Individual impression trays can be made in two ways: direct and indirect.

A direct method is called a method in which an impression tray is made from wax for bases at once directly on the patient's jaw.

Indirect is a method in which a usual anatomical cast from plaster is first removed from the patient's jaw using a standard metal spoon. A model is cast from this cast, and a spoon is made from plastic or other solid material from the model in the laboratory.

However, individual trays made from anatomical impressions do not provide an accurate representation of the moving soft tissues surrounding the prosthetic base.

A standard metal spoon is always larger than the jaw; it is clear that the outer edges of such a spoon, as well as excess impression material, shift and stretch the movable soft tissue and do not display them functional state... An individual tray made from such an impression or impression requires significant edge correction. It must be said that such a correction of an individual spoon sometimes takes much more time from an orthopedic surgeon than the one-step production of an individual spoon from wax directly on the patient's jaw.

The technique of making an individual impression tray from wax was developed by G.B. Brakhman at the Central Institute of Traumatology and Orthopedics. This technique is not difficult, but it requires skill and experience.

On average, it takes 10 to 15 minutes to make such a spoon. It should be noted that although hard wax is used for this purpose, the possibility of deformation of the spoon during the taking of the impression is not excluded. Some doctors, in order to prevent deformation of the spoon during the taking of the impression, recommend gluing a metal wire into the upper spoon or coating its outer surface with plaster. It is recommended to form a wax roll on the lower tray in the center of the alveolar process. A spoon is considered ready if it does not move when moving with hands and is well held on the jaw.

Despite the fact that an individual wax spoon has a number of advantages, it also has significant drawbacks that made it necessary to resort to its modification.

The disadvantages of a custom wax spoon are as follows:

• 1) wax softens at a temperature of 37-38 °, which corresponds to the temperature of the oral cavity; as a result of this, unnoticed by the doctor, a deformation of the spoon may occur;
• 2) in the presence of anatomical retention on the jaw, the plaster cast breaks very often when it is removed from the oral cavity, since the cast cannot be correctly placed in a deformed wax spoon.

Considering the indicated disadvantages of an individual wax spoon, BR Vainshtein suggested making such a spoon from a tougher material, for which the wax spoon is plaster of paris in a cuvette and replaced with plastic (Fig. 24).

A number of the following requirements are imposed on an impression or an impression from a toothless jaw:

• 1) the impression must be distinct, without a coating of mucus or saliva, not porous, it must not be squeezed until the impression tray is visible;
• 2) place of transition hard palate in soft (line A) must be clearly displayed on the impression; this is controlled by obtaining an imprint of two point depressions, which are located on the border of the transition of the hard palate to the soft palate;
• 3) the edges of the impression should be well processed, smooth and should follow the contours of the transition fold (neutral zone);
• 4) the cast must be removed from the mouth intact; if a small piece of plaster breaks off from the edge of the cast, it does not matter, but if the plaster is more severely broken, the cast is unusable.

When making prostheses for a patient with complete loss of teeth, in addition to anatomical ones, functional impressions are required.
A functional impression is an impression obtained using an individual tray, the edges of which are shaped using functional tests.
Custom spoons can be made from a variety of materials. They are made at the dental chair or laboratory way.
Most spoons are currently made in the laboratory.
For this purpose, according to the anatomical impression obtained) a standard spoon, make a plaster model and draw the boundaries of the spoon within the transition fold (at the deepest place on the model).
Billets made of AKR-P plastic are softened in hot water or over a burner flame, placed on the model and pressed tightly 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 the scraps for the lower spoon, gluing it to the spoon with a strongly heated spatula.
The clinic showed that the spoons made of AKR-P plates are deformed during impression taking and have thin edges.
The spoon can be made from any fast-hardening plastic... The plastic dough prepared for these purposes is rolled out to a thickness of about 2 mm, a shape similar to AKR-P blanks is cut out of the plate, and compressed according to a model covered with a layer of "Izokola". To harden the plastic, the 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 pneumopolymer.
Much faster, you can make a fairly accurate individual spoon by pressing the speed
hardening plastic or blanks from it in the apparatus of E. Ya. Vares or Yu. K. Kurochkin.
A spoon of uniform thickness, precise and durable is obtained if it is prepared through a wax composition. For this purpose, a wax plate, compressed according to the model within: within the boundaries and trimmed, is glued along the perimeter to the model and gypsum into the cuvette in the opposite way. After melting the wax and insulating the plaster mold, the base or fast-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 ridge or alveolar cusps, an individual spoon is prepared with a second layer of wax. The first layer of base wax, compressed over the model and trimmed within the drawn borders, is covered with a thin layer of petroleum jelly. Apply a second layer of wax, squeeze, trim. A 10x10 mm vertical handle is created on the lower spoon in the front area.
The workpiece from the second layer of wax is removed from the model and plaster cast, 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.

