In the manufacture of prostheses for a patient with complete loss of teeth, in addition to anatomical, functional impressions are required.
A functional impression is an impression obtained using an individual tray, the edges of which are decorated with functional samples.
Individual spoons can be made from various materials. They are made at the dental chair or in the laboratory.
Most spoons are now made in the laboratory.
For this purpose, according to the anatomical impression obtained) with a standard spoon, a plaster model is made and the boundaries of the spoon are drawn within the transitional fold (at the deepest point on the model).
AKR-P plastic blanks are softened in hot water or over a burner flame, placed on the model and tightly crimped within the boundaries. The excess is trimmed with scissors. If the edges do not fit tightly, they are reheated and pressed against the model. A handle is formed from scraps for the lower spoon by gluing it to the spoon with a very hot spatula.
The clinic showed that trays made from AKP-P plates are deformed during impression taking and have thin edges.
The spoon can be made from any quick hardening plastic. The plastic dough prepared for these purposes is rolled out to a thickness of about 2 mm, a shape is cut out of the plate, similar to blanks from AKP-P, and compressed according to the model coated with the Isokola layer. To harden the plastic, a model with a spoon is placed under an electric lamp or placed in warm water. So that the edges of the spoon do not deform when the plastic hardens, it is better to harden it in a pneumopolymerizer.
Much faster, you can make a fairly accurate individual spoon by pressing the speed
curing plastic or blanks from it in the apparatus of E. Ya. Vares or Yu. K. Kurochkin.
A uniform thickness, accurate and durable spoon is obtained if it is prepared through a wax composition. For this purpose, the wax plate, compressed according to the model within the boundaries and trimmed, is glued along the perimeter to the model and plastered into the cuvette in the reverse way. After melting the wax and insulating the gypsum mold, a base or quick-hardening plastic is laid and pressed. The cuvette is transferred to a clamp (frame) and polymerized. Cooled, processed and transferred to the doctor's office.
If there are canopies on the alveolar process or alveolar tubercles, an individual spoon is prepared according to the second layer of wax. The first layer of base wax, compressed according to the model and trimmed within the drawn boundaries, is covered with a thin layer of Vaseline. Apply a second layer of wax, crimp, trim. On the lower spoon, in the front section, a vertical handle measuring 10x10 mm is created.
The workpiece from the second layer of wax is removed from the model and plastered, placing it in the first half of the cuvette, without the model, with the handle down.
After replacing the wax with plastic and processing, the spoon is handed over to the doctor along with the model and the first wax layer.

Message Dr_Arut » Mon May 16, 2016 5:23 am

To obtain a functional impression in dentistry, an individual spoon is used, which is made according to an anatomical cast. An individual tray matches the prosthetic bed as closely as possible and allows for functional tests, so the impression more accurately reflects it. There are four main ways to make custom spoons, listed below in chronological order.

Making an individual spoon from quick-hardening plastic;
Production of an individual spoon from a plate of thermoplastic plastic by vacuum forming;
Production of an individual spoon from a plate of a photopolymer composite;
3D printing.

The oldest and most common method is the manufacture of a spoon from cold polymerization plastic (Protacryl-M, etc.). To do this, a plaster model is cast from ordinary plaster (class II) according to the anatomical cast. Cut the model on the trimmer. Draw the border of the future individual spoon with a chemical pencil. Usually the border passes 1-2 mm before reaching the vestibule of the oral cavity, i.e. 1-2 mm shorter than the edge of the removable denture base. Also, the edge of the spoon does not reach the frenulum and strands by 1-2 mm. This space is necessary for the correct shaping of the margins with thermoplastic or viscous silicone impression materials.

Making an individual spoon from quick-hardening plastic.
After the borders are drawn, the undercuts are isolated with wax so that the finished individual tray can be removed from the model. Warm up the base wax plate and press it evenly onto the model. Cut it along the previously drawn border. In the area of the palate and alveolar processes in the lateral section, round or square holes (windows) are made in wax to create stops on an individual spoon, which in these areas will be in contact with the oral mucosa. This is done to create a uniform gap between the spoon and the mucosa, which will be filled with a corrective silicone mass. The window area is lubricated with insulating varnish (Isokol-69, Pikasep, petroleum jelly, vegetable oil, etc.).

