In dentistry, a distinction is made between elastic and rigid impression materials. The rigid material gypsum z. B. is used to more accurately determine the position of the teeth, elastic impression materials in turn serve the actual production of the tooth models, are made of natural or synthetic polymers in which a solidification by chemical or physical conditions is achieved.
In order to make an impression, the dentist needs material that has a soft surface so that the area to be examined and used for the impression can leave the exact and detailed shape through contact. After the patient has bitten on the impression material, it must be easy to separate from the teeth and at the same time preserve the shape, so they are not destroyed during the weight loss. Serve various materials that are duro- or thermoplastic or consist of a solidified liquid.
After removing the impression from the mouth, the finished impression is cleaned under running water of all saliva residues and examined more closely for the possible implementation and usability of a modeling. All rows of teeth as well as the necessary toothless sections of the jaw must be completely visible and exactly marked by the impression. If, for example, air bubbles are present, they become gypsum pearls in the finished model and prevent the exact assignment of the impression model.
The tooth and jaw impression must therefore be accurate to the drawing and must have no change in the surface shape. Therefore, dentistry uses various impression materials that meet these conditions. Such are gypsum, wax, alginate, silicone, hydrocolloid and polyether.
It is important that impression materials have good flowability and tolerate moisture to maintain the desired accuracy of the boundaries of all tooth structures. Only then can a denture be made later from the impression, which fits exactly in the mouth area.
Furthermore, the material must be able to cure quickly after the impression, while at the same time enough time must be left to process the material. Each impression is poured out after removal and solidification with gypsum. The dental technician creates the prosthesis or denture from the plaster model.
One of the much used materials is alginate. It belongs to the elastically natural materials, consists of seaweed and seaweed and allows an elastic-irreversible impression. Alginate is mixed with water to form a paste that turns into an elastic gel. Physiologically, the material is harmless and its structure allows high accuracy and the desired detail.
Alginate solutions are also used in model making to separate substances and prevent them from mixing or bonding. The model of plaster is then coated with the insulation of alginate and certain forms created with acrylic, which can be easily solved by the plaster model. However, the alginate impression must be poured out quickly with gypsum because the material alters the volume due to moisture loss.
Hydrocolloids in turn form colloids in combination with water and are therefore malleable. These too have alginate as a base. The gel material is heated and thereby viscous. While the impression is taken with hydrocolloid, it transforms back into a weakly elastic state, as the impression tray is cooled with water. The detail is true as with other impression materials, however, the model must be poured out immediately with gypsum, since hydrocolloid is not storable and has a high moisture loss. If the impression is not made fast enough, it can be mixed with the plaster and the appearance of the oral cavity is distorted. On the other hand, impression compounds of hydrocolloid, in contrast to alginate mixtures, are reusable. The gel is returned to its liquid state in a water bath.
Important synthetic materials include polyethers and silicones, which chemically fulfill their purpose in dentistry. Silicones are distinguished in A-Sillikone and K-Sillikone, ie in addition- and condensation-curing silicone impression compounds. They are used both for the impression of prepared teeth as well as for the representation of the mucosal areas and can be well disinfected. Polyether materials in turn have hydrophilic material properties and can reproduce tooth position well, especially in very watery mouths.
Most impression materials consist of two different components that are mixed and hardened immediately after processing. Some dental practices mix the material by itself, maintaining the exact concentration so that the impression is not distorted. The result would be a leaky or incorrectly fitting dentures.
Generally, impression materials allow the restoration of a strong dentition. Tooth decay, artificial crowns, bridges and braces can be tailored to fit, so that the patient can get both the chewing force and the dental aesthetics. Tags: