alginate set, and correctly remove the impression tray. Use the following steps to take preliminary impressions:
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 fit.
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 patient&'s 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 seal.
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 occlusal plane.
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.Continue Reading