Next, cold polymerization plastic is kneaded according to the manufacturer's instructions (usually in a 2: 1 weight ratio of powder and monomer). The easiest way to model a spoon made of cold-cured plastic is to use a special silicone mold with a plinth-shaped model a few millimeters high. A thin polyethylene film (food film, etc.) is laid on the bottom of the mold, the mixed plastic is poured into the mold, leveled in the mold and covered with a second layer of film on top. It is left for a few minutes for the maturation of the plastic and the transition to the “dough stage”. After that, the upper (second) layer of the film is removed, the plastic is pressed against the model with its upper side, respectively, it turns over and the lower layer of the film is on top. Further, the plastic adapts to the model through the film. The film is also removed from the excess, i.e. plastic that has gone beyond the boundaries of the spoon, a handle is modeled. If it is necessary to model the finger supports on the spoon in the lateral sections, then this is also done from the surplus.

Next, the dental technician waits for the resin to harden. After hardening removes the spoon from the plaster model, if necessary, separates the wax from the spoon. Shortens the spoon according to the drawn borders on the model. If necessary, perforations are made on the tray for better adhesion to the impression mass.

A. Film on the form;
B. Filling the mold with plastic and applying a second film on top;
IN. Spoon modeling;
G. View of the finished spoon.
Advantages:

Cheapness;
No grips in the area of undercuts;
No need for special equipment.

Flaws:

Toxicity, as the technician inhales the monomer vapours;
Limited simulation time;
The inconvenience of grinding the spoon (the material can melt and clog the cutter);
The need to isolate undercuts on the model;
The inconvenience of modeling the handle.

Without which it is impossible to manufacture dentures in the modern world? Yes, without high-quality impressions (functional and anatomical, which we will analyze further). To make a suitable design, an imprint of the tissues of the upcoming prosthetic bed is needed. Mastering the techniques for obtaining high-quality impressions is a necessary stage in the career of every orthodontist. We will analyze the main classifications of these casts, the methods for obtaining them, as well as the materials used to make them.

What is this?

What are anatomical and functional impressions in dental orthopedics (orthodontics)? This is the name of the reverse (or negative) reflection of the patient's teeth, various soft and hard materials of the oral cavity - the palate, the alveolar process, the transitional folds of the mucous membranes, etc. The impression is obtained using special materials.

The history of anatomical and functional impressions in dentistry began in 1756! Then the German doctor Pfaff was the first to make such a print, using simple wax as an impression material.

Why are prints needed?

Why is an impression needed in orthodontics? It is on this basis that a positive model is made, which is an exact copy of the hard and soft tissues of the oral cavity.

Various impressions are used for diagnostic, therapeutic, educational, control and working purposes. Some models are valuable because they help clarify or refute the patient's diagnosis. Some are needed to make a prosthesis. And some allow you to evaluate the effectiveness of the orthopedic therapy (cast before and after it).

The so-called working functional impressions are needed for the further production of prostheses by specialists. Auxiliary help to study the "relationship" of the antagonist dentition.

Classification according to Gavrilov

The fundamental gradation in orthodontics is the division into functional and anatomical impressions. What is the difference? The first are created taking into account the functional compliance, the mobility of the matter that covers the prosthetic bed. The second, respectively, without such consideration.

Consider the classification of impressions:

Functional. Most often they are removed from the edentulous jaw. Less often - with the one where some teeth were preserved. The most important purpose is the basis for the manufacture of prostheses for edentulous patients. It is these prints that help determine the optimal ratio of the tissues of the oral cavity and the edges of the prosthesis adjacent to them. This is important for better fixation of the device, as well as for the correct distribution of the so-called masticatory pressure between the fundamental sections of the prosthetic bed. It is important to note that functional impressions are obtained by functional tests. The latter help to correctly shape the edges of the prints in relation to the position of movable tissues, which will later be located on the border with the prosthesis.
Anatomical. Additionally, they are divided into main and auxiliary. The first type is removed from the jaw, on which the prosthesis will be installed in the future. The second - from the antagonist jaw (upper or lower), on which there will be no prosthesis. The anatomical type is widely used in orthodontics to display the position of tissues (soft and hard) in the oral cavity. It is useful for making inlays, crowns, bridges and partially removable dentures.

