teeth begins to rapidly deplete, since a colossal load is placed on the remaining teeth.

Partially congenital adentia occurs when more than 10 teeth are missing from the jaw. In 70% of cases, the lateral incisors are lost first. upper jaw, adjacent teeth immediately begin to shift in their place, so biting off solid food brings discomfort.

If the disease progresses and the loss of teeth continues, this means that the process has taken on a multiple form. In this case, if measures are not taken to eliminate and treat the cause, the disease can lead to the loss of all dental units.

Partially secondary adentia is a serious stage of pathology, in which the absence of 5 to 15 dental units in one jaw is diagnosed.

Symptoms of adentia

The general symptoms of any type of adentia are reduced to the complete or partial absence of teeth in the oral cavity. This is the main symptom of the disease. However, there are also indirect signs adentia:

There may be a retraction of the soft tissues of the face, which is characterized by a violation of the symmetry of the facial part.
A large number of wrinkles can form around the oral cavity.
With the loss of more than 50% of the teeth of the oral cavity, atrophy of the muscles of the face is observed.
Dropping corners of the mouth.
Changing the shape of the face.

Missing tooth in one row

Partially secondary adentia can also be accompanied by the formation of an incorrect, deep bite. The teeth begin to actively move in the area of the formed voids, due to which the teeth are elongated. alveolar processes healthy teeth.

Diagnostics

Diagnosing this disease is quite simple.

A dentist can visually assess the picture, name the number of teeth that are missing in both jaws, respectively, determine the type of adentia.

If there is a suspicion of adentia, then the diagnosis should include an x-ray of the oral cavity.

In the picture, the doctor will be able to see all the nuances of interest to him, especially if we are talking about childhood adentia. It is important to note the presence of rudiments permanent teeth and their condition.

When diagnosing, it will be effective to carry out panoramic radiography of the upper and lower jaws. panoramic shot allows you to determine the structure of the teeth, the state of the bone tissue of healthy teeth and the alveolar process.

Diagnostics should be carried out qualified specialist, taking into account the following factors:

The presence of roots that have not been previously removed and at the time of the study they are under the mucous membrane. This pathology dangerous inflammatory processes, so these roots should be disposed of as soon as possible.
The presence of exostoses.
Inflammatory or infectious processes flowing in the oral cavity;
The defeat of the mucous membrane by tumors.

Partial absence of teeth

If one of the above factors was found, then it is necessary to first eliminate it, and then proceed to the diagnostic procedures for adentia and the treatment of the disease.

Diagnosis of adentia allows you to immediately see the severity of the disease, and take measures that will not allow the oral cavity to lose its functionality.

The reasons

One of the main causes of adentia is the abnormal development of the ectodermal germ layer, which is the basis for the formation of tooth buds.

Violations of the endocrine system and poor heredity are two more common factors in the development of primary type adentia.

Partially secondary adentia can develop in a person for the following reasons:

Caries. If not treated carious formations on the early stage over time, this can lead to tooth loss.
Various diseases of the oral cavity that affect the gums, mucous membranes and are not cured in time. For example, periodontitis or periodontal disease can cause adentia.
Diseases internal organs , weakened immunity, which negatively affect the activity of the endocrine system.
Age. The likelihood of tooth loss progresses with age. However, young people are now also seeking help in the treatment of adentia.
Rough mechanical impact on the teeth. This is one of the most common and serious causes. This includes mechanical cleaning performed by an unprofessional specialist, frequent bleaching of teeth with chemical compounds, trauma to the jaw and gums.
Incorrect extraction of milk teeth, because of which the rudiment of a permanent tooth is injured, and it begins to develop abnormally.
hereditary factor.

There are many reasons for the development of adentia, and most of them are indirect.

That is, a person for a long period of time may not notice any deviations in the oral cavity, however, at this time there is a negative effect on the teeth, which in the future may lead to their partial complete loss.

Gum disease and bone loss can result from improper brushing of teeth. If food particles constantly accumulate, plaque forms on the teeth, this can lead to gingivitis. In the absence of treatment, mechanical cleanings and fluoridation, all of which will also lead to tooth loss. Therefore, it is important to always observe oral hygiene and not neglect preventive visits to the dentist.

Not everyone knows that there is such a pathology as. Read about the causes of this disease in the article.

What a periodontist treats and how an examination by a doctor is carried out, we will tell.

Treatment of adentia

Most effective therapy disease today is orthopedic treatment.

The method of treatment is determined by the attending physician on the basis of diagnostic tests, depending on the number of missing teeth in the oral cavity.

Treatment of primary adentia involves the installation of a pre-orthodontic trainer, the patient himself is registered with the dispensary.

If adentia was found in a child, then it is important to give the opportunity permanent teeth properly erupt, and eliminate the risk of any jaw defects.

Dentures for adentia are the only option for restoring missing teeth, and the following methods are used for this purpose:

Prosthetics with the use of ceramic-metal crowns and dental inlays.
Using an adhesive bridge.
Installation of the implant in the places of the formed voids.

Treatment should begin with the restoration of the main function of the oral cavity (chewing food). This is necessary in order to prevent the development of any complications and pathological processes that may occur after implantation against the background of an unprepared oral cavity. Only after all diseases, inflammations are eliminated, the main function of the oral cavity is restored, you can proceed to prosthetics.

Installation of a denture

It begins with the installation of a metal pin into the bone tissue, after which a artificial tooth. The dentist selects a color, a material that will be identical to the natural shade of the tooth enamel.

Prosthetics is effective method treatments, however, are costly. The whole process can take several weeks.

Consequences of adentia

Adentia belongs to one of the most complex and serious dental diseases.

Difficulties are manifested in terms of treatment, and adentia also negatively affects the quality of life.

Complete edentulism can cause speech impairment, it may be difficult to pronounce some sounds, speech becomes slurred.

Difficulties are also manifested in biting and chewing solid food, so you have to consume almost all food in liquid form. Poorly digested pieces of food can cause disruption of the gastrointestinal tract, a deficiency appears in the body useful elements and minerals, which also negatively affects overall health.

In the absence of more than 75% of the teeth in the oral cavity, there is a violation of the functionality of the temporomandibular joint, which can lead to its inflammation.

should not be overlooked and psychological factor. Lack of teeth does not look aesthetically pleasing and brings mass discomfort which can create an imbalance psychological nature. This can lead to low self-esteem, depression and nervous disorders.

Modern methods of implantation make it possible to restore all lost teeth, without any impairment of the functionality of the oral cavity. If you start treating adentia at an early stage, you can achieve effective results.

