This method (system Model-tray; Nu-logic Tray-model; Let-Lok) is easy to handle as it does not require the use of special drills for drilling and special glue. Additionally, this method saves supergips and time for its preparation.
A set of tools for this method includes:
- partial and full plastic caps (E-Z tracolle) reusable;
- disposable plastic retention guides for extracting models of a polymer base;
- the device, which is a small press to extract models of the dentition of the polymer of the cap.
Creating collapsible models by this method consists of the following main stages:
1) preparation of print (the edges of the print are cut so that it fits close to the base polymer of the cap);
2) preparation of polymer cap with retention guides. After spray coating the insulating layer on the inner surface of the polymeric base and retention guides, the latter are mounted in the base. The application of such isolation is necessary for free extract retention guide rails with portions of the model of the dentition from the base;
3) receiving model: supervisor consistently fill the mold and the cap on the vibrating table, after which the print is installed in the base;
4) separation of the impression from the model, which is carried out after the crystallization of gypsum;
5) retrieve the model from the base with a special press (the retention guides are freely out of the cap);
6) remove excess plaster carbide cutter and a cutting of the model into fragments using a jigsaw or by using a diamond disk;
7) installation of portions of the model after processing to its place for further modeling frameworks-cast bridge dentures.
Advantages of getting portable models by this method are:
- no need to use additional devices for obtaining models;
- the existence of universal bases that are used for both the upper and lower jaws. When this plastic base protects the model from the linear expansion that occurs when sawing gypsum;
- no need to mark the future location of the cut pattern;
- sawing model of the dentition allows each portion of the model to take its place without effort, as the numbering on the inner surface of the cap serves as a reference for quick setting of the fragment to its place;
- time consumption for obtaining the model do not exceed 10 minutes (excluding the time of hardening of gypsum);
- using a minimum amount of super plasters.
The disadvantages of this method include the fragility reusable caps when fixing plastic retention guides. In addition, the process of cutting the model is rather labour-intensive: when using diamond saw blade is overheating (melting) the plastic retention guide; when using a jigsaw it is very difficult to make a smooth cut due to the presence of two different structure of materials (plaster and resin).