PRIMARY IMPRESSIONS
Usually taken in alginate in a stock tray. Used for treatment planning, designing of the denture and the construction of special trays. Size of tray is selected so that the teeth sit centrally within the trough of the tray. The impression should extend to the intended borders of the special tray.
MASTER IMPRESSIONS
Taken after the denture has been designed and any tooth preparation has been completed. Usually taken in alginate (or silicone if severe undercuts are present). The special trays are tried in and the extensions checked and modified if necessary. Fix is applied to the tray and the impression is taken. An accurate impression is required, with no imperfections (eg airblows) and adequate exstension. The dentures are then constructed on the casts produced from these impressions. There are a number of special impression techniques used in the construction of partial dentures, the following are covered in this program.