Disease prevention

Specific measures that would prevent adentia, both in adults and in children, have not yet been developed. However, to maintain oral health, the following recommendations should be followed:

Regularly carry out hygiene procedures of the oral cavity, and do it correctly ( soft brush carry out movements from the bottom up (lower jaw) and from top to bottom (upper jaw), in order to exclude all particles of food between the teeth. Then, in a circular motion, walk over the entire surface of the oral cavity and finally clean the tongue);
During pregnancy, eat foods rich in calcium and potassium. This is necessary, both for the woman herself and for the baby.
Regular visits to the dentist in order to identify any diseases, conduct hygienic cleaning oral cavity. If there is a loss of at least one unit of tooth, it is recommended to short time to install an implant in order to exclude the development possible deviations oral cavity.

Partially secondary adentia is a serious pathology that requires diagnosis and timely treatment through the installation of implants. Regular visits to the dentist, compliance with all hygiene measures will reduce the risk of developing adentia.

Lack of treatment can lead not only to impaired functionality, but also to inflammation of the joints, asymmetry of facial tissues, and deviations in the psychological state.

Partial secondary adentia. classification

Partial loss of teeth is not a disease, but one of the forms of damage to the dentition, i.e. pathological condition, which occurs as a result of a disease - caries, periodontal diseases, etc. Therefore, it can be a diagnosis.

A pathological condition caused by a violation of the continuity of the dentition, i.e., the absence of teeth in the dental system, is called partial secondary edentulous or a defect in the dentition. The reasons for it may be:

1. Violations that occur during the formation of the dentoalveolar system:

– primary partial adentia caused by the absence of teeth;

– improper development of the rudiments of teeth (impacted teeth).

2. Violations caused by the loss of teeth in the formed dentoalveolar system, arising from:

– development of complicated caries;

– development of periodontal diseases;

– surgical interventions on the jaws for osteomelitis, neoplasms;

– injuries of teeth and jaws of various etiologies.

According to the data of N.V. Sirgichev (1983), N.M. Rozhno (1989), M.D. Korol (1991), the number of people who need to restore the functional unity of the dentition after the age of 56 reaches 96%, and , 48.34% (±2.5%) of them - in partial removable plate prosthetics (PRPP).

A variety of variants of dental arch defects necessitated their systematization, which in most cases was carried out according to anatomical and topographic features.

So, E. Kennedi (1942) divides dentition defects into four classes:

I class - bilateral end defect; Class II - unilateral end defect;

Class III - an included defect in the area of chewing teeth; Class IV - a defect in the frontal area of the dentition.

If there are several defects in the dentition belonging to different classes, the dental arch is assigned to a smaller class (O. Applegate, 1954).

V. Yu. Kurlyandsky (1965) divides dentition defects into 3 groups:

- 1st - single or multiple defects of the dentition (dentitions) while maintaining the distal supports;

- 2nd - single or multiple defects in the dentition (dentitions) with the loss of one or both distal supports;

- 3rd - intact dentition, single or multiple defects in them against the background of damage to periodontal tissues.

E. I. Gavrilov (1966) proposed to distinguish the following types of dentition defects:

– end (single and double-sided);

– included (side - one-, two-sided, front);

– combined;

– jaws with singly preserved teeth.

K. Eichner (1962) classifies dentition defects on a somewhat different principle. He proceeds from the position put forward by G. Steinhardt (1951),

where the existence of four protective zones with a normal bite is affirmed, holding its height. These zones are formed by premolars and molars. In the presence of all teeth, dental arches have four protective zones - two on each side of the jaw. Depending on the number of preserved zones, all dentitions are divided into three groups. The first (A) includes dentitions having antagonists in all four protective zones; in the second (B) - dentitions that have partially lost their protective zones; in the third (B) - dentition without antagonists.

It should be noted that any classification makes it easier to study the clinic of partial loss of teeth, documentation contributes to mutual understanding between doctors and at the same time does not allow you to accurately determine the plan for prosthetics, since the choice of prosthesis design depends not only on the location of the defect, but also on the condition of the crowns, and also the supporting apparatus of the remaining teeth, on their position in relation to the occlusal plane, type of bite, structural features of the edentulous alveolar process, on the age of the patient, etc.

DISTURBANCES ARISING IN THE DENTAL SYSTEM WITH PARTIAL SECONDARY Adentia

After the loss of teeth in the dentition, the nature of the interdependence of form and function changes. Clinical picture it depends on:

– from the time elapsed since the loss of teeth;

– the number of lost teeth;

– location of teeth in the dentition;

– the role played by the teeth in chewing;

– type of ratio of dentition;

– condition of periodontium and hard tissues of preserved teeth;

– on the age and general condition of the patient's body.

The leading symptoms in the clinic of partial loss of teeth are:

1) violations of the continuity of the dentition;

2) functional dissociation - the decay of the dentition into independently acting groups teeth and the appearance in connection with this of three links:

– functioning center;

– traumatic node;

– non-functioning link, or atrophic block;

3) functional overload of periodontal remaining teeth;

4) secondary deformations of the occlusal surface of the dentition;

5) violations:

– functions of chewing and speech;

– functions of chewing and facial muscles;

- activity of the temporomandibular joints;

– aesthetic standards.

Depending on the type of changes that occur in the dentition after tooth loss, the following three degrees of severity of lesions are distinguished:

Compensated state- due to a defect in the dentition, which does not affect the shape and structure of the dentition and periodontium.

Subcompensated state- occurs as a result of intrasystemic restructuring in the dentition and periodontium: the crowns of the teeth lean towards the defect, three teeth appear between the teeth, the teeth opposite the defect are displaced in the vertical direction, and the periodontium is also rebuilt.

Decompensated state- takes place in cases where intrasystemic restructuring is supplemented by inflammatory phenomena in the periodontium, its destruction, when gingival and bone pockets appear.

Sub- and decompensated states occur with reactive insufficiency of the body, when the masticatory apparatus ceases to form the system and begins to destroy it, as a result of which a state of functional pathology sets in and, as a result, adaptive mechanisms are disrupted, which is clinically manifested by intrasystemic restructuring in the dentoalveolar system.