An important difference between these varieties stands out from the characteristic. Obtaining functional impressions is important for making a complete denture for an edentulous jaw. Anatomical is more likely to be useful for partial dentures, bridge devices and other smaller-scale structures.

Another important difference between anatomical and functional imprints. For the first, standard impression trays are used. And for the second, these instruments are made individually for each patient. To better understand how impressions are taken, functional and anatomical, let's look at what is considered an impression tray.

Impression tray - what is it?

Impression trays are made at the factory from plastic or Their shape and volume are determined by many factors at once:

Patient's jaw.
Type, width of the dentition.
Location of the defect.
The height of the crowns of the remaining teeth.
Jaw expressiveness.

Even standard impression trays vary in shape and size. First of all, they are divided into those intended for the upper and for the lower jaw. The removal of functional impressions, as we said, is carried out with individual spoons.

Each of these instruments has a body and handles. The body of the spoon will consist of an alveolar concavity, an outer rim, and curves for the palate. For example, standard impression trays have ten sizes for the upper jaw, nine for the lower.

The use of varieties of spoons

When working with elastic materials for the impression, special spoons with holes are used. This is due to the fact that the base does not adhere well to the metal from which the standard spoon is made. Some specialists get out of this situation using their own resourcefulness: they stick a band-aid on the inside of an ordinary metal tool. The elastic base adheres better to its rough fabric surface.

Also, cutting the handles of such spoons with special metal scissors in case of their excessive length is considered medical ingenuity and amateur performance. If the handle, on the contrary, is short, then it is lengthened with a wax plate. But in the collection of a qualified specialist, there are usually standard spoons for any occasion, which saves him from such extreme measures.

The so-called partial spoons are used much less frequently. They are used in relation to jaws with scattered single teeth. The impression is necessary for the manufacture of crowns. Partial spoons are also used for teeth that do not have antagonists in front of them.

individual spoons

Functional impression with an individual spoon is carried out for edentulous jaws. Such instruments differ in the height of the sides, the expressiveness of the niche for a slightly smaller size. It is explained by the fact that the imprint should provide the specialist with more accurate data about the prosthetic bed.

Why do we need individual spoons? As a rule, it is difficult to find two edentulous jaws that are absolutely similar in external characteristics. For accurate fixation of the prosthesis, functional suction is necessary here, which is created by creating a negative pressure. To do this, it is necessary to perfectly match the surface of the prosthesis being made with the tissues of the prosthetic bed that will be in contact with it. Without a precise fit of the edges of the spoon to the borders of the valvular region, this result is difficult to achieve.

How is a custom spoon made? To begin with, using a standard tool in the orthodontic clinic, a full anatomical cast of the jaw is made. Then, in the laboratory, an individual plastic model is made on its basis.

Classification of the impression base according to Oxman

We figured out the impression spoons. The second important component is the materials for the functional impression. According to this classification, they can be divided into the following types:

crystallizing masses. This type includes "Dentol" (domestic zinc oxide paste), gypsum, eugenol.
thermoplastic masses. These are wax, stens, stomatopast, adhesive, Kerr and Weinstein masses.
elastic masses. This category includes stomalgin and algelast.
polymerizing masses. Silicone impression bases, ACT-100, styracryl.

Classification of the impression base according to Doinikov and Sinitsyn

Let's imagine another classification common in orthodontics, which separates the materials used to take functional and anatomical casts of the jaws.

At the beginning, two groups are distinguished. The first - according to the physical state of the material:

Elastic.
Polymerizing.
Thermoplastic.
Solid-crystalline.

