Making Alginate Dental Impressions

            Palatograms and linguograms should always be accompanied by diagrams showing the shape of that particular speaker's mouth in the form of a traditional sagittal section.  Diagrams of this kind can be based on dental impressions of the oral cavity made in the field.  Use chromatic dental alginate (such as Jel-Trate) as the impression material. Other substances which set harder and cannot be cut are of no use.  There is no reason for these impressions to be made using a tray of the kind that dentists use, which takes an impression of the outer surfaces of the teeth.  The outer surfaces of the teeth play no role in the production of speech, so they can be neglected.  All that is needed is an impression of the inner surfaces of the teeth and roof of the mouth.

The following is one possible process to making the impressions:

        Mix the Jel-Trate with water in a bowl using a spatula.

9        Don’t use when it’s still runny. You must be able to pile the mixture. If it runs out the sides, you won’t get the whole palate and it could be unpleasant for the subject.

        Heap the mixture on a mirror or other flat surface, or in an appropriately sized dental tray.

        Have the subject lean forward, so that if the material does run out, it will not be swallowed.

        Insert the mixture into the mouth, press up against the palate and teeth.

9        You want to push up until you feel the bottom of the impression material to be on the plane of the teeth.

        Hold in this position until set (by color change, if you are using color phase dental alginate, or by timing+touch).

        Remove the tray from the person’s mouth and remove the impression from the mirror/tray. (Fig. 5)

        Trim the base of the impression so that it is flat and in line with the plane of the teeth. If necessary, trim the excess from the back and sides. (Fig. 6)

        If you need to store the impression, you can wrap it in a wet, moist paper towel.

Fig 5: The dental impression being removed from the mirror used as a molding base.

Fig 6: Excess material is trimmed from around the plane of the teeth.