V. Yu. Milekevich (1964) in experiments with the use of radioactive Ca45 proved that the violation of Ca metabolism in the dissociated dentoalveolar system is generalized and does not depend on which jaw the teeth are removed, that this violation precedes clinical and radiological changes and increases over time. the development of destructive manifestations and that the restructuring of the bone tissue in this case occurs according to the type of osteoporosis (the atrophic process is accompanied by the replacement of tissue sections with cellular fibrous connective tissue). Moreover, with the onset of the period of sclerosis of bone tissues, the pathological process begins to progress and as a result, a “struggle” arises between the process of adapting tissues to new conditions that have arisen and function. The dentition, in which the integrity of the dentition is compromised, should be considered as a system with a risk factor. All this necessitates the use orthopedic treatment with the loss of even one tooth.

Resorption of the residual alveolar ridge in edentulous patients is a chronic, progressive, irreversible process that aggravates the general condition. The rate of resorption of the alveolar process depends on the type of structure

bone tissue. According to the results of x-ray examination, bone tissue can be:

- dense (characterized by a fine-meshed bone structure, thick trabeculae, a dense cortical plate; this type of tissue slowly atrophies);

- spongy (the structure of the bone tissue is large-celled, the cortical plate is less clearly distinguished);

– without cortex(bone trabeculae are thin, thin needle-like trabeculae are located along the edge of the alveolar process; tissue of this type quickly atrophies).

The most intensive resorption occurs in the first 6 months after tooth extraction; the degree of its severity in the region of the alveolar ridge is practically unlimited in volume and time.

Alveolar processes are very high (more than 1.5 cm), high (up to 1.5 cm), medium height (up to 1 cm), low (up to 0.5 cm), very low (less than 0.5 cm). The lower the height of the alveolar process, the more unfavorable conditions arise during the prosthesis performing the function of transferring vertical load and stabilizing it due to the insufficient size of the alveolar ridge, since in these cases the support areas and resistance to horizontal displacement are small.

The shape of the alveolar ridges are: semi-oval, trapezoidal, dome-shaped, wedge-shaped, ridge-shaped, flat. Surface nature

and the shape of the alveolar ridge should ensure an even distribution of masticatory pressure over the mucosa covering it and at the same time allow easy application and removal of the prosthesis.

TISSUE PROSTHETIC FIELD

When examining the mucous membrane of the edentulous areas of the alveolar process, information is obtained about its thickness, degree of compliance, pain sensitivity, necessary to determine the area of the prosthetic bed.

According to M. Spreng (cited by A. I. Evdokimov, 1974), in the upper jaw, the compliance of the mucous membrane when a ball is immersed in it under a pressure of 200 g varies from 0.6 to 1.5 mm. On the lower jaw, the amplitude of compliance is 0.2–0.6 mm. Accordingly, M. Spreng classifies the compliance of the mucous membrane as follows: up to 0.4 mm - small; up to 0.9 mm - medium; above 0.9 mm - large.

Lynd (quoted by E. I. Gavrilov, 1984), taking into account the degree of mucosal compliance on the hard palate, distinguishes the following four zones:

1. The area of the sagittal suture is a medial (median) fibrous zone that does not have a submucosal layer; her flexibility is negligible.

2. The alveolar process is a peripheral fibrous zone, almost without a submucosal layer.

3. The region of the transverse palatine folds is covered with a mucous membrane that has medium degree compliance.

4. The posterior third of the hard palate - has a submucosal layer rich in mucous glands and containing a little adipose tissue: it has most compliance.

As shown by the results of histological and topographic studies (vessel filling) carried out by V. S. Zolotko (1963, 1965), the degree of compliance of the mucous membrane covering various parts of the alveolar processes and part of the hard palate depends directly on the density of vascular fields, the density of which increases (toward line A). It is the vessels, due to the ability to quickly empty (due to the formation of anastomoses with the maxillary cavity, with the nasal cavity, with deep layers of bone tissue) and refill with blood, that can create conditions for reducing the volume of tissue. Areas of the mucous membrane of the hard palate with extensive vascular fields, which, as a result, have, as it were, spring, shock-absorbing properties, are called buffer zones.

C. Suplee (quoted by A. I. Evdokimov, 1974) focuses on the state of the mucous membrane of the prosthetic bed and, depending on this, divides it into four classes:

1. Slightly pliable, dense mucosa with natural folds quite distant from the top of the alveolar process (bridles of the lips, tongue, buccal bands). Such a mucous membrane covers well-defined alveolar processes and is a convenient support for the prosthesis. She visits healthy people normosthenic constitution.

2. Dense, thinned, atrophied mucosa, covering the alveolar processes and palate with a thin layer. Places of attachment natural folds are closer to the top of the alveolar process. Such a mucous membrane is less convenient for supporting a removable prosthesis. It happens in people of an asthenic constitution, more often of advanced or advanced age.

3. Loose mucous membrane covering the alveolar processes and the posterior third of the hard palate, often a low alveolar process. Such a mucous membrane occurs in diseases of periodontal tissues. Patients in these cases need preliminary treatment - dehydration therapy.

4. The mucous membrane, the movable strands of which are located longitudinally and are easily displaced with a slight pressure of the impression mass. Such is the mucosa of the atrophied alveolar process with a more protruding soft crest. Prosthetics in such cases is possible only after special training. This type mucous membranes occur in various general diseases from the side cordially- vascular system, with endocrine and other diseases.

The state of the alveolar processes, the palate and the mucous membrane covering them must be taken into account during prosthetics, since the basis of the prosthesis should be placed on tissues that are equally pliable when pressure is applied to them. The decision to replace FSPP with partial secondary adentia is based on the theory that the remaining teeth used for clasps retain alveolar bone. At the same time, occlusion

ionic forces and muscle activity on the working side increase, neuromuscular control over the movements of the lower jaw increases. This is due to the proprioceptive properties of the periodontal ligament of the remaining supporting teeth. In addition, FHPPs are well fixed and stabilized, and are also able to fix the initial height of the occlusion.

In the process of diagnosing the disease and planning treatment, as well as during further monitoring of the patient, it is necessary to take into account the following parameters of periodontal abutment teeth:

– the amount of bone tissue;

– tooth mobility;

– pocket depth;

– the width of the attached gingiva;

– the degree of inflammation of the surrounding tissues.

The prognosis of the functioning of FSPP depends on the condition of the periodontium of the abutment teeth.

Examination of patients.

Tasks of prosthetics of partial secondary adentia

The manufacture of PSPP should be preceded by a thorough examination of patients aimed at identifying the etiology, pathogenesis, clinic this disease. This allows you to correctly diagnose, outline a set of therapeutic measures to restore the integrity and functions of the dental system.