The second gradation divides materials into categories according to their chemical nature:

Crystallizing materials

Let us characterize in more detail the substances that are most often used in orthodontics for taking anatomical and functional impressions. Here it is important to highlight its other name - semi-aqueous sulfate salt. It is obtained from ordinary natural gypsum, subjected to special heat treatment. As a result of this process, the material is converted from two-water to semi-aqueous.

The most suitable for dentistry is the alpha modification of medical plaster. It is obtained at elevated pressure and temperature in an autoclave. The substance is distinguished by the best strength and density.

Elastic materials

The basic raw material here is seaweed, from which alginic acid is obtained by technical means. The basis of the material is the sodium salt of this acid, which swells in water, forming a gel mass. To increase its elasticity and strength, gypsum, barium sulfate, white soot, etc. are additionally added to the impression composition. The gypsum turns the soluble gel into an insoluble one. The remaining components allow the gelation process to proceed more smoothly.

Requirements for functional impressions

The requirements for the resulting model are rooted in the requirements for the materials used to make the cast:

Making high-quality impressions is a necessary condition for obtaining a perfectly fitting denture. Therefore, considerable attention has been paid to this area in orthodontics. Today, there are special technologies for taking impressions, a wide range of materials and tools necessary for this work.

Functional impression: types, classification, requirements, individual casts, features of application and operation. Methods for making individual spoons in dentistry What is an individual spoon for prosthetics made of

Under any clinical conditions, only a functional impression with an individual spoon should be taken from the edentulous jaw.

Individual spoons can be made from:

1) metal (steel, aluminum) by stamping;

2) plastics:

a) basic (Ftorax, Ethacryl, Jarocryl) polymerization method;

b) fast-hardening (redonta, protacryl) by free molding;

c) standard plastic plates AKR-P;

d) light-curing plastic;

3) solar-cured materials with polymerization in special chambers or using a solar lamp;

4) thermoplastic impression masses (Stens);

Individual spoons are made in the laboratory or directly with the patient.

Making an individual plastic spoon in the laboratory.

In this case, an anatomical cast is taken with a standard spoon and a plaster model is cast on it. On the model, the dental technician draws the boundaries of the future individual spoon.

On the upper jaw, the border of the spoon runs from the vestibular side along the transitional fold, not reaching the deepest point of its arch by 1-2 mm. On the distal side, it covers the maxillary tubercles and runs along the line "A" behind the palatine fossae by 1-2 mm.

On the lower jaw, the border of the spoon runs from the vestibular side along the transitional fold, not reaching the deepest point of its arch by 1-2 mm, while bypassing the bands and frenulum of the lip. In the retromolar region, it is located behind the mucous tubercle, overlapping it by 1-2 mm.

On the lingual side, the border of the spoon overlaps the area corresponding to the retroalveolar region (muscleless triangle), not reaching the deepest place of the sublingual space by 1-2 mm and bending around the frenulum of the tongue.

From the foregoing, it can be seen that both on the upper and on the lower jaw, the border of the individual tray is 2-3 mm less than the borders of the prosthesis. This is done in order to leave room for the impression material. The displaced impression material forms the edges of the impression. And, conversely, the distal borders of the tray should be larger than the borders of the prosthesis so that the anatomical formations that are the guidelines for the distal edge of the prosthesis are well imprinted when the impression is taken.

After applying the borders, the dental technician covers the model with Izokol insulating varnish and proceeds to the manufacture of an individual tray from quick-hardening or basic plastic.

For the manufacture of an individual spoon from quick-hardening plastic, the required amount of material is kneaded to the doughy stage and a plate is made from it in the shape of the upper or lower jaw, which is crimped on the model along the outlined boundaries. Then, from small pieces of plastic "dough", a handle is made perpendicular to the surface of the spoon, and not tilted forward. This position of the handle will not interfere with the design of the edges of the print. If on the lower jaw the alveolar part is significantly atrophied and the spoon turned out to be narrow, then the handle is made wider, almost to the premolars: with such a handle, the doctor's fingers will not deform the edges of the impression when they hold it on the jaw

After the plastic has hardened (10-15 minutes), the spoon is removed from the model and processed with cutters and carborundum heads (an individual spoon is not polished), making sure that the edges of the spoon correspond to the boundaries marked on the model. The thickness of the edge of the spoon must be at least 1.5 mm, because with a thinner edge, it is difficult to obtain the volume of the edge of the print.

