alginate set, and correctly remove the impression tray.
Use the following steps to take preliminary
1. Select the correct size impression tray and
ensure its fit in the patient's mouth is correct. Allow 3-4
mm of space between the tray, teeth, and soft tissues
when the tray is positioned in the mouth.
2. Place utility rope wax around the top border of
the maxillary and mandibular trays to extend their
height. This will also act as a "pad effect" on the soft
tissues. Place the trays in the mouth again to ensure the
3. Mix the alginate and water together in the
mixing bowl with a spatula. Follow the manufacturer's
instructions. Mix into a creamy, smooth consistency.
Use the sides of the mixing bowl and press the mixture
against it to eliminate air bubbles. Total mixing time is
usually 1 minute depending on the type or manufacture
of alginate used.
4. Have the patient rinse with mouthwash
vigorously. This aids in removing food particles and
thick saliva that may cause voids in the impression.
5. As the patient is rinsing, load the maxillary tray
with the mixed alginate. Load the tray with one large
portion of alginate on the spatula using a wiping
movement to avoid air being trapped in the material.
6. Wipe off any excess alginate, and smooth the
surface of the tray with your index finger. Use the
excess alginate from the mixing bowl and place some
directly onto the palate with your index finger before
seating the impression tray. This prevents a large void
within the palatal vault.
7. Have the patient open his/her mouth about
halfway. Using your left index finger, retract the
patients right cheek. Carefully place the filled tray into
the patient's mouth and use the tray to move the left
cheek out of the way.
8. Guide the tray in the mouth and center it over the
maxillary teeth. Pressing up with the posterior border of
the tray, raise the tray to the hard palate area to form a
9. Keeping the posterior border of the hard palate
in place, next raise the tray up over the maxillary teeth.
The tray should be seated so that it is parallel with the
10. Holding the tray in place with your right hand,
use your left hand to gently lift the patient's lips and
cheeks away from the tray until it is completely seated.
The maxillary arch should now be completely
em bedded in the alginate material.
11. While keeping the tray parallel with the occlusal
plane, pull the upper lip over the anterior border of the
tray to form the anterior section of the impression. The
average working time from mixing the alginate material
to this step is 1 1/2 minutes. After this time, the alginate
begins to gel and set up.
12. Still holding the tray in place, look in the
patient's mouth and ensure that no alginate material is
running down into the throat area. If needed use a
mouth mirror to remove any excess. Have the patient
relax and tilt the head down and breathe through the
nose as the material is setting up. A saliva ejector or
patient napkin needs to be in place to catch any excess
saliva while the alginate is setting up.
13. After the alginate has set, place one of your
index fingers along the lateral border of the tray and
press down to break the seal formed by the set alginate
material. Once the seal is broken, carefully remove the
tray from the patient's mouth and wrap the tray in a
moist paper towel. Have the patient rinse his/her mouth
out to remove any excess material left from the
impression. Have the dental officer inspect the
maxillary impression for accuracy.
14. Next, take the mandibular arch impression using
the same basic steps as with the maxillary arch
technique. When seating the mandibular tray onto the
lower arch, have the patient raise the tongue to allow the
alginate in the tray to take an accurate impression of the
lingual aspects of the alveolar process.
15. Once the tray is seated, gently pull the lower lip
over the anterior border of the mandibular tray to form
the anterior section of the impression.
16. After the alginate has set, remove the
mandibular tray in the same fashion as with the
maxillary arch, except push up to break the seal.
17. Have the patient rinse his/her mouth again, and
have the dental officer inspect the mandibular
impression for accuracy. Wrap in a moist paper towel.
18. The dental assistant will now disinfect the
maxillary and mandibular impressions. While in the
DTR, remove the moist paper towels. Rinse and
disinfect using an accepted phenyl disinfectant on the
impression material and trays. Wrap in moist paper
towels again and place impressions in a headrest cover
for transportation to the dental laboratory.