At the appointment with the dentist, the patient must come with an outpatient card, which indicates his passport data. The doctor, based on the results of the examination of the condition of the hard and soft tissues of the oral cavity, as well as the topography of the defect in the dentition, may recommend the patient prosthetics

		Table 1
Determination of indications for the use of orthopedic structures
	with partial secondary adentia
	Survey
		Criteria for evaluating results
1. Subjective:	Interview	Complaints disturbing the patient in connection with the disease
a) complaints;		vanity. The degree of effectiveness previously held
b) history		foot therapeutic, orthopedic treatment;
		previous diseases (Botkin's disease,
		TBC, etc.), allergic status
2. Objective:	visual	The manifestation of signs of the disease on the face,
a) physical examination;	the study	caused by the absence of teeth, the nature and
		mouth opening stump, TMJ condition.
		Changes in the oral mucosa.
		Topography of the defect.
		Changes in the dentition.
		Height clinical crowns abutment teeth.

In orthopedic dentistry, partial absence of teeth implies a lack of one or more units. In terms of the impact on functionality and aesthetics, the diagnosis of “partial absence of teeth (partial adentia)” is very ambiguous, because if 2–3 teeth are missing, this is one situation, and if 1–15 is completely different. That is why some experts began to distinguish such a variety as multiple adentia, when more than 10 teeth are missing. However, even without this division, partial adentia has forms and classes that are important to mention.

Forms of partial edentulous teeth

Primary adentia. Absence or death of rudiments of teeth at the stage prenatal development. This form partial adentia is quite rare and is caused by hereditary factors or diseases and infections that have arisen during pregnancy (hypothyroidism, ichthyosis, pituitary dwarfism). Primary adentia is often combined with an irregular shape of the teeth or underdevelopment of the alveolar processes;

A person was born with a full set of teeth, but lost some of them due to injuries or dental diseases and complications. Partial secondary absence of teeth is a very common disease. According to statistics, more than 75% of people lose one or more teeth during their lifetime.

Classification of partial adentia

The most popular classification of partial adentia was developed by the American dentist Edward Kennedy. Despite the fact that this happened back in the twenties of the last century, they are actively working on it today. In total, Kennedy identified four main classes of partial adentia, with a focus on which a rehabilitation plan is drawn up.

Kennedy classification of partial absence of teeth

First grade. Partial edentulous with bilateral end defect: absence of molars on both sides of the jaw.
Second class. Unilateral end defect when the patient has lost chewing teeth on one side of the jaw.
Third class. Unilateral included defect. Missing some molars or front teeth.
Fourth grade. Included anterior teeth defect. Completely missing teeth in the smile zone.

Treatment of partial adentia

If the patient has a complete or partial absence of teeth, treatment is carried out using two methods: implantation and classical prosthetics. The first method is a priority, since only an implant is able to fully replace the tooth root and prevent bone tissue atrophy. On the other hand, it is not always possible to carry out implantation due to a number of contraindications, as well as due to a banal lack of funds. In this case classical prosthetics- the only way out.

Treatment methods for partial adentia

Fixed bridge prosthesis

The most popular option when restoring one or more missing teeth in a row. A similar prosthesis is attached to the supporting healthy teeth or telescopic crowns. Often when restoring one tooth in neighboring teeth a recess is made, after which the structure is connected by a special bridge, which is attached using composite materials (Maryland prosthesis). The bridge can be metal, metal-ceramic and ceramic (to restore the frontal group of teeth).

relative durability
lower cost compared to implantation
good performance indicators

turning neighboring teeth
possible allergy on metal components
mediocre aesthetics

Dental crown and bridge on implants

It is used for a single defect and in the same situations as the classic one. bridge prosthesis but supported by implants rather than adjacent teeth.

good aesthetics and functionality
preservation of bone volume at the implantation site
durability

high price

Removable and conditionally removable dentures on implants

They are used in the case of multiple adentia, when the doctor removes the remaining teeth and puts an implant-supported structure that completely imitates the jaw. The type of prosthesis (removable or conditionally removable) depends on the method of attachment. Button mount allows you to remove the prosthesis from the oral cavity independently. Beam fastening (implants are connected to each other by a special beam) implies that the prosthesis will be removed only in the dentist's office.

reliability
good functionality and acceptable aesthetics
durability (the old prosthesis is changed after 7 - 10 years, implants can stand for life)

high price
the need to remove the remaining teeth

Deformation of the bite with partial absence of teeth

The state of the dentoalveolar system with partial absence of teeth is a topic for a separate discussion. Even the loss of one tooth provokes the displacement of the entire dentition, as the body in this way tries to restore the correct distribution of the load. This process begins in the immediate vicinity of the lost tooth, however, over time, the deformation of the dentition in the partial absence of teeth becomes more pronounced, especially when a significant number of them are lost. The most accurate classification of changes in the position of teeth during adentia was proposed by Dr. E. I. Gavrilov.

Classification of partial absence of teeth according to Gavrilov

Vertical movement (elongation of the teeth). Often occurs with the loss of antagonist teeth.
Mesial and distal movement.
Oral and vestibular movement of teeth.
Combined movement of teeth (rotation with an inclination, fan-shaped divergence, and so on).

Correction of deformities of the teeth occurs with the help of orthodontic, orthopedic and surgical techniques: at serious complications placement of a prosthesis or implants may be delayed. Determination of bite in the partial absence of teeth includes the calculation of the occlusal height, prosthetic plane, height lower section face and central ratio of the jaws.

Adentia(adentia; a - prefix, meaning the absence of a sign, corresponds to the Russian prefix "without" + dens - tooth) - the absence of several or all teeth. There are acquired (as a result of a disease or injury), congenital hereditary adentia.

In the special literature, a number of other terms are used: defect of the dentition, absence of teeth, loss of teeth. Partial secondary adentia as an independent nosological form of damage to the dentoalveolar system is a disease of the dentition or both dentitions, characterized by a violation of the integrity of the dentition of the formed dentoalveolar system in the absence pathological changes in other parts of this system.

With the loss of part of the teeth, all organs and tissues of the dentition can adapt to a given anatomical situation due to the compensatory capabilities of each organ of the system. However, after the loss of teeth, significant changes can occur in the system, which are classified as complications. These complications are discussed in other sections of the textbook.

In the definition of this nosological form, next to the classical term "adentia" is the definition of "secondary". This means that the tooth (teeth) is lost after the final formation of the dentition as a result of a disease or injury, i.e., the concept of "secondary adentia" contains a differential diagnostic sign the fact that the tooth (teeth) formed normally, erupted and functioned for some period. It is necessary to single out this form of damage to the system, since a defect in the dentition can be observed with the death of the rudiments of the teeth and with a delay in eruption (retention).

