Gypsum is a large medical encyclopedia. Gypsum - Medical encyclopedia Gypsum use in medicine

Medical gypsum is a white powder with a density of 2.66 - 2.67 g/cm2 with increased water absorption. When combined with water, water enters into a chemical reaction with it (2), as a result of which the gypsum molecules again become dihydrous and the entire mass turns into a solid state. The gypsum hydration reaction is exothermic.

(2) (CaSO4)2 -H2O + 3H2O -> CaSO4 -2H2O + t°

The rate of hardening of gypsum depends not only on the conditions of firing the gypsum, but also on the ratio of water and powder, mixing time, water temperature, as well as the admixture of certain substances to the gypsum.

The ratio of water is calculated to 100 g of gypsum. For example, if 100 g of powder is mixed with 80 ml of water, then the ratio of water to powder (W:P) will be 0.8:1 (0.8), when mixing 100 g of powder with 45 ml of water, the W:P will be equal to 0. 45.

The W:P ratio is a very important factor in determining the physical and chemical properties of the final gypsum product. Along with mixing time, the W:P ratio affects the hardening time of the gypsum and its strength (Tables 4-2, 4-3).

Table 4-2. Influence of the ratio of water to gypsum powder (W:P) and mixing time on the hardening time of semi-aqueous gypsum*

The rate of hardening of gypsum is also influenced by the temperature of the water or solution used. Cold and hot water slow down, and water heated to a temperature of 37°C accelerates the hydration reaction (Sidorenko G.I., 1988).

Table 4-3. Influence of the ratio of water to gypsum powder (VP) and mixing time on the strength of semi-aqueous gypsum*

When using gypsum as an impression material, it is advisable to speed up the hydration reaction and reduce its strength. The hardening time of gypsum can be reduced by introducing catalysts. Most often, sodium chloride NaCl is used as a catalyst, which is added to water in an amount of 2.5-3% by weight. In addition to sodium chloride, potassium chloride KS1, potassium sulfate KSO4, sodium sulfate NaSO4, potassium nitrate KNO3 and a number of other salts can be used as catalysts. Additions of a catalyst make it possible to reduce the strength of gypsum by 2 times and reduce the binding time of the material by 3 times (compared to type II gypsum used for making models).

To obtain gypsum mass used as an impression material, it is necessary to mix the catalyst solution and powder in a ratio of 1:2 - 1:1.33 (B:P = 0.5-0.75)1. The preparation of plaster as an impression material is carried out in the following sequence (Fig. 4-3). A certain amount of catalyst solution is poured into a rubber flask and gypsum powder (4-3.1) is added to it in portions. Gypsum hydrolyzes and

Rice. 4-3. Preparation of plaster for making an impression.

having a density of 2.67 g/cm2, sinks to the bottom of the flask. The powder is added until a slight excess is formed above the surface of the water. When the gypsum is completely saturated with water, its excess is drained and the components are mixed until a homogeneous mass is formed (4-3.2). The preparation of gypsum is completed by thoroughly mixing the material using a spatula (4-3.3).

1 The ratio of water and powder must be specified separately for each batch of gypsum (taking into account grinding, composition and other properties).

Excess water in the gypsum material is undesirable, because, on the one hand, it lengthens the time for the onset of the initial setting period, since many hardening centers are formed, but they are located at a long distance from each other for a long time and the gypsum dough is therefore too liquid. When the centers of hardening come closer together, the setting period proceeds so quickly that the doctor does not have time to apply the dough to a spoon and introduce it into the oral cavity. On the other hand, an excess of water in gypsum dough also leads to the fact that there is a large amount of free water between the gypsum molecules that interact with water. After the water evaporates, pores form in its place, reducing the strength and quality of the gypsum part (G.I. Sidorenko, 1988).

The mixing time for impression plaster should be 1 minute. The prepared mass is applied to a pre-selected metal impression tray without

Rice. 4-4. The sequence of removing a plaster impression from the oral cavity

perforations. Working time is 2-3 minutes. After 4-5 minutes from the start of mixing, the impression is removed from the oral cavity (Fig. 4-4). First, the impression tray (4-4.1) is separated and removed, then the plaster is divided into parts. To do this, place the index finger on the vestibular edge of the impression in the area of ​​the chewing teeth and rotate part of the impression (4-4.2). After separating the first part, move the finger to another area and break off the next fragment of the impression. Chipping of the impression can be facilitated by cutting the plaster in the area of ​​the occlusal surface of the teeth. After removing the impression from the oral cavity (Fig. 4-4.3), its parts are installed in the impression chamber

spoon (Fig. 4-4.4). The spoon is wiped to remove pieces of plaster on the outer and inner surfaces. Remove small pieces of plaster from each part of the impression. Particular attention should be paid to cleaning the surface of the plaster from the side adjacent to the tray and along the fracture lines. When assembling parts of a plaster impression, first large pieces with impressions of the palate or lingual surface of the alveolar part of the lower jaw are placed in a tray. Other smaller fragments are sequentially attached to them, guided by the prints and fracture lines.