Stages of obtaining functional impressions, fitting an individual rigid spoon.
Functional prints were first proposed by Schrott (in 1864). Metal spoons were made for both jaws. Springs were soldered to the spoons, which fixed them on the prosthetic field. Heated gutta-percha was applied in a spoon and the patient was applied for 15 - 20 minutes. made various movements of the jaw, moved his lips, cheeks and tongue.

Motte (1897) made prostheses from anatomical impressions. I applied a layer of gutta-percha and let the patients use it for 1 - 2 days.

Methods for making individual spoons.

Making an individual spoonfrom self-hardening plastics (Karboplast, Protakryl, Redont) consists in the preparation of a plastic dough, the formation of plates of a certain shape and thickness and their compression of a gypsum model, previously coated with Isokol insulating varnish, manually or using the above-mentioned apparatus. After polymerization of the plastic (10-15 minutes), the spoon is removed from the model and processed with cutters and carborundum heads, observing the observance of the outlined boundaries. The thickness of the edge of the spoon should be at least 1.5 mm, since with a very thin edge it is difficult to achieve sufficient volume of the impression.

If it is supposed to remove a unloading functional cast with plaster, for example, with a thin, atrophic mucosa or there are canopies on the alveolar process that interfere with the imposition of a spoon, then it is prepared according to the so-called second layer. After the wax reproduction of an individual spoon is compressed and formed, it is smeared with petroleum jelly and compressed with a second layer of wax, which is replaced with plastic.

The first layer serves to create a space between the mucous membrane of the prosthetic bed and the spoon, in which the impression mass is located, that is, gypsum, since a very thin layer of it can crumble. Currently, this technique has lost its significance, because there are a large number of impression materials (silicone, thiokol, zinc oxide guaiacolopia), which do not crumble and allow obtaining an impression with a minimum thickness, so there is no need to create space in advance. The next step is fitting an individual spoon.The spoon is fitted to the upper toothless jaw according to the following plan.

First, the frenum of the lip, the lateral strands are released, creating recesses for them along the edge of the spoon. Then check the border behind the alveolar tubercles, focusing on the place of attachment to upper jaw pterygoid fold, which should not be covered with a spoon. Simultaneously, the "A" line and the topography of the blind holes are revealed, for which the latter are most often marked with a chemical pencil and a spoon is placed on which they are imprinted. It should be noted that Herbst's tests are not often used to clarify the boundaries of the spoon on the upper jaw.

When fitting a spoon on the upper jaw, it should be taken into account that the border of the prosthesis from the vestibular side should cover the pliable mucous membrane, squeezing it somewhat and being 1-2 mm below the transitional fold, contact with its dome (movable mucous membrane) and have a concave vestibular surface. With this configuration of the edge of the prosthesis, the cheek will fit tightly, and the fixation will be better, since this prevents the flow of air under the prosthesis.

The position of the impression along the "A" line is important for fixing the prosthesis. At this point, it should end on the soft palate, passing to it by 1-2 mm. The soft palate should be captured in an elevated position. If this condition is not met, the impression will be taken with the sky down.

In this case, the prosthesis will be poorly fixed during eating and talking, since the soft palate rises, allowing air to pass under the prosthesis. In order to squeeze out the soft palate when taking an impression, a strip of thermoplastic mass is applied to the palatal edge of the spoon, you can wax 4-5 mm wide and 2-3 mm thick. However, it should not overlap the edge of the spoon in the place where it can push back the pterygo-maxillary fold, that is, the alveolar tubercles should be free. Then the spoon is inserted into the mouth and pressed against the palate with the mouth half-closed. When the mass hardens, the spoon is removed from the mouth.

Fitting an individual spoon to the lower jaw also begins with the release of the frenum of the lip and tongue, as well as the lateral cords by creating notches in the edge of the prosthesis. This can be done with a narrow fissure bur, discs, wheel head. The mucous tubercles (tuberculum mucosum) serve as a reference point for determining the distal border. They are covered with a spoon partially or completely, depending on their shape, localization, consistency, the presence or absence of pain on palpation. There is no consensus on this issue and it is decided individually. On the lingual side in the lateral regions, the spoon should overlap the inner oblique line if it is round and reach it when acute form, but its posterior lingual edge must be in the muscleless triangle. In the presence of exostoses in anterior section the alveolar process, the spoon overlaps them, leaving free the excretory ducts of the hyoid glands.

