Today, dentists are armed with a huge number of tools for various purposes. In addition, the first impression materials appeared many years ago. But there was not much variety in their choice.
Fortunately, today there are a large number of them, so experienced doctors can choose one or another material at their discretion. Often this leads to the fact that some specialists, especially beginners, make mistakes and choose incorrectly what is better to use for making an impression. This leads to poor quality results. Therefore, it will be useful to understand the classification of impression materials, as well as what advantages and disadvantages each of them has.
What is an imprint
In simple terms, we can say that this is a cast, which is a reverse display of the surface of a hard or soft tissue located on the prosthetic bed. Thanks to these impressions, it is possible to develop the most optimal prostheses, even for those clients who have lost most of theirteeth.
It all depends on the quality of the impression material: whether it will be comfortable to wear the finished structure or, on the contrary, it will not correspond to the physiological characteristics of the patient at all. Therefore, when choosing such compounds, special attention should be paid.
Alginate masses
In this case, we are talking about a powder that is diluted with water and forms a rather soft and viscous mass that hardens within 2-3 minutes. If we talk about the advantages of this material, then first of all it is worth noting its low cost and ease of use. When using alginate mass, a high-quality impression is obtained for the future prosthesis. At the same time, the finished model is very easily removed from the spoon.
However, when considering dental impression materials, you should pay attention to the fact that the alginate mass does not allow you to make a model that will meet the individual characteristics of the patient. This is primarily due to the fact that 2-3 minutes is not always enough for the quality of the necessary work, if we are talking about a difficult case. The material shrinks too quickly. This leads to the fact that the specialist is required in a matter of seconds to have time to make a good model that will meet all the requirements. Although the material is well removed, at the same time it does not adhere well to the spoon.
Features of alginate masses
Impression materials of this type can be found in the free sale in almost any pharmacy. However, you need to choose the product that additionallyequipped with a measuring cup. The fact is that in this case it is not recommended to add water "by eye".
If the amount of liquid is too small, then the finished mass will be with increased viscosity. This means that the material was produced in violation of technology. In this case, this will lead to an increase in shrinkage. If, on the contrary, there is too much water, then the finished mass will turn out to be very liquid. It will begin to spread over the spoon, and the print will turn out to be of insufficient quality. This is a serious disadvantage.
To deal with poor material adhesion, it is recommended to use perforated type spoons.
Silicone
In this case, we are talking about impression materials that are very popular with dentists. Such compositions may differ depending on the type of vulcanization of the material. Each of them has its own characteristics.
If we talk about the classification of impression materials of this type, then there are C-silicones and A-silicones. In the first case, the prefix means condensation, in the second - addition. As a rule, on sale they are marked in this way. However, if the exact type of silicone is not indicated on the label, then you can determine it yourself. To do this, it is worth evaluating the appearance of the product.
C-silicones are always sold in a large jar, which contains the mass, and in addition to it, a small tube of hardener is included in the package. In some situations, additional material is added in the form of a catalyst. If we are talking about A-silicones, then in this case the product is sold in the form of twojars of exactly the same size. They contain masses of different colors.
Silicones are classified as agar impression materials. This means that they must have good stickiness.
C-silicone
If we talk about the features of these impression materials, then they also need to be mixed in a clear proportion. When too much catalyst is added to type C silicone, a polymer-type network forms. Often an additional component is added in large volumes in order to speed up the process. This really helps, but in this situation, the assistant may have difficulties, since he simply does not have enough time to mix the ingredients.
If you use less catalyst, then in this case you can notice a slowdown in the solidification process. This is justified if the doctor needs to take an impression immediately from a large number of surfaces. However, one must be prepared that in this case the polymerization process will be disrupted. This will negatively affect how elastic and elastic the mass will be.
Impression materials of this type have their own advantages. Among them, one can note low cost, good manufacturing accuracy of the final structure, low shrinkage, good elasticity with sufficient strength. In addition, the material is well exposed to disinfection procedures. But this type of silicone also has a lot of disadvantages.
For example, mixing components can only be connected manuallymode. The use of special equipment is prohibited. This leads to the fact that the first time it is not possible to achieve a uniform consistency when mixing the catalyst and the base. Also, the disadvantages include the fact that even a slight departure from strict proportions can lead to the fact that the finished mass will be of poor quality. In addition, C-silicones are highly sensitive to moisture. They absorb water well, which is also a minus. Among other things, such impression materials do not adhere well to the tray. And if you turn to official literary sources, you can find a huge amount of information that silicone is a toxic material.
When using them, you should pay attention to several important points. For example, when working with such material, it is always recommended to use a special syringe. Both plastic and metal models are suitable for this. It is also worth noting that C-silicones are considered quite safe today. However, in some situations, cases were recorded that this material caused the growth of staphylococci on mucous surfaces. Therefore, after applying such a material, it is recommended that the patient rinse the mouth abundantly. In addition, in the process of mixing the mass, the specialist must wear gloves. If a drop of the composition got on the clothes, then you should not immediately wash it, it is better to wait until the material has completely solidified.
A-silicone
If we talk about this group of impression materials in dentistry, then it is worth paying attentionattention to the fact that they differ in a rather specific reaction during the polymerization process. It lies in the fact that, as such, by-products are not formed. Therefore, these materials are considered among the most stable.
If we talk about their advantages, it is worth highlighting a very good reproduction of the required designs. In this case, the mass and the catalyst are mixed very well and quickly turn into a homogeneous mixture. In this case, the model can be stored up to one month after the impression was made.