After all the pieces have been placed, the impression is assessed. When the impression is correctly assembled, its parts fit tightly to the tray, the fracture lines coincide exactly, without forming gaps (Fig. 4-4.5).

After assessing the impression, they begin to secure its parts using molten (boiling) wax (Fig. 4-4.6). Once on the plaster, the wax penetrates its pores and reliably glues the impression together.

Before casting the model, the plaster impression is kept for 8-10 minutes in a soap solution. This is done to prevent the material from bonding with the plaster of the model.

The disadvantages of gypsum include its low accuracy in displaying the microrelief of the tissues of the prosthetic bed, connection with the model material, empirical dosage of components, lack of elasticity after hardening and the inability to remove the material entirely from the oral cavity.

The only positive property of gypsum is the absence of shrinkage of the material after the impression is removed from the oral cavity and during its storage.

For a long time, gypsum was practically the only universal impression material. Currently, the medical arsenal has many new high-quality impression materials that have undeniable advantages over gypsum hemihydrate.

GYPSUM (Gypsum; CaSO 4 2H 2 O) is a mineral that is a crystalline hydrate of calcium sulfate. Widely distributed in nature, used in honey. practice (see Plaster technique). Pure crystalline gas is colorless and transparent; in the presence of impurities, it acquires gray, yellowish, brown, pinkish, or other colors. Density 2.3 g/cm 3, solubility in water 2.05 g/l (at 20°), in dilute hydrochloric and nitrogen solutions - higher. It occurs in nature in the form of gypsum dihydrate (CaSO 4 2H 2 O) and anhydride (CaSO 4). G. dihydrate, known as gypsum stone, serves as the main raw material for the production of gypsum binders. So-called Burnt g., widely used in surgical practice and dentures as a binding material, consists mainly of calcium sulfate hemihydrate (CaSO 4 0.5H 2 O). This is a thin white or grayish powder obtained by partially dehydrating natural gypsum stone by heating it to 120-130°. A characteristic feature of calcium sulfate hemihydrate is its ability, after mixing with water to a creamy consistency, to form a plastic dough that can turn into a non-plastic mass within a few minutes: the so-called. setting - hardening as a result of crystallization. The setting time of gypsum depends on the quality of the raw material, the fineness of grinding, firing conditions, the temperature of the mixture of burnt gypsum and water during mixing, the value of the water: gypsum ratio, and the duration and storage conditions of the raw materials. The hardening time can be adjusted with special retarding or accelerating additives. In dental practice, it is customary to use 3% solution of table salt or finely ground glycerin, which forms crystallization centers, to speed up setting, and to slow it down, use 3% solution of glycerin or dextrin.

A feature of burnt clay is that its volume increases during hardening, sometimes up to 0.5% (usually less - about 0.1-0.2%) of the original, which contributes to the best reproduction of the relief of forms with complex configurations, for example, dental casts, jaws, face, etc. If necessary, gas waste can be regenerated by treating it with saturated steam in an autoclave or vulcanizer at 125-130° (which corresponds to a steam pressure of 1.2-1.5 am) for 4-5 hours.

Plaster can cause chronic conjunctivitis, runny nose, weakened sense of smell, nosebleeds, dullness of taste, redness of the pharynx, and chronic laryngitis. The maximum permissible concentration of gypsum dust in the air is 2 mg/m3. During industrial development of gypsum deposits and in the production of gypsum products, it is recommended to use respirators.

Gypsum, or calcium hydrogen sulfate, is a mineral widely used in construction, medicine and sculptural casting. When finished, it is a powder that is mixed with water, after which it gradually dries, acquiring high hardness. Its color can be white, gray or with shades of brown, pink, yellow or red. The hardness of the mineral on the Mohs scale is 2 points.

Gypsum mining

The mineral occurs as inclusions in sedimentary rocks. Its particles are presented in the form of scaly or fine-grained masses. Its deposits are usually found in clayey sedimentary rocks. Outwardly they resemble marble. The mineral is mined using the mining method. Underground deposits are broken off from the total mass by point explosions. The extracted gypsum stone is delivered to the surface and then ground into powder. Initially, it has high humidity, so it is first dried and subsequently baked for several hours. The gypsum coming out of the kiln is completely ready for use.