On lower jaw make prostheses with boundaries that exactly fill the volume of the transition zone. If possible, they should cover the retromolar and sublingual spaces. If it is not possible to achieve functional suction of the prosthesis, then the expansion of the boundaries is justified, since at the same time the pressure per unit area of \u200b\u200bthe prosthetic bed decreases.It should be noted that the question of the possibility of expanding the base in the anterior section should be decided strictly individually. The expansion zone can be found as follows. The patient is asked not to strain the lips and keep the lower jaw at rest. Then the doctor puts the index finger in the middle of the lower lip from the inside, and thumb - outside and asks the patient to tighten their lips. By such palpation, the area of \u200b\u200bleast tension is revealed, which is usually oval in shape, with a vertical size in the center of 1.5-2.0 mm and, gradually narrowing, ends between the canines and the first premolars, where the muscle node -modiolus is located. The lower border of this area is 0.5 mm above the chin-labial fold, and the upper one is 2-3 mm below the red border of the lip. The described zone is not differently expressed in different people, depending on the tone of the chin, circular muscles of the mouth and atrophy of the alveolar process. Thus, it is more necessary to expand (thicken) the basis with significant atrophy of the alveolar ridge and weak tone of these muscles.

Appearance individual spoon for upper and lower jaws.

STEPS IN OBTAINING FUNCTIONAL PRINTING

Assessment of the anatomical and topographic features of the prosthetic bed
Obtaining a preliminary impression and a model for the manufacture of an individual rigid spoon
Preparing a preliminary model, making an individual spoon
Getting a functional impression

Topic # 5: Herbst Samples
Herbst samples. Neutral zone, borders, their definition.
Herbst probes when taking a functional impression are required to form volumetric edges and display the valve zone. Tests are carried out for the design of the edges of the functional impression with a silicone base mass, polyvinylsiloxane mass, wax or thermomass.

Herbst samples

FUNCTIONAL TRIALS	CORRECTION ZONES
LOWER JAW:
1. Swallowing and wide mouth opening.	The edge from the place behind the tubercle to maxillary-hyoid line. The edge from the tubercle to the place where it will be stand the second molar.
2. Swipe the tongue across the red border of the lower lip.	The edge along the jaw sublingual line.
3. Touch the tip of your tongue to cheeks with a half-closed mouth.	The edge of the hyoid region on distance 1 cm from the midline.
4. Stick out your tongue towards the tip of the nose.	Edge at the frenum of the tongue.
5. Active movements of facial expressions musculature, lip extension forward.	Edge between the canines and in the area buccal-gingival cords.
UPPER JAW:
1. Wide mouth opening.	The edge from the h / h mound to the buccal gingival cords.
2. Suction of the cheeks.	The edge in the cheek-gingival area heavy.
3. Pulling the lips.	The edge is in the anterior section.

Valve zone - areas of the movable mucous membrane involved in the formation of the closing valve along the edge of the prosthesis.
NEUTRAL ZONE - passively mobile (well-compliant) mucous membrane, which spreads in the form of a strip of uneven width along the vestibular surface of the upper and lower jaws, along the lingual surface of the lower jaw and along the "A" line.

FROM chemistry of mucosal topography.

a - transitional fold of the vestibule of the oral cavity;

6 - neutral zone;

c - motionless mucous membrane of the alveolar process.

Transitional fold with complete absence of teeth (diagram)

1 - actively mobile mucous membrane;

2 - passively mobile (neutral zone);

3 - motionless.

BOUNDARIES OF THE NEUTRAL ZONE
On the one hand, the place of transition of an active-mobile mucous membrane into a passive-mobile one, that is transition fold, which corresponds to the points of attachment of the mimic and chewing muscles to the jaws;

On the other hand, it is the place where the passively mobile mucosa transitions to the immobile one.

Thus, the transitional fold and the neutral zone represent different anatomical structures. Nor should these zones be confused with the concept of "valve zone".

Neutral zone width:

In the area of \u200b\u200bfrenulum, lips and tongue, buccal-gingival and pterygo-maxillary folds and palatine fossa does not exceed 1-3 mm,

In the intervals between these formations it reaches 4-7 mm.

The mucous membrane in the neutral zone has a well-developed submucous layer in the form of a loose connective tissuein which there are no muscle fibers. It can mix horizontally and vertically, gather in folds, but all these movements are passive, arise under the influence of external force (this can be a food lump or foreign body).
DETERMINATION OF THE BOUNDARIES OF THE NEUTRAL ZONE
The neutral zone is easily determined by pulling the lips, cheeks behind skin and at the same time, the upper (lower on the lower jaw) border is clearly visible - a transitional fold, and when the mucous membrane is pulled back - the border with the immobile mucosa. It is more difficult to determine the border of the neutral zone along the line "A", since, and the immobile mucous membrane of the hard palate smoothly passes into the mucous membrane of the soft palate. The palatine fossa and the line connecting the points at the bases of the alveolar tubercles of the upper jaw serve as landmarks for determining this zone.