An individual spoon can be made from the base plastic by polymerization. To do this, the heated wax plate is pressed tightly over the model, giving it the shape of an impression spoon, the excess wax is cut off with a spatula along the marked boundaries. The wax form of the spoon is plastered into the cuvette in the reverse way and the wax is replaced with plastic.

When making a spoon from AKR-P plastic, standard plates are softened in hot water and crimped according to the model. The excess is cut off with scissors after softening the corresponding area. The handle is made from scraps of material and glued to the spoon with a hot spatula (plastic melts and welds from heat).

Individual spoons made of plastic are hard spoons. They can be used, as well as thermoplastic spoons, for taking compression impressions.

functional impression It is customary to call an impression that reflects the state of the tissues of the prosthetic bed during any movements of the lips, cheeks, tongue. For the first time, the method for its preparation was developed by Schrott in 1864.

Impression classification.

The most popular classification of impressions according to E.I. Gavrilov. It was based on the following basic principles.

1. The principle of the sequence of laboratory and clinical techniques for the manufacture of prostheses. On this basis, prints are preliminary (indicative) and final. Preliminary impressions are taken with a standard spoon. They are used to cast diagnostic models of the jaws, which allow studying the relationship of the dentition, alveolar ridges of the edentulous jaws, the relief of the hard palate and other features that are important for making a diagnosis, drawing up a plan for preparing the oral cavity for prosthetics and the plan for prosthetics itself. The same technique allows you to determine approximately and produce individual spoon . A working model is cast from the final impressions.

2. A method of designing the edges of the impression, allowing the prosthesis to have a closing circular valve, providing one or another degree of its fixation. Accordingly, there are anatomical and functional impressions .

According to the method of decorating the edges of E.I. Gavrilov subdivides functional impressions formatted with:

A) passive movements;

B) chewing and other movements;

C) functional tests.

between anatomical and functional impressions no clear boundary can be drawn. As such, there are no purely anatomical impressions. Receiving an impression with a standard spoon, when forming its edge, functional (though not sufficiently substantiated) samples are always used. On the other side, functional impression represents a negative display of anatomical formations (palatine ridge, alveolar tubercle, transverse palatine folds, etc.) that do not change their position during movements of the lower jaw, tongue and functions of other organs. Therefore, it is perfectly natural that functional impression has signs of anatomical, and vice versa.

3. The degree of pressure or the degree of squeezing of the mucous membrane.

According to the degree of its squeezing, functional impressions are divided into:

1) compression or obtained under pressure, which can be arbitrary, chewing, dosed;

2) differentiated (combined);

Individual spoons.

Under any clinical conditions, only functional impression individual spoon.

Customized spoons can be made from:

1) metal (steel, aluminum) by stamping;

2) plastics:

A) basic (fluorax, ethacryl, yarocryl) polymerization method;

B) fast-hardening (redont, protacryl) by free molding;

c) standard plastic plates AKR-P;

D) light-curing plastic;

3) solar-cured materials with polymerization in special chambers or using a solar lamp;

4) thermoplastic impression masses (Stens);

5) wax.

individual spoons are made in the laboratory or directly with the patient.

Making an individual spoon from plastic in the laboratory.

In this case, an anatomical cast is taken with a standard spoon and a plaster model is cast on it. On the model, the dental technician draws the boundaries of the future individual spoon.

From the foregoing, it can be seen that both on the upper and on the lower jaw individual spoon border passes 2-3 mm less than the boundaries of the prosthesis. This is done in order to leave room for the impression material. The displaced impression material forms the edges of the impression. And, conversely, the distal borders of the tray should be larger than the borders of the prosthesis so that the anatomical formations that are the guidelines for the distal edge of the prosthesis are well imprinted when the impression is taken.