The technological process may include additional methods for purifying the composition from impurities, which depends on the raw materials used. If the production of gypsum for medical purposes is required, then it is purified more efficiently to improve its binding properties.

Advantages of gypsum as a material

Gypsum has a number of advantages that allow it to significantly surpass the vast majority of other materials used in construction, as well as other fields.

Its undeniable advantages include:

• Light weight.
• Easy mixing when preparing solutions.
• Fast hardening.
• Short drying period.
• Moderate hardness.

The undoubted advantages of gypsum include the possibility of its easy grinding. Thanks to this, you can correct the shape of the product made from it. Depending on the object or surface, this can be done or specially.

The listed properties, which are advantages of the material, may differ depending on the degree of grinding, cleaning and the presence of plasticizers. It is usually classified according to the degree of compression. According to this criterion, there are 12 types of gypsum. This indicator measures the number of kilograms per square centimeter that must be applied to destroy the material. The number in the nomenclature name indicates a given number of kilograms. For example, gypsum marked 5 has an upper compression point of 5 kg/cm².

Where is gypsum used?

There are 3 main areas of application of this material:

1. Medicine.
2. Sculpture.
3. Construction.

Medical use

Purified gypsum powder is used to create a bandage to lock the limbs, which is necessary for the healing of broken bones. To do this, it is diluted in water to prepare a liquid solution. Bandages are soaked in it, which is used to make a dressing. After hardening, the bandage-reinforced solution becomes rigid, completely protecting the plastered limb from unwanted effects.

For medical purposes, only fine grinding of gypsum is used, ensuring high solidity after setting. In addition to being used to treat fractures, it is also used in dentistry. With its help, impressions of teeth are made for the further production of implants. With the advent of more modern non-staining materials, this method is becoming a thing of the past.

Plaster in sculpture

The use of gypsum has found its application in artistic creativity, in particular the creation of sculptures. For this purpose, high-quality grinding without impurities is used, similar to that used in medicine. There are two ways to use it. The first involves cutting out works from large gypsum stones, and the second involves ordinary casting. Plaster carving is practically no longer used, since the resulting works have external defects, which is due to the heterogeneity of the natural material. In addition, this production method requires great skill and significant time investment. It is much easier to pour gypsum mortar into molds. It hardens quite quickly, thanks to which, having an injection mold, such production can be put on stream.

Gypsum products are far from eternal, because their hardness on the Mohs scale is only 2 points, which is of course less than concrete, which scores 4-5 points. It is destroyed by mechanical impact. Nevertheless, the advantages of gypsum include maintainability, because products made from it can be glued together, and the resulting seams can be easily sanded down with emery cloth. After sanding, defects can be completely hidden with sufficient skill.

Construction use

Most often, gypsum is used to create plasters. Unlike cement or lime compounds, they have a more convenient consistency for work. At an average temperature of +20°, the drying time for such plasters is only 7 days. During this time, they fully gain their strength, which is 4 times faster than in the case of concrete.

Putties are also made from gypsum. They use a finer grinding fraction than plasters, due to which the resulting surface is highly smooth. This is especially important if wallpapering, and even more so painting, is required.

Decorative products for finishing are poured from gypsum. It is made from:

• Wall 3D panels.
• Wall tiles.
• Lepnin.
• Baguettes.
• Columns.
• Pilasters.
• Moldings.
• Ornaments.
• Designer sockets.

The vast majority of gypsum produced for construction purposes is used to make drywall. It is used as a level base for the quick construction of interior partitions and suspended ceilings. Drywall is also used to level out large curvatures in walls.

Using plaster to create decorative elements

Gypsum powder is an excellent material for the production of interior decorations. Most often, 3D wall panels are made from it, as well as various products to imitate ancient architecture. With the advent of polyurethane, such interior items began to be made from it, but gypsum still remains an accessible material that is used if you want to make such decorations with your own hands. For this purpose, 3D molds made of plastic or silicone for casting are offered for sale at quite reasonable prices. When using them, pure gypsum compounds are used. Ideally, the sculptural variety is suitable, but its cost is too high, which is not economically viable. A better choice would be to use granular plaster, sold in stores under the name alabaster.

For production, alabaster is diluted with water in equal proportions. The resulting liquid composition is poured into the mold, after which it is shaken to ensure the release of air bubbles. It is best to install it on a vibrating machine. Its presence allows you to prepare a solution with less water added, which will subsequently have a positive effect on strength. The form is left until the alabaster sets. Usually in the summer, 25-30 minutes are enough for this. After removing the product from it, it is set to dry, and the mold can be reused the required number of times.