Partial adentia, according to WHO, along with caries and periodontal diseases, is one of the most common diseases of the dentition. It affects up to 75% of the population in various regions of the globe.

Analysis of the study of dental orthopedic morbidity maxillofacial region according to the data of negotiability and planned preventive sanitation of the oral cavity, it shows that the secondary partial adentia ranges from 40 to 75%. The prevalence of the disease and the number of missing teeth correlate with age.

In terms of frequency of deletion, the first place is occupied by the first permanent molars. Rarely, the teeth of the anterior group are removed.

Etiology and pathogenesis

Among etiological factors that cause partial adentia, it is necessary to distinguish between congenital (primary) and acquired (secondary).

The causes of primary partial adentia are violations of the embryogenesis of dental tissues, as a result of which there are no rudiments of permanent teeth. This group of reasons should also include a violation of the eruption process, which leads to the formation of impacted teeth and, as a result, to primary partial adentia. Both of these factors can be inherited.

The most common causes of secondary partial adentia are caries and its complications - pulpitis and periodontitis, as well as periodontal disease - periodontitis. In some cases, tooth extraction is due to untimely appeal for treatment, resulting in the development of persistent inflammatory processes in the periapical tissues. In other cases, this is a consequence of incorrectly performed therapeutic treatment.

Sluggish, asymptomatic necrobiotic processes in the dental pulp with the development of granulomatous and cystogranulomatous processes in the periapical tissues, cyst formation in cases of a complex surgical approach for resection of the root apex, cystotomy or ectomy are indications for tooth extraction. Removal of teeth treated for caries and its complications is often caused by spalling or splitting of the crown and root of the tooth, weakened by a large mass of the filling due to a significant degree of destruction of the hard tissues of the crown.

The occurrence of secondary adentia is also caused by injuries of the teeth and jaws, chemical (acid) necrosis of the hard tissues of the crowns of the teeth, surgical interventions about chronic inflammatory processes, benign and malignant neoplasms in the jaw bones. In accordance with the fundamental points of the diagnostic process in these situations, partial secondary adentia recedes into the background in the clinical picture of the disease.

The pathogenetic foundations of partial secondary adentia as an independent form of damage to the dentoalveolar system are due to large adaptive and compensatory mechanisms dental system. The onset of the disease is associated with the extraction of a tooth and the formation of a defect in the dentition and, as a consequence of the latter, a change in the function of chewing.

Rice. 97. Changes in the functional links of the dentoalveolar system in adentia.
a - functional centers; 6 - non-functional links.

A single morphologically functional dentoalveolar system disintegrates in the presence of non-functioning teeth (these teeth are devoid of antagonists) and groups of teeth, the functional activity of which is increased (Fig. 97). Subjectively, a person who has lost one, two or even three teeth may not notice a violation of the function of chewing. However, despite the absence of subjective symptoms of damage to the dentition, significant changes occur in it.

Increasing over time, the quantitative loss of teeth leads to a change in the function of chewing. These changes depend on the topography of defects and the quantitative loss of teeth: in areas of the dentition where there are no antagonists, a person cannot chew or bite off food, these functions are performed by preserved groups of antagonists. The transfer of the biting function to a group of canines or premolars due to the loss of anterior teeth, and in case of loss of chewing teeth, the function of chewing to a group of premolars or even anterior group of teeth disrupts the functions of periodontal tissues, muscular system, elements of the temporomandibular joints.

So, in the case shown in Fig. 97, biting off food is possible in the region of the canine and premolars on the right and left, and chewing in the region of the premolars on the right and the second and third molars on the left.

If one of the groups of chewing teeth is missing, then the balancing side disappears; there is only a fixed functional center of chewing in the area of the antagonistic group, i.e., the loss of teeth leads to a violation of the biomechanics of the lower jaw and periodontium, a violation of the patterns of intermittent activity of the functional centers of chewing.

With intact dentition, after biting off food, chewing occurs rhythmically, with a clear alternation of the working side in the right and left groups of chewing teeth. The alternation of the load phase with the rest phase (balancing side) causes a rhythmic connection to the functional load of periodontal tissues, characteristic contractile muscle activity and rhythmic functional loads on the joint.

With the loss of one of the groups of chewing teeth, the act of chewing takes on the character of a reflex given in a certain group. From the moment of the loss of a part of the teeth, a change in the function of chewing will determine the state of the entire dentoalveolar system and its individual links.

I. F. Bogoyavlensky (1976) points out that changes that develop under the influence of function in tissues and organs, including bones, are nothing but “functional restructuring”. It can proceed within the limits of physiological reactions. Physiological functional restructuring is characterized by such reactions as adaptation, full compensation and compensation at the limit.

The works of I. S. Rubinov proved that the effectiveness of chewing with various options adentia practically makes 80 — 100%. Adaptive-compensatory restructuring of the dentition, according to the analysis of masticograms, is characterized by some changes in the second phase of chewing, the search for the correct location food bolus, the total lengthening of one complete chewing cycle. If normally, with intact dentition, it takes 13-14 s to chew the almond kernel (hazelnut) weighing 800 mg, then if the integrity of the dentition is violated, the time is extended to 30-40 s, depending on the number of lost teeth and remaining pairs of antagonists. Based on the fundamental provisions of the Pavlovsk school of physiology, I. S. Rubinov, B. N. Bynin, A. I. Betelman and other domestic dentists proved that in response to changes in the nature of chewing food with partial adentia, the secretory function salivary glands, stomach, slow down the evacuation of food and intestinal peristalsis. All this is nothing but a general biological adaptive reaction within the limits of the physiological functional restructuring of the entire digestive system.

Pathogenetic mechanisms of intrasystemic restructuring in secondary partial adentia according to the state of metabolic processes in the jaw bones were studied in an experiment on dogs. It turned out that in early dates after partial removal teeth (3-6 months), in the absence of clinical and radiological changes, changes occur in the metabolism of the bone tissue of the jaws. These changes are characterized by an increased intensity of calcium metabolism compared to the norm. At the same time, in the jaw bones in the region of teeth without antagonists, the degree of severity of these changes is higher than at the level of teeth with preserved antagonists. An increase in the incorporation of radioactive calcium into the jawbone in the area of functioning teeth occurs at the level of a practically unchanged content of total calcium (Fig. 98). In the area of teeth that are out of function, a significant decrease in the content of ash residue and total calcium is determined, reflecting the development of initial signs of osteoporosis. At the same time, the content of total proteins also changes. A significant fluctuation in their level in the jawbone is characteristic, both at the level of functioning and non-functioning teeth. These changes are characterized by a significant decrease in the content of total proteins in the 1st month of the creation of an experimental model of secondary partial adentia, then a sharp rise in it (2nd month) and again a decrease (3rd month).

