This method includes the following manipulations:
By physician assessment of the quality of the print.
A print is called a reverse (negative) display of solid surfaces and soft tissue, located on the prosthetic bed and its boundaries.
A print is considered suitable if accurately imprinted the relief of the prosthetic bed (including the transitional fold, the contours of the gingival margin, interdental spaces, the tooth row) and on its surface there are no long delays, smazannost relief mucus.
The preparation of the print. The impression after rinsing under running room temperature water must be disinfected by one of the known methods. To relieve internal stresses in otlicnom material and improve the wettability (flowability plaster) surface of the imprint process (by dipping, applying with a brush or in aerosol form) with a special liquid to remove surface tension (e.g., Dick-CBE; Fixall, etc.).
Preparation of plaster. Mixing gypsum powder and water (based on 100 grams of powder from 22 to 24 ml of water) is carried out by:
- manual for it in the rubber Cup to advance noritomo the amount of water in small portions add the gypsum I – class III (ISO) and with a spatula mix it until smooth creamy consistency. While the more energetic will zameshivaetsya the mixture, the better will be the contact between the gypsum and water and, therefore, the faster the setting (the average setting time is about 7-10 min.);
- with the use of vacuum mixers, which usually operate in the automatic mode in a specified physician time interval. The liquid mixing extra hard gypsum (IV-V classes according to ISO), in addition to water, can be used a special liquid, which ensures a uniform distribution of the powder in liquid and the adhesion of the plaster. The tendency to the formation of pores on the surfaces of the gypsum in contact with water during the use of this fluid is reduced to a minimum. The resulting plaster model with different high homogeneous density, strength and fidelity of the original.
Mixed to the consistency of sour cream, plaster well fills the form and gives clear prints.
The filling of the impression involves making a batch of plaster with a spatula (manual option) or directly into the impression through the exhaust nozzle of a vacuum mixer (motorized or mechanical). To avoid porosity and cavities in the plaster model, filling the imprint with plaster accompanied by shaking and beating, but the most effective option is to use special devices — vibrostation . After filling in the marks of the teeth on the plaster with some excess place above the surface ofisnogo material and proceed to the formation of the cap model.
The design of the base to the plaster model is carried out in the following ways:
- with a spatula, for this gypsum mound superimposed on a smooth flat table surface, and turning over to him the impression is filled with plaster so that the height of the cap was 1.5-2.0 cm, and the bottom of the impression spoon was parallel to the surface of the table. The excess plaster around the perimeter of the impression and the impression spoon is removed with a spatula. The angle of the faces of the base of a plaster jaw model with the surface of the table is 90°;
- using a standard rubber core mold (koloty) for the base, in which, after pouring the plaster, placed filled with plaster impression;
- using elements of articulation bases supplied with most modern articulators.
The removal of the impression spoon and ofisnogo material with the jaw model carried out after the crystallization of gypsum. At the same time:
- in the case of elastic impression material — consistently, using tools (spatula, scalpel, tweezers, etc.), remove the tray and subsequently to the impression material, cutting it into fragments;
- in the case of using thermoplastic materials require preheating ofisnogo material with warm water. However, as a rule, the spoon is removed along with otecnam material.
The machining of the base to the plaster model of the jaw by cutting tools (plaster knife) and special equipment (edger), aimed at giving it a uniform thickness and parallel side faces by removing excess plaster.
In the world of dental practice, there are a number of methods (system Dowel-pin; Kiefer model; Cater; Model-tray; Nu-logic Tray-model; Let-Lok; Pindeks, etc.) create a collapsible plaster models, each of which has its own specific set of tools and equipment. The basic material for models in all systems is gypsum 3-rd and 4-th class (for ISO). In addition, such systems use plastic caps and pins (system Kiefer model and Cater), polymer caps without pins (system Model-tray; Nu-logic Tray-model; Let-Lok).
Thus, it is possible to allocate three basic ways to create collapsible plaster models of jaws:
- without pins, using polymeric base model;
- using pins and plastic cap model;
- with the use of pins and plaster base model.