The anterior border of the neutral zone passes through these points and fossa, and in the intervals between them it deviates anteriorly, by 2-5 mm along the course of a weakly expressed tortuous transverse narrow groove, which is a projection of the transverse ridge of the palatine bones.

The distal border overlaps the palatine fossa by 1.5 - 2 mm.

The neutral zone in all these areas is completely overlapped by the base of the prosthesis.

Topic number 6: Justification of the choice of the impression material for obtaining

functional casts
Classification of impressions by E.I. Gavrilov.

Technique for obtaining functional impressions.
SCHEME: CLASSIFICATION OF PRINTINGS BY E. I. GAVRILOV "

FUNCTIONAL PRINTS
A functional impression is an impression that reflects the state of the tissues of the prosthetic bed during function. Functional impressions can be: compression,obtained with finger pressure or bite pressure of the patient; decompression(unloading), obtained without pressure on the tissues of the prosthetic bed; differentiated,which provide a selective load on certain areas of the prosthetic bed, depending on their functional endurance.

Compression impressions should be used mainly on the lower jaw when the doctor diagnoses the presence of a weak, thinned mucous membrane. Compression impressions allow to obtain a relief of the prosthesis base, which facilitates the transfer of masticatory pressure over a large area bone base prosthetic bed. This is a positive factor that contributes to the preservation of the bone base and prevents increased atrophy. bone tissue from excessive chewing pressure. But in the presence of an area with a pliable mucous membrane, it plays the role of a compressed spring that drops the prosthesis when talking and opening the mouth. Also, compression impressions are used for loose and pliable mucous membranes, when it is important to accurately display the bone base of the prosthetic bed.

Low flow rates are well suited for compression impressions, with relatively high degree viscosity and plasticity impression materials (thermoplastic, silicone masses with a low degree of fluidity).

Compression impressions are taken when finger pressure at dosed hardware pressure and pressure bitewhen teeth are partially preserved on one of the jaws.
Decompression(unloading) impressions are shown with a pliable, loose and mobile mucous membrane. In this case, the basis of the prosthesis has a relief of an uncompressed mucous membrane, which has a positive effect on fixing the prosthesis during speech function and rest. Therefore, this kind of bases of plate prostheses are shown to people whose work is closely related to speech. In these circumstances, it is important to take into account that the chewing pressure will be unevenly distributed, since the macrorelief of the mucous membrane and the base of the prosthesis will not correspond to the relief of the bone base. Consequently, the chewing pressure, compressing less pliable areas of the mucous membrane, will be transmitted to the alveolar bone in certain areas, which will lead to overload and, as a result, to its increased atrophy.

For the unloading impression, impression materials with a high degree of flow are used. The most acceptable are additive polyvinylsiloxane and condensation silicone and limited zinc-eugenol and thiokol masses.
Differentiated or combined impressions are able to compress the malleable and not overload the low-compliant areas of the prosthetic bed mucosa. Under such conditions of obtaining an impression, the base of the prosthesis is not reset during the speech function and interacts well with the hard tissues of the prosthetic bed, providing an even distribution of chewing pressure.

In other words, when obtaining a functional impression with an edentulous upper jaw, it is recommended to load areas of the mucous membrane with a well-pronounced vertical compliance, and to unload areas with a thinned, atrophied mucous membrane with a minimum pressure of the impression material, i.e. get a differentiated impression. Consequently, the impression must be obtained using two different materials with different degrees of flow. The technique for obtaining differentiated impressions is quite diverse, but the basis for obtaining the required shape of the basis of the prosthesis should be an impression obtained with a silicone or two-layer alginate mass. The principle of taking an impression consists in loading the mucous membrane with the first low-flow layer of the impression material, then mechanically removing the impression mass from the surface of the individual tray in the areas corresponding to the zones of the pliable mucous membrane and, finally, obtaining the second layer with a much more fluid mass.
For a clearer display of the relief of the prosthetic field and minimizing errors in technical steps modern achievements dentists in full removable prosthetics dictate the need to take two or even more functional impressions, each time making an individual spoon that more closely matches the prosthetic bed.