Consequently, the response of the jaw bone tissue to the changed conditions of the functional load on the periodontium is manifested in a change in the intensity of mineralization and protein metabolism. This reflects the general biological regularity of the vital activity of bone tissue under the influence of adverse factors, when the disappearance of mineral salts, but devoid of mineral component the organic base is preserved for some time in the form of osteoid tissue.

Minerals bones are quite labile and certain conditions can be "extracted" and again "deposited" under favorable, compensated states or conditions. Protein base is responsible for the processes of metabolism in the bone tissue and is an indicator of ongoing changes, regulates the processes of deposition of mineral substances.

The established pattern of changes in the exchange of calcium and total proteins in the early periods of observation reflects the reaction of the jaw bone tissue to new conditions of functioning. Here, compensatory capabilities and adaptive reactions are manifested with the inclusion of all defense mechanisms bone tissue. In that initial period when eliminating functional dissociation in the dentition caused by secondary partial edentulous, develop reverse processes, reflecting the normalization of metabolism in the bone tissue of the jaws [Milikevich V. Yu., 1984].

The duration of the action of unfavorable factors on the periodontium and jaw bones, such as increased functional load and complete shutdown from function, leads the dentoalveolar system to a state of "compensation at the limit", sub-decompensation. The dentoalveolar system with impaired integrity of the dentition should be considered as a system with a risk factor.

Clinical picture

Patients' complaints are different character. They depend on the topography of the defect, the number of missing teeth, the age and gender of the patients.

The peculiarity of the studied nosological form is that it is never accompanied by a feeling of pain. At a young age and often at adulthood the absence of 1-2 teeth does not cause any complaints from patients. Pathology is detected mainly during dispensary examinations, with planned rehabilitation oral cavity.

In the absence of incisors, canines, complaints about aesthetic flaw, impaired speech, saliva splashing when talking, inability to bite off food. If there are no chewing teeth, patients complain of a violation of the act of chewing (this complaint becomes dominant only with a significant absence of teeth). More often, patients note inconvenience when chewing, the inability to chew food. Complaints about an aesthetic defect in the absence of premolars in the upper jaw are not uncommon. It is necessary to establish the reason for the extraction of teeth, since the latter is important for overall assessment state of the dentoalveolar system and prognosis. Be sure to find out whether orthopedic treatment was previously carried out and what designs of dentures. It is indisputable that it is necessary to ascertain the general state of health in this moment which can undoubtedly affect the tactics of medical manipulations.

On external examination, usually facial symptoms missing. The absence of incisors and canines in the upper jaw is manifested by the symptom of "retraction" upper lip. With a significant absence of teeth, "retraction" of the soft tissues of the cheeks and lips is noted. Partial absence of teeth in both jaws without the preservation of antagonists is often accompanied by the development of angular cheilitis (jamming); during swallowing movement, the lower jaw makes a large amplitude of vertical movement.

When examining the tissues and organs of the mouth, it is necessary to carefully study the type of defect, its length (size), the condition of the mucous membrane, the presence of antagonizing pairs of teeth and their condition (hard tissues and periodontal), as well as the condition of the teeth without antagonists, the position of the lower jaw in central occlusion and in a state of physiological rest. The examination must be supplemented with palpation, probing, determining the stability of the teeth, etc. It is mandatory x-ray examination periodontal teeth, which will be supporting for various designs dentures.

The variety of options for secondary partial adentia, which have a significant impact on the choice of a particular treatment method, has been systematized by numerous authors.

The classification of dentition defects developed by Kenedy has become the most widespread, although it does not cover combinations that are possible in the clinic.

The author identifies four main classes. Class I is characterized by a defect that is bilateral distally not limited by teeth, II is characterized by a defect that is unilateral distally not limited by teeth; III - unilateral defect limited distally by teeth; Class IV - the absence of front teeth. All types of defects in the dentition without distal limitation are also called terminal, with distal limitation - included. Each defect class has a number of subclasses. General principle subclassing - the appearance of an additional defect inside the preserved dentition. This significantly affects the course of the clinical justification of tactics and the choice of one or another method of orthopedic treatment (type of denture).

Diagnosis

Diagnosis of secondary partial adentia is not difficult. The defect itself, its class and subclass, as well as the nature of the patient's complaints, testify to the nosological form. It is assumed that all additional laboratory methods studies have not established any other changes in the organs and tissues of the dentoalveolar system.

Based on this, the diagnosis can be formulated as follows:

Secondary partial adentia on the upper jaw, IV class, the first subclass according to Kenedy. Aesthetic and phonetic defect;
. secondary partial adentia on the lower jaw, class I, second subclass according to Kenedy. Chewing dysfunction.

Clinics with offices functional diagnostics, it is advisable to establish the percentage loss of chewing efficiency according to Rubinov.

During the diagnostic process, it is necessary to differentiate primary from secondary adentia.

Primary adentia due to the absence of tooth rudiments is characterized by underdevelopment in this area of the alveolar process, its flattening. Often, primary adentia is combined with diastemas and tremas, an anomaly in the shape of the teeth. Primary adentia with retention is usually diagnosed after x-ray examination. It is possible to make a diagnosis after palpation, but with subsequent radiography.

Secondary partial adentia as an uncomplicated form must be differentiated from concomitant diseases, such as periodontal disease (without visible pathological tooth mobility and the absence of subjective discomfort), complicated by secondary adentia.

If secondary partial adentia is combined with pathological wear of the hard tissues of the crowns of the remaining teeth, it is fundamentally important to establish whether there is a decrease in the height of the lower face in the central occlusion. This significantly affects the treatment plan.

Diseases with pain syndrome in combination with secondary partial adentia, as a rule, they become leading and understand the relevant chapters.

The rationale for the diagnosis of "secondary partial adentia" is the compensated state of the dentition after partial loss of teeth, which is determined by the absence of inflammation and dystrophic processes in the periodontium of each tooth, the absence pathological abrasion hard tissues, deformities of the dentition (Popov-God it phenomenon, displacement of teeth due to periodontitis). If the symptoms of these pathological processes are established, then the diagnosis changes. So, in the presence of deformations of the dentition, a diagnosis is made: partial secondary adentia, complicated by the Popov-Godon phenomenon; Naturally, the treatment plan and medical tactics of managing patients are already different.

