Without which it is impossible to manufacture dentures in the modern world? Yes, without high-quality prints (functional and anatomical, which we will analyze further). To produce a suitable design, the imprint of the tissues of the upcoming prosthetic bed is necessary. Mastering the techniques of obtaining high-quality prints is a necessary stage in the career of each orthodontist. We will analyze the main classifications of these casts, methods for their preparation, as well as the materials that are used for their manufacture.
What is it?
What are anatomical and functional prints 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, alveolar bone, transitional folds of the mucous membranes, etc. The print is obtained using special materials.
The history in dentistry of anatomical and functional impressions began back in 1756! Then the German doctor Pfaff was the first to make a similar imprint, using plain wax as an impression material.
Why are prints needed?
Why do you need a print in orthodontics? It is on it that a positive model is made, which is an exact copy of hard and soft tissues of the oral cavity.
Various prints are used for diagnostic, therapeutic, educational, control and work purposes. Some models are valuable in that they help clarify or refute the patient’s diagnosis. Some are needed to make the prosthesis. And some make it possible to evaluate the effectiveness of the orthopedic therapy (cast before and after).
The so-called working functional impressions are needed for the further manufacture by prosthetic specialists. Assistants help to study the "relationship" of antagonist dentitions.
Gavrilov classification
The fundamental gradation in orthodontics is the division into functional and anatomical prints. What is the difference? The former are created taking into account the functional compliance, mobility of the matter that covers the prosthetic bed. The second, respectively, without such an account.
Consider the classification of prints:
- Functional. Most often they are removed from the toothless jaw. Less often - with the one where some teeth were preserved. The most important purpose is the basis for the manufacture of prostheses for toothless patients. It is these prints that help determine the optimal ratio of 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 chewing 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 form the edges of the prints relative to the position of the moving tissues, which will be located on the border with the prosthesis.
- Anatomical Additionally divided into main and auxiliary. The first type is removed from the jaw, on which the prosthesis will be installed later. The second - from the jaw-antagonist (upper or lower), on which the prosthesis will not be. 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.
From the characteristics, an important difference is distinguished between these varieties. Obtaining functional impressions is important for making a complete denture on a toothless jaw. The anatomical is more likely to be useful with partial prostheses, bridge devices, and other smaller structures.
Another important difference between anatomical and functional prints. For the first, standard impression spoons are used. And for the second, these tools are made individually for each patient. To better understand how impressions are produced, functional and anatomical, let's figure out what is considered an impression tray.
Impression spoon - what is it?
Impression spoons are made in the factory from plastic or stainless steel. Their shape and volumes are determined by many factors at once:
- The jaw of the patient.
- Type, breadth of the dentition.
- Location of the defect.
- The height of the crowns of the remaining teeth.
- The expressiveness of the alveolar processes of the jaw.
Even standard impression trays are varied in shape and size. First of all, they are divided into those intended for the upper and lower jaw. The removal of functional impressions, as we said, is carried out by individual spoons.
Each of these tools has a body and handles. The body of the spoon will consist of alveolar concavity, an external rim, curvatures for the sky. For example, standard impression spoons have ten sizes for the upper jaw, nine for the lower.
The use of varieties of spoons
When working with elastic materials for impression use special spoons with holes. This is due to the fact that the base does not adhere well to the metal from which the standard spoon is made. Some experts come out of this situation using their own inventiveness: an adhesive plaster is glued to the inside of a conventional metal tool. The elastic base adheres better to its rough rough surface.
Also, medical ingenuity and amateur activity is the cutting of the handles of such spoons with special scissors for metal in case of their excessive length. 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.
So-called partial spoons are much less commonly used. Used for 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
A functional impression of an individual spoon is carried out for toothless jaws. Such tools are distinguished by the height of the sides, the expressiveness of the niche for the alveolar processes, and somewhat smaller sizes. The reason is that the print should provide the specialist with more accurate data on the prosthetic bed.
Why do you need individual spoons? As a rule, it is difficult to find two toothless jaws that are absolutely similar in external characteristics. For accurate fixation of the prosthesis, functional suction is necessary here, which is created by creating negative pressure. To do this, it is imperative that the surface of the prosthesis being manufactured matches the tissues of the prosthetic bed, which will come in contact with it. Without an accurate fit of the edges of the spoon to the borders of the valve region, this result is difficult to achieve.
How is an individual spoon made? To begin with, using a standard tool in the orthodontic clinic, a complete anatomical cast of the jaw is made. Then, in the laboratory, an individual model of plastic is made on its basis.
Oxman impression base classification
We figured out the impression spoons. The second important component is materials for a functional print. 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, dental paste, adhesive, masses of Kerr and Weinstein.
- Elastic masses. Stomalgin and algelast are included in this category.
- Polymerizing masses. Silicone impression bases, AKT-100, stykril.
Classification of the impression base according to Doinikov and Sinitsyn
Imagine another classification common in orthodontics that separates the materials used to remove the functional and anatomical casts of the jaws.
In the beginning, two groups stand out. The first is according to the physical state of the material:
- Elastic.
- Polymerizable.
- Thermoplastic.
- Hard crystalline.
The second gradation divides the materials into categories by chemical nature:
- Alginate.
- Gypsum.
- Silicone
- Zinc Oxidegenol.
- Epoxy
- Thiocolov.
Crystallizing Materials
We describe in more detail the substances that are most often used in orthodontics for removing anatomical and functional prints. It is important to highlight medical plaster. Its other name is semi-aquatic sulfate salt. It is obtained from ordinary natural gypsum, subjected to special heat treatment. As a result of this process, material from two-water is converted to semi-water.
The alpha modification of medical plaster is considered the most suitable for dentistry. It is obtained at elevated pressure and temperature in an autoclave. The substance is distinguished by its best strength and density.
Elastic materials
The basic raw materials here are 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 and so on are additionally introduced into the composition for removing impressions. Gypsum turns a soluble gel into an insoluble one. The remaining components allow the gelation process to go more smoothly.
Functional Impression Requirements
The requirements for the resulting model are rooted in the requirements for the materials used to make the mold:
- Softening at a temperature that does not injure the mucous membranes of the oral cavity.
- Easy input / output from the patient’s oral cavity.
- Rapid hardening at a temperature that does not injure the mucous membranes.
- The requirement, which is one of the main wishes of hypersensitive patients, is that the mixture should not have an unpleasant smell and taste.
- The material is supplied hygienic, not losing its basic properties necessary for work during the sterilization process.
- Mixtures for the manufacture of prints should be affordable - at cost, assortment, delivery options.
Production of high-quality impressions is a necessary condition for obtaining a perfectly fitting denture. Therefore, this direction in orthodontics paid considerable attention. Today, there are special technologies for taking casts, a wide range of materials and tools necessary for this work.