After applying the borders, the dental technician covers the model with Isokol insulating varnish and proceeds to making a custom spoon from quick-hardening or basic plastic.

For making a custom spoon from quick-hardening plastic, the required amount of material is kneaded to the dough-like stage and a plate is made from it in the shape of the upper or lower jaw, which is crimped on the model along the outlined boundaries. Then, from small pieces of plastic "dough", a handle is made perpendicular to the surface of the spoon, and not tilted forward. This position of the handle will not interfere with the design of the edges of the print. If on the lower jaw the alveolar part is significantly atrophied and the spoon turned out to be narrow, then the handle is made wider, almost to the premolars: with such a handle, the doctor's fingers will not deform the edges of the impression when they hold it on the jaw

After the plastic has hardened (10-15 minutes), the spoon is removed from the model and processed with cutters and carborundum heads ( individual spoon do not polish), making sure that the edges of the spoon correspond to the boundaries marked on the model. The thickness of the edge of the spoon must be at least 1.5 mm, because with a thinner edge, it is difficult to obtain the volume of the edge of the print.

individual spoon can be made from the base plastic by polymerization. To do this, the heated wax plate is pressed tightly over the model, giving it the shape of an impression spoon, the excess wax is cut off with a spatula along the marked boundaries. The wax form of the spoon is plastered into the cuvette in the reverse way and the wax is replaced with plastic.

Individual plastic spoons are hard spoons. They can be used, as well as thermoplastic spoons, for taking compression impressions.

Advantages and disadvantages of individual plastic impression trays. Plastic spoons are rigid, do not deform in the oral cavity, but, like any laboratory-made spoons (in two visits), they require subsequent correction in the oral cavity. In addition, spoons made in this way give a modified image of soft tissues, since they are compressed and stretched during the anatomical impression.

Wax individual spoons for the upper and lower jaw

Personalized wax spoons can be made both in the laboratory and directly in the oral cavity. Wax spoons according to the CITO method are made in one visit directly on the jaw of the prosthetist. Such spoons are more accurate than individual ones made from an anatomical cast, because they display the soft tissues of the prosthetic bed at rest. The disadvantage of such spoons is that soft wax is deformed during fitting in the oral cavity and when taking an impression (it cannot withstand pressure), therefore, a wax spoon can only be used to remove decompression impressions. individual spoons , regardless of what method and what material they were made of, should be fitted in the oral cavity. A properly fitted spoon sticks to the jaw and does not lag behind it with the movements of the lips and cheeks. In our country, widespread method of fitting individual spoons using Herbst functional tests.

Five samples are used on the lower jaw:

1) swallowing and wide opening of the mouth;

2) movement of the tongue to the sides along the red border of the upper and lower lips;

3) touching the tip of the tongue to the cheeks with a half-closed mouth;

4) movement of the tip of the tongue forward beyond the lips towards the tip of the nose;

5) stretching the lips forward.

Three samples are used on the upper jaw:

1) wide mouth opening;

2) suction of the cheek;

3) displacement of the lips forward (stretching).

Getting a functional impression.

After fitting an individual spoon, they begin to obtain a functional impression.

Taking an impression consists of the following steps:

1) fitting of an individual spoon;

2) applying the impression mass on a spoon;

3) the introduction of a spoon with a mass into the oral cavity;

4) forming the edges of the impression and conducting functional tests;

5) removal of the impression and its evaluation.

It should be taken as a rule that functional impression, providing good fixation of the prosthesis, can only be obtained if the anatomical impression reflects all the structures of the prosthetic field and some functional features of the tissues surrounding the prosthetic bed. Upon receipt functional impression they are only specified.

There are unloading or decompression and compression impressions.

Usually, the value of a compression or unloading impression is associated with the fixation of the prosthesis and its effect on the mucous membrane of the prosthetic bed. However, the value of one or another technique for taking an impression is determined by the influence of the prosthesis on the course of the process of atrophy of the alveolar process.

Unloading (decompression) impressions obtained without pressure or with minimal pressure of the impression mass on the tissues of the prosthetic bed.

The disadvantage of the unloading impression is that the buffer zones of the hard palate are not subjected to compression, and all the pressure from the prosthesis is transferred to the alveolar process, increasing its atrophy.

When receiving a decompression impression, the impression material must reflect without distortion every detail of the oral mucosa so that the microrelief of the prosthesis base exactly matches the surface structure of the prosthetic bed. Therefore, such impressions can be obtained only with the help of impression masses that have a high fluidity and do not require much effort to remove the impression. Such masses include low viscosity silicone pastes: exaflex, xanthoprene, alfazil, as well as zinc oxide eugenol pastes. An impression obtained using liquid gypsum (according to Brahman) usually provides just such a perception of the relief of the surface of the tissues of the prosthetic bed. Some authors believe that if several holes are drilled in the impression tray to drain excess impression material, then the pressure of the impression mass on the mucous membrane can be reduced.

It is known that the fixation of prostheses made from decompression impressions is weak, but they can be used if there are certain indications.

These indications include:

1) significant or complete atrophy of the alveolar processes and mucous membrane;

2) increased sensitivity of the mucous membrane;

3) uniformly pliable mucous membrane of the prosthetic bed.

Compression impressions designed to take advantage of mucosal compliance, so they are removed at high pressure to compress the buffer zones. When talking about a compression impression, they first of all mean the compression of the vessels of the prosthetic bed. The decrease in tissue volume, its vertical compliance are directly dependent on the degree of filling of the vascular bed. The use of compression impressions is recommended in the presence of a loose mucous membrane with good compliance.

A prosthesis made according to a compression impression does not load the alveolar ridge; outside of chewing, it relies only on the tissues of the buffer zones, like on pillows. When chewing under the influence of chewing pressure, the vessels of the buffer zones are emptied of blood, the prosthesis settles somewhat and transfers pressure not only to the buffer zones, but also to the alveolar part. Thus, the alveolar process is unloaded, which prevents its atrophy.

A prosthesis made according to a compression impression has a good fixation, because the pliable mucosa of the valvular zone is in closer contact with the edge of the prosthesis.

The compression impression is taken under continuous pressure. , providing compression of the vessels of the mucous membrane of the hard palate and their emptying. To obtain such an impression, certain conditions must be met:

1) you need a hard spoon;

2) the impression must be taken with a low flow mass or a thermoplastic mass;

3) compression should be continuous, stopping only after the mass hardens. Continuity can be ensured by hand effort (voluntary pressure). But it is more convenient and correct to take a compression impression under the chewing pressure of the muscles that lift the lower jaw, i.e. under bite pressure, which is created by the patient himself, or with the help of special devices that allow you to create a strictly defined pressure (metered) taking into account the individual characteristics of the tissues of the prosthetic bed and chewing muscles.

For obtaining a functional impression use thermoplastic masses, such as Dentofol, Otrocor, Orthoplast, etc.

The convenience of using thermoplastic masses is explained by the following properties:

1) they have an extended plasticity phase, which makes it possible to carry out functional tests necessary to obtain a high-quality impression;

2) during the removal of the impression, they always have the same consistency;

3) they do not dissolve in saliva;

4) evenly distribute pressure;

5) allow you to repeatedly enter the impression into the oral cavity and carry out correction, because new portions of the mass merge with the old portions without deforming the impression.

However, thermoplastic masses have certain disadvantages. These include: inaccurate print due to low fluidity; deformation in the presence of retention points. When cooled with water, they harden unevenly and may deform when removed from the oral cavity.

It should be recognized that when using the above methods of obtaining an impression, in some cases it is not possible to provide a complete functional reflection of the prosthetic field. The tissues of the prosthetic field and the active muscles surrounding it are not the same in relief, relative volume, physiological status during chewing or talking, as well as during the day. The physical and emotional state of a person also has a great influence on the state of the prosthetic bed and the muscles surrounding it. Whatever method of taking the impression is used, further adaptation of the basis of the prosthesis to the tissues of the prosthetic field, the ratio of the dentition and the force of masticatory pressure, as well as the adaptation of the patient and the fitting of the prosthesis for a certain time, is necessary.