Treatment

Treatment of secondary partial adentia is carried out with bridge-like, removable plate and clasp dentures.

A bridge-like and fixed prosthesis is a medical device that serves to replace the partial absence of teeth and restore chewing function. It is strengthened on natural teeth and transmits chewing pressure to the periodontium, which is regulated by the periodontal muscle reflex.

It is generally accepted that treatment with non-removable bridges can restore up to 85-100% chewing efficiency. With the help of these prostheses, it is possible to fully eliminate phonetic, aesthetic and morphological disorders of the dentoalveolar system. Almost complete compliance of the design of the prosthesis with the natural dentition creates the prerequisites for rapid adaptation patients to them (from 2-3 to 7-10 days).

A removable lamellar prosthesis is a medical device that serves to replace the partial absence of teeth and restore chewing function. It is attached to natural teeth and transmits chewing pressure to the mucous membrane and bone tissue of the jaws, regulated by the gingivomuscular reflex (Fig. 101).

Taking into account the fact that the base of the removable laminar prosthesis completely relies on the mucous membrane, which, according to its histological structure, is not adapted to the perception of chewing pressure, chewing efficiency is restored by 60-80%. These prostheses allow to eliminate aesthetic and phonetic disorders in the dentoalveolar system.

However, the methods of fixation and a significant area of the basis complicate the mechanism of adaptation, lengthen its period (up to 1–2 months).

A clasp prosthesis is a removable medical apparatus for replacing the partial absence of teeth and restoring chewing function.

It is strengthened behind natural teeth and relies both on natural teeth and on the mucous membrane, masticatory pressure is regulated in combination through periodontal and gingivomuscular reflexes.

The possibility of distribution and redistribution of masticatory pressure between the periodontium of the abutment teeth and the mucous membrane of the prosthetic bed, combined with the possibility of refusing to prepare teeth, high hygiene and functional efficiency, made these dentures one of the most common modern species orthopedic treatment. Almost any defect in the dentition can be replaced with a clasp prosthesis, with the only caveat that with certain types defects change the shape of the arc.

In the process of biting off and chewing food, chewing pressure forces of various duration, magnitude and direction act on the teeth. Under the influence of these forces, responses occur in periodontal tissues and jaw bones.

Knowledge of these reactions, influence on them various kinds Dental prostheses is the basis for the choice and reasonable use of one or another orthopedic apparatus (denture) for the treatment of a particular patient.

Based on this basic provision, the following clinical data significantly influence the choice of the design of the denture and abutment teeth in the treatment of partial secondary adentia: the class of the dentition defect; defect length; condition (tonus) of chewing muscles.

The final choice of treatment method can be influenced by the type of occlusion and some features associated with the profession of patients.

Lesions of the dentoalveolar system are very diverse, and there are no two patients with exactly the same defects. The main differences in the state dental systems two patients are the shape and size of the teeth, the type of bite, the topography of defects in the dentition, the nature of the functional relationships of the dentition in functionally oriented groups of teeth, the degree of compliance and the threshold of pain sensitivity of the mucous membrane of the edentulous areas of the alveolar processes and the hard palate, the shape and size of the edentulous areas of the alveolar processes .

General state organism must be taken into account when choosing the species medical device. Each patient has individual characteristics, and in this regard, two outwardly identical in size and location of the defect of the dentition require a different clinical approach.

Theoretical and clinical basis choice of method of treatment with fixed bridges

The term "bridge" came to orthopedic dentistry from technology during the period of rapid development of mechanics, physics and reflects the engineering structure - the bridge. It is known in the art that the design of a bridge is determined based on the expected theoretical load, i.e. its purpose, span length, ground conditions for supports, etc.

Almost the same problems are faced by an orthopedic doctor with a significant correction for the biological object of influence of the bridge structure. Any design of a dental bridge includes two or more supports (medial and distal) and an intermediate part (body) in the form artificial teeth(Fig. 102).

Rice. 102. Varieties of fixed prostheses used for the treatment of secondary adentia.

Fundamentally various conditions The statics of a bridge as an engineered structure and a fixed dental bridge are as follows:

Bridge supports have a rigid, fixed base, while fixed bridge supports are mobile due to the elasticity of periodontal fibers, the vascular system, and the presence of a periodontal gap;
. the supports and span of the bridge experience only vertical axial loads in relation to the supports, while the periodontium of the teeth in the bridge-like non-removable denture experiences both vertical axial (axial) loads and loads at different angles to the axes of the supports due to the complex relief of the occlusal surface of the supports and the body of the bridge and the nature of the chewing movements of the lower jaw;

Rice. 103. Statics of the bridge as an engineering structure.

In the abutments of the bridge and the bridge prosthesis and the span after the removal of the load, the resulting internal stresses compression and tension subside (extinguish); the structure itself comes to a “calm” state;
. the supports of a fixed bridge prosthesis return to their original position after the load is removed, and since the load develops not only during chewing movements, but also when swallowing saliva and establishing dentition in central occlusion, these loads should be considered as cyclic, intermittent-constant, causing a complex set of responses from the periodontium (see "Biomechanics of the periodontium").

Thus, the statics of a bridge with two-sided, symmetrically located supports is considered as a beam lying freely on rigid "bases". With a force K applied to the beam in the center, the latter bends by some amount S. At the same time, the supports remain stable (Fig. 103).

A fixed dental bridge with bilateral, symmetrically located supports should be considered as a beam rigidly fixed on an elastic base (Fig. 104).

The load K, applied in the center of the intermediate part (body) of the bridge, is evenly distributed between the supports.

K=P1+P2; R1R2

The force K, when applied to the body of a bridge, causes a moment of rotation (M), which is equal to the product of the magnitude of the force K and the length of the arm (a or b). Since when the force K is applied in the center of the body of the bridge, the arms a and brava, then two moments of rotation - Ka and K "b, having opposite signs, balanced.

If the force K moves towards one of the supports (Fig. 105), then the moment of rotation and the load in the area of \u200b\u200bthis support increase, and at the opposite one they decrease (shoulder a<б).

The load on the supporting tooth is always proportional to the distance of the support from the place of application of the force.

Provided that the masticatory pressure realized in the force K coincides with the functional (physiological) axis of one of the supporting teeth, then this tooth bears the full load, and in the second support the force K will be of the opposite sign.

