In the article, we will consider what are the impression masses for casts.
The quality of the material, as well as the competence of the dentist to whom a person comes for treatment, is a very important factor in the process of making casts or impressions of the dentition. A cast or impression is a negative image of the jaw in a convex form. In other words, this is a display of the teeth necessary to create a prosthesis, as well as other jaw areas.
Purpose and use in dentistry
The most popular field of application for impression materials is dental prosthetics. Impression specialists are orthopedists and orthodontists. The terms cast and impression are usually used interchangeably. But someone thinks that under them are products that are made of various materials.
Impression materials are used for certainindications depending on the state of human he alth, the characteristics of the pathological condition of the soft tissues of the oral cavity and dentition, the design of the manufactured prosthesis or apparatus.
Types and description of impressions
The available impression or impression materials in orthopedic dentistry are divided into two large groups: elastic and hard. The latter are converted chemically (irreversible), as well as thermally (reversible). In the following, some types of impression materials in dentistry will be discussed in detail.
Gypsum
Gypsum is an irreversible raw material - it is produced by roasting natural gypsum. The sieved raw material is mixed with water before making an impression and the plaster quickly hardens, which makes it possible to create clear impressions. This material has the following disadvantages: poor grinding - low quality - does not allow the mixture to harden quickly; high probability of breakage due to fragility; not all substances can be used when detaching the impression and model (for example, those containing fat). It is very important to follow the rules for storing it in a dry room. When stored for a long time, lumps begin to form in the gypsum powder.
Dignity of gypsum:
- affordable price;
- no unpleasant taste and smell;
- obtaining an accurate drawing;
- non-stickiness;
- no negative impact on the oral mucosa and tissues around the teeth.
Zinc oxide eugenol pastes
Zinc oxide eugenol pastes are another irreversible material. Water and zinc eugenolate are mixed in them, and the mixture after such a reaction acquires plasticity. Dentists use them for adentia (partial or complete), that is, the absence of teeth. Such a mixture can be preferred because it is easily separated from the model, adheres quickly and has high definition. However, it is very important to knead it correctly, as the pastes can break during removal due to their fragility.
What other impression materials are there?
Thermoplastic masses
Reversible solids include thermoplastic masses: stearin, rosin, paraffin, gutta-percha, stens, wax, Kerr mass, Weinstein mass. These materials have the distinctive property that they become plastic when heated.
In this case, the softening of these substances should be carried out at a temperature of no more than 60 degrees Celsius, otherwise you can burn the oral cavity. Properly heated mass for taking impressions is perfectly corrected during processing, however, the temperature of the human body is optimal. Another essential property is homogeneity. In addition, a good mass of this type will not become sticky and will be safe for he alth at high temperatures.
Alginate impression material
Alginic acid sodium s alt, or alginate, is a water-miscible powder. To get the right mixture, you need to clearlyadhere to the proportions of water and powder. Alginate has several disadvantages: a large amount of water will cause slow hardening; poorly mixed mass will crumble. It is also important to strictly observe the mixing ratio, for which it is better to use packaged powder bags to get an impression. With the right actions during the mixing process, the cast is obtained quickly and easily, it is well separated from the model, keeping the resulting shape for a long time.
Is there a silicone impression mass?
Impression elastomeric materials
Impression elastomeric substances in the field of dentistry are divided into thiokol, polyester and silicone. There are two types of silicone impression materials: additive and polycondensation.
These materials are based on a base paste that reacts with a catalyst, solidification occurs in three to four minutes. An additional layer is applied on top to get all the protrusions, recesses and contours. Such raw materials are good to use for creating an initial impression, a touch-up composition or a custom tray. Like other substances, it has a number of advantages: moderate cost; high accuracy; accelerated adhesion, that is, the adhesion of bodies of various kinds; lack of taste and smell. However, there are also disadvantages: it will take two hours to make a model; the mixture is able to absorb moisture and becomes in this case of poor quality; the model may shrink; the product is capable of changing its shape under pressure.
Thisconfirms the instructions for the impression material.
Polyester masses
Polyester masses are understood as pastes with an average consistency. They are based on polyesters with a low molecular weight. Then the impression mass is filled with silica, glycol etherphthalate gives it elasticity. Then it is packaged in tubes (or tubes).
Benefits of mass data:
- versatility – wide scope of use in orthopedics;
- secondary application when creating a model;
- high print accuracy; fast curing;
- long service life - its density lasts longer than a month;
- sufficient strength;
- impression can be sterilized.
However, in this case, there are also disadvantages: the difficulty of extracting from the patient's oral cavity and the high cost of the substance.
Instructions for taking impressions
The doctor first examines the oral cavity, if necessary, treats or removes individual teeth. When the patient has chosen a design, further preparations are underway for taking an impression. The specialist injects an anesthetic solution and prepares the bony organs of the oral cavity for imprinting. Then he dries his mouth with cotton swabs. After that, the doctor needs to knead the material from which the cast will be made. The cast can be taken in different ways. One of them consists in the following actions: an adhesive is spread on a spoon, then a dense paste, an impression of the teeth is immediately taken.
This is all done before preparationelements so that there is room for a corrective composition. After the preparation of the teeth in the recesses of the supporting gingival elements, expansion occurs. It is there that you need to insert retraction threads that are impregnated with the composition of the vasoconstrictor. To stop bleeding from the gums and fix the threads, a cotton cylinder is placed in the prepared element. At the end, the patient closes his mouth so that the recesses between the gums and teeth do not bleed. The doctor removes the paste of this impression and fills it with a new composition. After that, the impression is sent a second time to the oral cavity and is now completely dry.
Top Mass Rankings and New Items
Currently in Russia, in more advanced clinics, the following dental impression masses are most often used: alginate, polyester and silicone. They are considered the best in the field. It should be noted that there is no universal composition for creating dental impressions, which would be highly accurate, suitable for doctors in any case and would not have drawbacks. It is also known that a new method is currently being introduced - scanning a number of teeth and creating their models from 3D images. Perhaps this will lead in the future to a partial disappearance in the dental field of casts using impression materials.