Also silicone impression materials of this group are very resistant to deformation and recover well in case of damage. Upon receipt of one print, you can make several models at once. In addition, the material is more resistant to moisture and good adhesion. The use of disinfectants is allowed. Also, special devices can be used to mix the composition, so manual labor is not required, which greatly simplifies the work of dental laboratory staff.
The main advantage of such materials is that they do not adversely affect the mucous membrane.
Of the minuses, experts single out only the relatively high cost of this product.
Features of A-silicone
These elastic impression materials are suitable for those who prefer the use of retraction cords. In this case, we are talking about a fairly strong, but fluid material. Silicones of this group are characterized by increased hydrophilicity,therefore, prints are of high quality even if they get saliva, blood or any other type of liquid. In this case, they outperform C-silicones to a greater extent.
It is noteworthy that the hydrophilic properties are retained in the cast even after the polymerization process is completed. In addition, materials of this type come in different viscosities. This makes it possible to obtain impressions of all kinds using any manufacturing technique. Doctors also note that the base itself and the catalysts have a homogeneous consistency, so they mix perfectly. Since both components differ in color, it is very easy to determine when the kneading process can be completed.
Thermoplastic impression materials: properties and features
The main feature of the components of this group is the ability to harden or soften depending on temperature. When heated, such materials become more fluid, and when abruptly cooled, they harden almost instantly. Their main advantage is that they are made from resins of a natural or synthetic type. Additionally, they may contain modifiers, plasticizers and dyes. This improves their adhesion properties and other parameters.
Also, paraffin, beeswax and other substances can act as a thermoplastic component. However, it is important to ensure that when heated, the mixture cannot damage the patient's mucosa. Also, when buying a material, you need to make sure that it does not soften from temperature.the patient's body or, conversely, will not harden too quickly.
Using plaster as an impression material
This component has long been used in dentistry. Therefore, during this time, many of its varieties have appeared. There is even GOST, according to which there are five classes of dental plaster. Consider them in more detail:
Plaster for impression. In this case, we are talking about the material that is used to make casts. In this case, it is possible to make both partial and whole impressions of the entire jaw, in which there are no teeth at all. This type of gypsum is characterized by rapid setting and less expansion
- Medical. In this case, we are talking about alabaster gypsum, which does not have accelerated hardening. As a rule, such materials are used for the manufacture of anatomical models for subsequent diagnostics. This cast is not strong enough for other procedures.
- High strength for models. This is a harder material that is suitable for making removable dentures. Unlike the previous type, it has a high strength class and improved characteristics.
- Super-strong plaster for models. This material also features a very low expansion rate and excellent strength. As a rule, it is used in the manufacture of high-end collapsible models.
- Super-strong gypsum with adjustable expansion capability. It is not easy to meet such material, as it is very expensive and is considered one of the mostupscale. It is used for high accuracy models.
If we talk about the features of impression plaster, then it is worth highlighting a fairly simple mixing process. However, in the process of connecting the components, air must not be captured so that air pores do not appear inside the material. This may cause defects.
In all other respects, ready-made gypsum does not bring great difficulties to the dental laboratory staff. The mixture has a low viscosity, does not absorb moisture, spreads well over soft tissues and does not injure the mucous membrane. At the same time, plaster allows you to reproduce the smallest details.
When working with this material, it is recommended to use an individual spoon. It is best if it is made of acrylic plastic. Plaster impressions are also taken using this material in the form of a fluid mixture. In this case, the spoon must be made of thermoplastic material. The finished print is well stored and does not deform for a long time.
Polyesters
In fact, these materials were known back in the 60s of the twentieth century. However, for a long time they were not very popular. Nevertheless, many years later, they were still noticed, and experts began to actively use them.
If we talk about the advantages and disadvantages of this material, then among the advantages, first of all, it is worth highlighting the fact that polyesters can be used in almost any job. This material is characterized by high precision, ease of mixing. At the same time, it is possibleuse an automatic device. In addition, polyester is resistant to moisture. One print can be used to prepare several models at once. The setting time of the material is quite short, so the work is carried out quickly. The finished model is solid. Impressions can be sterilized and soaked in absolutely any solution that is used as a degreaser. The finished cast does not deform for 3 weeks after production.
If we talk about the disadvantages of this material, then some experts pay attention to the fact that the finished impression can be very difficult to remove from the patient's mouth. In addition, polyester is much more expensive than silicone counterparts.
Features of polyester
If we talk about the mass itself, then it is one component. In addition, it is worth noting that polyester is considered a very stable material. In the absence of pressure, it is absolutely unchanged, however, if only pressure is applied to it, then it can become much softer. On a spoon, the finished mixed mass will not spread. Instead, it will lie in a very dense slide. However, the moment the spoon begins to put pressure on the teeth, the mass immediately becomes very soft. It will create an optimal impression. Due to this, serious damage to the mucous membrane is not applied. This means that the specialist will not need to press hard on the material in order to get the most accurate model.
In closing
Having considered comparativecharacteristics of impression materials, it is much easier to make a choice. For example, if you prefer silicones, then it is better to choose a material of category A. If you buy gypsum, you need to make sure that it is of the right class and is suitable for the planned work. When working with thermoplastic materials, care must be taken that they do not become very hot before contact with the mucosa.
In no case should the composition be toxic. It must be understood that even with a short interaction with the mucous membrane, this can cause a severe allergic reaction and cause serious harm to the patient's he alth. Therefore, it is best to give preference to high-quality and proven materials. They are much better stored, mixed into a homogeneous mass and allow you to make high-precision casts.
