The Impression Trays are of 2 main types:
1) Dentulous: These are trays which are used to take impressions of people with teeth or of a dentulous mouth.
2) Edentulous: These are trays which are used to take impressions in an edentulous mouth or a patient without teeth.
The are again divided into two types, based on the presence of perforations in it:
1) Perforated: There are small perforations or holes in the tray.
2) Non-Perforated: There are no perforations in the trays as they are used to carry impression materials which are not rigid Ex. Alginate.