The supports move under load - they sink deep into the dental alveolus (toward the bottom of the alveolus) until equal but oppositely directed forces from the periodontal fibers arise. A biostatic balance of forces is established - the applied force and the elastic deformation of the periodontal fibers and bone tissue. This relationship can be determined statically by two counteracting moments of the “bridge-periodontium” system directed against each other. After the load is removed, the supports return to their original position. As a result, they make a path equal to the values of nPBx

Under the action of a vertical load and a load at an angle during lateral movements of the lower jaw, deflection S and torque occur in the body of the bridge. As a result, the supports experience a tilting moment by the value< а. На внутренней стороне опор волокна периодонта сжимаются (+), на наружной — растягиваются (—), находясь в уравновешенном состоянии (см. рис. 105). Степень отклонения опор от исходного состояния (величина а) зависит от параметров тела мостовидного протеза, выраженности бугорков на окклюзионной поверхности, величины перекрытия тела мостовидного протеза в области передних зубов.

The main provisions of statics given in relation to the dental bridge dictate the need to systematize the types of bridges depending on the location of the supports, their number and the shape of the intermediate part.

Rice. 106. Types of bridge-like non-removable dentures, depending on the location and number of supports. Explanation in the text.

So, depending on the location of the supports and their number, it is necessary to distinguish 5 types of bridges: 1) a bridge with a bilateral support (Fig. 106, a); 2) with an intermediate additional support (Fig. 106, b); 3) with double (medial or distal) support (Fig. 106, c); 4) with paired double-sided supports (Fig. 106, d); 5) with a one-sided console (Fig. 106, e).

The shape of the dental arch is different in the anterior and lateral areas, which naturally affects the intermediate part of the bridge. So, when replacing the front teeth, the intermediate part is arched, when replacing the chewing teeth, it approaches a rectilinear shape (Fig. 107, a, b). With a combination of defects in the dentition in the anterior and lateral sections and replacing them with one bridge prosthesis, the intermediate part has a combined shape (Fig. 107, c, d).

The presence of a cantilever element in the design of a bridge prosthesis, an arched or rectilinear body of a bridge prosthesis, a different direction of the axes of the supporting teeth due to their anatomical location in the dentition significantly affect biostatics and should be taken into account when justifying treatment with bridge prostheses.

Rice. 107. Types of bridge-like non-removable dentures depending on the shape of the intermediate part (body). Explanation in the text.

Rice. 108. Statics of the biomechanical system "bridge fixed denture - periodontium" with a cantilever element (indicated by an arrow). Explanation in the text.

In particular, when turning on the cantilever element, it is necessary to take into account the length of the lever that counteracts the lever of the applied force (see Fig. 106).

It is generally accepted that the longer the arm e (M1 \u003d P1. e) compared with the shoulder c (M2 \u003d K "c), the more it counteracts the eccentric load K on the console. In the state of equilibrium, the moment of rotation of the lever e acts against the moment of the lever c , i.e. Mi>M2 (Fig. 108) When the opposite lever is shortened, the fulcrum near the console is loaded under pressure, becomes a point of rotation, and the remote fulcrum experiences "stretching", "dislocation" - a moment of rotation with a negative sign.

With an arcuate body of a bridge prosthesis, the applied force K always acts in an eccentric vertical direction relative to the axes of the supports (canines, premolars). The larger the radius of the arc, the greater the negative effect of the moment of rotation on the supports (Fig. 109, a).

The moment of rotation is expressed as M = K-a, where a is a segment of the perpendicular to the transversal line connecting the supports to each other. Under the action of force K, it becomes the axis of rotation, the moment of "overturning" of the supports. To neutralize this negative component, Schroeder points out the need to include chewing teeth in the support of a bridge with an arcuate body with the formation of the same length of counteraction levers (Fig. 109, b), bilateral power blocks of teeth. The moment of rotation must be compensated by them.

Rice. 109. Statics of the biomechanical system "bridge fixed prosthesis - periodontium" with an arched shape of the body of the prosthesis. a - double-sided single support; b — bilateral multiple support.

With a rectilinear shape of the body of the bridge prosthesis in the region of the lateral teeth, the vertical (centric or eccentric) chewing pressure is perceived by the complex relief of the chewing surface, where the slopes of the tubercles are inclined planes (Fig. PO). The force K, according to the wedge law, is decomposed into two components, of which the forces K (perpendicular to the axis) and the resulting forces Kr cause a moment of rotation. The latter, which is not compensated by anything, leads to vestibular-oral deviations of the supporting teeth (Fig. 111).

In a state of biostatic equilibrium, the moments of rotation are equal to each other М1 = М2; their value does not exceed the value of elastic deformation of periodontal fibers. To maintain this balance, it is necessary to create the same type of slopes of the vestibular and lingual (palatine) tubercles when modeling the chewing surface. As a compensation for the negative effect of the moment of rotation, one can consider the connection of additional supports lying in a different plane, in particular, canines or third molars.

The possibility of treatment with bridges, the application of additional masticatory load is based on the general biological position about the presence of physiological reserves in human tissues and organs. This allowed V. Yu. Kurlyandsky to put forward the concept of "reserve forces of the periodontium." It finds confirmation in the analysis of an objective study of periodontal pressure endurance - gnathodynamometry. The endurance limit of the periodontium to pressure is the threshold load, the increase of which leads to pain, for example, for premolars - 25-30 kg, molars - 40-60 kg. However, under natural conditions, when biting and chewing food, a person does not develop efforts until pain occurs.

Consequently, part of the periodontal endurance to the load is constantly realized in natural conditions, and part is a physiological reserve, realized under extreme conditions, in particular during illness.

It is accepted theoretically, approximately, to consider that out of 100% of the functional capabilities of an organ, 50% is normally spent, and 50% is a reserve. This is the main theoretical basis in the clinic for the selection and justification of the number of supporting teeth for a dental bridge and its structural elements, as well as systems for fixing removable dentures.

The load on the periodontium of the supporting teeth, its magnitude and direction are directly dependent on the state of the periodontal teeth-antagonists. Under natural conditions, the size of the food bolus between the teeth does not exceed the length of three teeth. Therefore, we can assume that the maximum load, for example, in the area of chewing teeth is possible from the total endurance of the second premolar and two molars (7.75-50% of which is 3.9); in the area of the anterior teeth - two central and two lateral incisors (4.5-2.25-50%).

Since the increase in chewing pressure will primarily determine the reaction of single-standing antagonist teeth, the contractile force of the chewing muscles will be regulated precisely through the periodontal muscle reflex of the latter. If the antagonist is a bridge, then the amount of impact from it is the total amount of periodontal endurance of all supporting teeth. Let us consider specific clinical situations when deciding on a reasonable choice of a method of treatment with bridges.

The patient does not have