Since the mold depth is usually about 20-25 mm, at an air temperature of +20°, complete drying of the casting takes about 3 days. After this, the product can be used for its intended purpose.

When using molds, they must be lubricated to ensure proper casting yield. This can be done with technical petroleum jelly, but the easiest and cheapest way is to use ordinary refined sunflower oil.

Features of working with gypsum plasters

Gypsum-based plasters can be used for application to mineral surfaces. First of all, they are suitable for covering walls made of brick, concrete, aerated concrete, expanded clay concrete, etc. They are also used to level ceilings.

Although gypsum-based plasters and putties have good adhesion, surface preparation with the application of a deep penetration primer is required. This allows you to create an impermeable film between the base and the plaster, preventing the transfer of moisture to the wall or ceiling. This ensures that during the drying period the plaster will have enough water for the normal course of the chemical crystallization reaction between the mixed grinding of gypsum. In the future, this will ensure higher hardness of the material and resistance to mechanical damage.

Typically, gypsum plaster can be applied to a surface with a layer thickness of 0.5 to 3 cm. Some manufacturers offer gypsum mixtures with the addition of special plasticizers and other impurities, making plastering with a large layer thickness quite possible.

Gypsum-based plaster is characterized by less pronounced sliding of the material. Thanks to this, they require less trimming of the burrs. All this contributes to higher labor productivity when using them.

Gypsum is an easily absorbent material, which is why plasters and putties based on it are unsuitable for use in bathrooms. In conditions of high humidity, the possibility of layer destruction increases many times over. To solve this problem, special moisture-proof polymer compositions are produced, but even with their use, cement plasters are still more reliable.

97. Plaster and plaster casts. Plaster bandages, splints. Basic types and rules for applying plaster casts.

Plaster casts are widely used in traumatology and orthopedics and are used to hold fragments of bones and joints in their given position.

Medical gypsum is a semi-aqueous calcium sulfate salt, available in powder form. When combined with water, the hardening process of the gypsum begins after 5–7 minutes and ends after 10–15 minutes. The plaster gains full strength after the entire bandage has dried.

Using various additives you can speed up or, conversely, slow down the hardening process of gypsum. If the plaster does not harden well, it must be soaked in warm water (35–40 °C). You can add aluminum alum to the water at the rate of 5–10 g per 1 liter or table salt (1 tablespoon per 1 liter). A 3% starch solution and glycerin delay the setting of gypsum.

Since gypsum is very hygroscopic, it is stored in a dry, warm place.

Plaster bandages are made from ordinary gauze. To do this, the bandage is gradually unwound and a thin layer of gypsum powder is applied to it, after which the bandage is again loosely rolled into a roll.

Ready-made non-shedding plaster bandages are very convenient for use. The plaster cast is intended to perform the following manipulations: pain relief for fractures, manual reposition of bone fragments and reposition using traction devices, application of adhesive traction, plaster and adhesive dressings. In some cases, it is permissible to apply skeletal traction.

Plaster bandages are immersed in cold or slightly warmed water, and air bubbles that are released when the bandages get wet are clearly visible. At this point, you should not press on the bandages, as part of the bandage may not be saturated with water. After 2–3 minutes, the bandages are ready for use. They are taken out, lightly wrung out and rolled out on a plaster table, or the damaged part of the patient’s body is directly bandaged. To make the bandage strong enough, you need at least 5 layers of bandage. When applying large plaster casts, you should not soak all the bandages at once, otherwise the nurse will not have time to use some of the bandages within 10 minutes, they will harden and will be unsuitable for further use.

Rules for applying bandages:

– before rolling out the plaster, measure the length of the applied bandage along the healthy limb;

– in most cases, the bandage is applied with the patient lying down. The part of the body on which the bandage is applied is raised above the table level using various devices;

– the plaster cast should prevent the formation of stiffness in the joints in a functionally unfavorable (vicious) position. To do this, the foot is placed at a right angle to the axis of the shin, the shin is in a position of slight flexion (165°) at the knee joint, the thigh is in a position of extension in the hip joint. Even with the formation of contracture in the joints, the lower limb in this case will be supporting, and the patient will be able to walk. On the upper limb, the fingers are placed in a position of slight palmar flexion with the first finger opposed, the hand is in a position of dorsal extension at an angle of 45° in the wrist joint, the flexor forearm is at an angle of 90-100° in the elbow joint, the shoulder is abducted from the body at an angle of 15– 20° using a cotton-gauze roll placed in the armpit. For some diseases and injuries, as directed by a traumatologist, a bandage may be applied in the so-called vicious position for a period of no more than one and a half to two months. After 3–4 weeks, when initial consolidation of the fragments appears, the bandage is removed, the limb is placed in the correct position and fixed with a plaster;

