Making an accurate representation of your preparations is paramount for well-fitting fixed prosthetics. This article describes a simple, 1-material, 2-step impression technique. The technique is a modified version of Dr. Schoenrock’s laminar flow impression. A single material is used for both the tray material and the secondary wash material. The material used is Affinis Monobody (Coltene/ Whaledent). The rigid D&D tray (Superior Dental and Surgical Manufacturing Co) is the tray used. Steps in taking this simple and accurate impression are as follows: (Note: Steps 1 through 3 are accomplished prior to final tooth preparation.) (See figures 1 through 6).
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| Figures 1 through 6. Steps in a simple and elegant 6 impression technique. |
Step 1. Try in the D&D tray for passive fit; soft and hard tissue should not be impinged.
Step 2. Load the selected tray with Monobody. The loading is easy but may take a little practice, since there is no cloth or separating membrane with the tray. Turn the tray 90° from horizontal and “walk” the Monobody onto the tray from back to front, keeping the mixing tip in contact with the material at all times. It is simple to move the mixing tip from the top of the tray to the bottom while expressing the Monobody in a continuous ribbon of material; the Monobody has enough body to stay in the tray.
Step 3. Place the loaded tray in the patient’s mouth and have him close to centric occlusion (CO) position. Remember that the patient has already practiced closing with the tray in place at the tray try-in step. Monobody is easy to bite into/through, so having the patient close to CO should not be a problem; there should not be any deflection on closure. You may stabilize the D&D tray for the initial set of the Monobody by placing your second finger on the chin notch and letting the tray handle rest on your first finger. When the Monobody has set (approximately 5 minutes), remove the tray by holding the tray handle in one hand and supporting the mandible with the other hand. Your thumb will be placed in the chin notch while your fingers cradle the rest of the jaw. Tell the patient that on your count of 3, you will press down on the tray handle and he should open his mouth. Remove the impression with a snap. (Note: Step 3 is best accomplished while waiting for anesthetic to take effect.)
Step 4. The impression is rinsed with water and set aside. When the tooth preparation is complete, take the initial impression and drill 2 holes through the side of the material, one in line with the mesial-buccal papilla and one in line with the distal-buccal papilla. The holes can be made with a No. 6 lab bur or a 3/32 drill using a slow-speed straight handpiece. Clear debris from the holes by blowing clean air through the holes. Make sure the impression is clear of all debris. You may wish to run a lab bur along the gingival margins of the preparation to give more bulk to wash material in that area. Take the intraoral tip that inserts into the mixing tip and cut about a third off the tip. Insert the intraoral tip into the mixing tip and attach it to the Monobody cartridge. Rinse and dry the prepared tooth, place the readied impression back into the patient’s mouth, and instruct the patient to close. Place the intraoral tip into the most distal hole in the impression and inject Monobody until you see it extrude from the mesial hole. While injecting, remove the tip and quickly place it in the mesial hole and inject until you see material extrude from the distal hole. While injecting, remove the tip from the mesial hole and let the material set (approximately 5 minutes). Remove the tray as before and examine your impression.
CONCLUSION
This article has described a simple, single-material impression technique that can give you superb results. As with any impression, care must be given to proper gingival tissue management and good tooth preparation design and finish. Affinis Monobody is an addition reaction polyvinylsiloxane material. Therefore, sulfur-containing compounds must be washed clear before the second step. The initial impression should be clean to make sure there is good adhesive of the Monobody to the initial impression (Step 2). A clean, dry cotton swab can be used to wipe the initial impression. This technique can reduce material inventory and give you confidence that remakes will be a thing of the past.
Dr. LaMond is a general practitioner in Milford, Ohio. He received his dental degree from Loyola University Chicago College of Dental Surgery in 1982. He completed a general practice residency at Miami Valley Hospital in Dayton, Ohio, where he remains on staff. Dr. LaMond has given impression technique lectures to national audiences. He can be reached at (513) 248-0565.
