The role of the tray:

 1. Frame: to support and restore the collapsed and deformed muscles due to dentition loss. Mucosa membrane.

 2. Container: no matter what impression material is selected, there must be a container to support and fix it, which is convenient for the operator to operate. 

3. Shaper: On the basis of the tray close to the physiological and anatomical morphology of the mouth, use the impression material to combine with the morphology of the oral mucosa to more accurately copy the structure and texture of the mucosa