Depending on the impression material used and the purpose of the impression, a certain type of confection spoon (factory scoop) is selected for the entire dental arch or part thereof:
- Metal perforated impression tray (with numerous small holes in the entire spoon);
- Metal non-perforated impression tray, with or without water cooling;
- Plastic disposable printing spoon with perforations;
- (Disposable) "Borderlock" spoons, distal with a raised edge with "rimlock".
All types are available in various sizes, usually standard in four or five sizes, suitable for adult teeth. A small print size is usually required for printing a denture. It is also possible to use a partial front scoop for this (see image below).
An even thickness of the print material gives the best results. The fit of the impression spoon must therefore be well adjusted to the number of teeth that are still present in the jaw. For example, there are separate spoons for fully toothed jaws, spoons for partially toothed jaws (to be used for immediate prostheses) and separate spoons for unpaid (edentate) jaws.
Because an optimal fit of the impression spoon can achieve the optimum quality of the impression, some manufacturers have developed sets for different jaw shapes. For example, there are sets for elongated V-shaped jaws, but also for wide U-shaped jaws. With such sets of ready-to-wear spoons, the individual shape variation can be taken into account; this certainly improves the quality of the print.
Individual plastic spoon
It is also possible to use a printing spoon that is specially made for a specific patient. This type is called the individual spoon and is made on a so-called initial model. The print for that initial model is of course made with the help of a ready-made spoon. For working with an individual spoon, an additional session is therefore sometimes necessary because an initial print must first be made.
These spoons have the best fit and therefore give the most reliable representation of the situation in the mouth. They are used for precision workpieces such as crown and bridge work and (frame) prostheses. Depending on the media to be used, they can be perforated or not. Graduate dental assistants generally have the ability to make individual impression trays. However, in order to save time, a dental laboratory is asked to make the individual spoons.
Unperforated impression trays must have a rimlock for the retention (hold) of the impression material. A rimlock is a bulge on the inside of the spoon edge where the material remains behind when the print is taken out.