A kit (1) to make an individual impression tray for dental use comprising essentially a standard model (20) reproducing a dental arch (24), a semifinished product of thermoformable material, for example a plate member (30), and a container (10) for a heat exchange liquid. The first step that is carried out by the dentist (60) to obtain the individual impression tray (100) provides the insertion of the model (20) in the container (10). Then, next to dental arch of the model (20) a plate member (30) is arranged and hereafter a certain amount of a liquid is put (15), for example water, in the container (10) up to covering plate member (30). The liquid (15) is then heated by a source of thermal power, for example a microwave oven (40) stopping heating when the temperature of the liquid (15) achieves a value T* higher than the temperature for softening the thermoformable material of the plate member (30). At the temperature T*, plate member (30) of thermoformable material is in the plastic state and therefore collapses on the standard model (20) assuming substantially its shape, obtaining a thermoformed plate member (30') equipped with a recess (101) at the side facing the model (20) and a corresponding projection (102) at the opposite side.