REFERENCE BASIS DIAGRAM

Introduction

To create an optimal closing valve, the neutral zone must be displayed as clearly as possible during the function on the model. In accordance with current trends orthopedic dentistry, this can be done only with the help of an individual spoon, which is made according to an anatomical model, and its edges can be slightly lengthened. To accurately match the boundaries of the spoon to the boundaries of the prosthetic field, it is adjusted. This is the first step in taking a functional impression. Only after carefully carrying out all the stages can one count on the success of prosthetics for a fully edentulous patient.

Individual spoons. Methods for making an individual spoon. Clinical and technical features of the manufacture of individual spoons

Requirements for an individual spoon

• The edge of the spoon must be at least 1.5 mm thick
• The edges of the spoon should completely cover the prosthetic bed, without creating compression of its individual areas
• Borders of individual spoons:
• From the vestibular side on the upper and lower jaw, the border of the spoon does not reach the transitional fold by 2-3 mm, bypassing the mucous cords and bridles .
• The distal border in the upper jaw overlaps the maxillary tubercles and extends beyond line "A" by 2-3 mm.
• · On the lower jaw, the distal border passes behind the mandibular mucous tubercles and passes into the sublingual region, overlapping the linea mylohyoidea and bypassing the frenum of the tongue, not reaching the lower line of the sublingual space by 2-3 mm.

Methods for making a custom spoon

• Manufactured from self-curing acrylic plastic on model
• Compression pressing method
• Injection molding method
• Vacuum pressing method
• Manufactured from standard light-curing polymers

Method of making an individual spoon from self-hardening acrylic resin on a model

Self-hardening plastics of domestic production

Compression pressing method

The material to be formed is placed in a mold and compressed with a counter stamp:

Stages of making an individual spoon by compression pressing

Disadvantages of the compression molding method

• · Significant time consumption and high consumption of materials.
• · At the end of molding, no pressure is applied to the base material in the mold. Therefore, it is not possible to compact the plastic in order to reduce its shrinkage during the polymerization period and eliminate the appearance of pores.
• During the convergence stamp and counterstamp, excess material is squeezed out between them and prevents their contact, forming a burr. For example, when plastering dentures in a cuvette, this leads to overestimation of bite, because artificial teeth, which are in the counter-stamp, figuratively speaking, do not return to the previous level, but remain above it by the thickness of the burr.
• For the same reason clasps are displaced, if they were converted into a counterstamp during plastering.

Injection molding method

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

Customized spoons can be made from:

1) metal (steel, aluminum) by stamping;

2) plastics:

a) basic (fluorox, ethacryl, yarokryl) by polymerization;

b) fast-hardening (redont, protacryl) by free forming;

c) standard plastic plates AKR-P;

d) light-curing plastic;

3) helium-curing materials with polymerization in special chambers or using a heliolamp;

4) thermoplastic impression materials (Stens);

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

Manufacturing of an individual plastic spoon in a laboratory way.

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

On the upper jaw, the border of the spoon runs from the vestibular side along the transitional fold, not reaching the very deep point its vault by 1-2 mm. From the distal side, it overlaps the maxillary tubercles and runs along the "A" line behind the palatine fossa by 1-2 mm.

On the lower jaw, the border of the spoon runs from the vestibular side along the transitional fold, not reaching 1-2 mm to the deepest point of its arch, while bypassing the cords and the frenum 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 (nonmuscular triangle), not reaching the deepest place of the hyoid space by 1-2 mm and bending around the frenum of the tongue.

From the above, it can be seen that on both the upper and lower jaw, the border of the individual tray is 2-3 mm less than the borders of the prosthesis. This is done so that there is room for the impression material. The extruded 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 in order for the anatomical formations, which are the landmarks of the distal edge of the prosthesis, to be well imprinted when taking the impression.

After drawing the borders, the dental technician covers the model with Isokol insulating varnish and starts making an individual spoon from a quick-hardening or basic plastic.

To make an individual spoon from fast-hardening plastic, knead the required amount of material to the dough-like stage and make a plate out of it in the shape of the upper or lower jaw, which is squeezed on the model along the outlined boundaries. Then from small pieces plastic "dough" make the handle 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 is 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 (the individual spoon is not polished), making sure that the edges of the spoon correspond to the boundaries marked on the model. The edge of the spoon must be at least 1.5 mm thick, because with a thinner edge, it is difficult to obtain volumetric edge of the print.

An individual spoon can be made from base plastic by polymerization. To do this, the heated wax plate is tightly squeezed according to 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 mold is plaster of paris into the cuvette in the reverse way and the wax is replaced with plastic.

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

Customized plastic spoons are hard spoons. They can be used, just like thermoplastic spoons, for taking compression impressions.