The wide variety of clinical conditions encountered for prosthetics necessitates the use of a differentiated impression. One should proceed from the general position that there is no single method shown in all cases. In this regard, the method of obtaining an impression in each case must be chosen taking into account the age of the patient, the constitutional and individual characteristics of the tissues of the jaws, i.e. in all cases, a differentiated approach is needed. In cases where the tissues of the prosthetic bed in different areas are not the same in their relief and structure, the biophysical properties of each of the elements of the prosthetic bed should be taken into account. When taking an impression, tissues with pronounced spring properties should be under greater load, while tissues of unloaded zones (in the region of the torus, incisive papilla, etc.) should not be excessively loaded.

Selective pressure on the underlying tissues, depending on their anatomical and functional features and biophysical properties, may be important in connection with the need to prevent premature atrophy of the soft and bone tissues of the edentulous jaws by redistributing the masticatory pressure of the prosthesis base.

Therefore, depending on the anatomical and physiological features of the prosthetic bed, it is possible to obtain a display of the mucous membrane in various functional states. At the same time, unloading casts are recommended to be obtained with a thin, atrophic and excessively pliable ("dangling" comb) mucosa. Compression casts are indicated for loose, well-compliant mucosa. The best effect can be achieved only by using differentiated casts obtained with varying degrees of compression of the mucous membrane, taking into account its compliance in different parts of the prosthetic bed.

Requirements for a functional impression:

1) have an accurate and clear imprint of the surface of the mucous membrane of the prosthetic bed without areas and pores washed out by saliva;

2) to have a uniform thickness of the edge and the layer of impression material of the bases of the gaps of the spoon;

3) have an accurate display of the "A" line and blind pits;

4) the edges of the print must be smooth and rounded;

5) the entire impression must be removed from the oral cavity.

Casting of working models.

After receiving the impression, they begin to evaluate it: they check whether the material is pressed in any areas, whether the edges are well-formed, what is their volume. Air pores are not allowed. Then the suction force of the impression is determined. To do this, an impression is introduced into the oral cavity, pressed against the prosthetic bed, and by the handle of the spoon they try to tear it away from the bed. If this is difficult, then this means that the fixation is good. In the event that all requirements are met, the impressions are transferred to the laboratory for further work.

To prevent violation of the valve zone on the model during its opening, the edges of the imprint should be edged. It is carried out as follows. A strip of wax 2-3 mm thick and 5 mm wide is layered 3-5 mm below the edge of the impression. After that, the model is cast in the usual way. The dental technician, cutting off the model, removes excess plaster only within the edging, thereby not violating the sections of the mucous membrane of the transitional fold, in which the edge of the impression was placed. After receiving the model, the wax is removed, and along its edge, a clear functionally designed border and a volumetrically reproduced valve zone remain on the model. If the integrity of the transitional fold is violated, modeling the edge of the prosthesis in accordance with the valve zone becomes impossible, because the marginal closing valve will have defects, which will lead to a violation of the fixation of the prosthesis.

The manufacture of plaster models of edentulous jaws is slightly different from the manufacture of those for removable dentures with partial defects in the dentition. Models with edentulous jaws are specially engraved.

Existing tubercles and nodules are removed from plaster models with a spatula. They are formed from the presence of small bubbles on the surface of the cast. After a general check, the model of the upper jaw is prepared for the creation of a peripheral valve on the palatal surface.

A small layer of gypsum 0.5-1.0 mm deep and of various widths is engraved with a spatula in the transition area of the hard palate into the soft palate. Such an engraving of the model leads to the formation of an elevation at the border of the prosthesis, which is immersed in a pliable tissue. The pressing of soft tissues on the valve zone corresponds to the creation of a palatal valve for the prosthesis on the upper jaw.