(Read some of the previous sections.)
If your patient uses denture adhesive, make sure all of it has been removed before the final impression. The adhesive has enough body to punch holes in the impression. You have to use a piece of gauze to wipe away the adhesive. Rinsing alone will not do the job.
If possible you would like the patient to leave out the old denture(s) the day before the final impression. This allows the tissues to return to their relaxed state. Leaving out the denture for a longer period of time (a few days) is even better.
Sometimes because of undercuts there is a convoluted path of insertion for the tray. This is especially true of the mandibular arch. Practice inserting the tray without impression material. After adding impression material you will not be able to see the details of the bare tray so the insertion will be more difficult.
The compound should be covered by impression material. THE IMPRESSION MATERIAL MUST EXTEND ON TO THE BUCCAL AND THE LINGUAL.
Seat the tray so that the frenum in the midline is lining up with the "tray frenum." I sometimes put a pencil line on the handle corresponding to the frenum because the impression material may obscure the "frenum cut out" on the tray. (Note the time you first seated the tray.)
After the tray is very firmly seated, wait 10-15 seconds for the material to become more viscous. Start molding the lips over the borders. Look to see that the frena are imprinted.
Wait 6-7 minutes (by the clock) before removing the impression. There is no harm in leaving the tray in for a longer period of time.
Never leave the patient while the tray is in the mouth.
You have to hold the secondary impression for the entire time it takes to set. If you take your hands out of the mouth, and then replace your hands, you will have two impressions.
Patients with a large tongue will thin out the posterior lingual border. Add utility wax to restore the thickness (2-3mm) of the border. There is a tendency to make the border longer with the wax. Just make it thicker.
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©1999 by Julius Rosen, D.D.S.