In some dental treatments, there is a need to take an exact replica of your upper and lower teeth — especially in orthodontic treatment and making of dentures. Impression materials will be placed on metal/plastic impression trays. These trays will be inserted in your mouth for a few seconds or a minute depending on the setting time of the choice of impression material of your Dentist. The dentist may take the impression of upper teeth first then the lower, or vice versa. Dental stone will then be poured into the mould and will be allowed to dry in a few minutes. Once dried these replicas are called Diagnostic Casts.