– plaster bandages should lie evenly, without folds or kinks. Anyone who does not know desmurgy techniques should not apply plaster casts;

– areas subject to the greatest load are additionally strengthened (joint area, sole of the foot, etc.);

– the peripheral part of the limb (toes, hands) is left open and accessible for observation in order to notice the symptoms of compression of the limb in time and cut the bandage;

– before the plaster hardens, the bandage must be well modeled. By stroking the bandage, the body part is shaped. The bandage must be an exact cast of this part of the body with all its protrusions and depressions;

– after applying the bandage, it is marked, i.e., the diagram of the fracture, the date of the fracture, the date of application of the bandage, the date of removal of the bandage, and the name of the doctor are applied to it.

Methods of applying plaster casts. According to the method of application, plaster casts are divided into lined and unlined. With padding, a limb or other part of the body is first wrapped in a thin layer of cotton wool, then plaster bandages are placed on top of the cotton wool. Unlined dressings are applied directly to the skin. Pre-bone protrusions (area of ​​the ankles, femoral condyles, iliac spines, etc.) are isolated with a thin layer of cotton wool. The first bandages do not compress the limb and do not cause bedsores from the plaster, but do not fix bone fragments firmly enough, so when they are applied, secondary displacement of the fragments often occurs. Unlined bandages, if not carefully observed, can cause compression of the limb, leading to necrosis and pressure sores on the skin.

According to their structure, plaster casts are divided into longitudinal and circular. A circular plaster cast covers the damaged part of the body on all sides, while a splint cast covers only one part. A variety of circular dressings are fenestrated and bridge-like dressings. A windowed bandage is a circular bandage in which a window is cut out over a wound, fistula, drainage, etc. Care must be taken that the edges of the plaster in the area of ​​the window do not cut into the skin, otherwise the soft tissues will swell when walking, which will worsen the wound healing conditions. Protrusion of soft tissues can be prevented by covering the window with a plaster flap each time after dressing.

A bridge bandage is indicated in cases where the wound is located throughout the entire circumference of the limb. First, circular bandages are applied proximally and distally to the wound, then both bandages are connected to each other with U-shaped curved metal stirrups. When connected only with plaster bandages, the bridge is fragile and breaks due to the weight of the peripheral part of the bandage.

Bandages applied to various parts of the body have their own names, for example, corset-coxite bandage, “boot”, etc. A bandage that fixes only one joint is called a splint. All other bandages must ensure immobility of at least 2 adjacent joints, and the hip bandage – three.

A plaster cast on the forearm is most often applied to fractures of the radius in a typical location. The bandages are laid out evenly along the entire length of the forearm from the elbow joint to the base of the fingers. A plaster splint for the ankle joint is indicated for fractures of the lateral malleolus without displacement of the fragment and ruptures of the ankle joint ligaments. Plaster bandages are rolled out with gradual expansion at the top of the bandage. The length of the patient’s foot is measured and, accordingly, 2 cuts are made on the splint in the transverse direction at the bend of the bandage. The splint is modeled and strengthened with a soft bandage. Splints are very easy to turn into circular bandages. To do this, it is enough to strengthen them on the limb not with gauze, but with 4–5 layers of plaster bandage.

A lining circular plaster cast is applied after orthopedic operations and in cases where bone fragments are welded together by callus and cannot move. First, the limb is wrapped in a thin layer of cotton wool, for which they take gray cotton wool rolled into a roll. It is impossible to cover it with separate pieces of cotton wool of different thicknesses, since the cotton wool will become matted and the bandage will cause a lot of inconvenience to the patient when wearing it. After this, a circular bandage in 5–6 layers is applied over the cotton wool with plaster bandages.

Removing the plaster cast. The bandage is removed using plaster scissors, a file, plaster forceps and a metal spatula. If the bandage is loose, you can immediately use plaster scissors to remove it. In other cases, you must first insert a spatula under the bandage in order to protect the skin from cuts from the scissors. The bandages are cut on the side where there is more soft tissue. For example, a circular bandage up to the middle third of the thigh - along the posterior outer surface, a corset - on the back, etc. To remove the splint, it is enough to cut the soft bandage.