Flexing Blu-Mousse with no rebound
It’s all in the timing! no retraction, no hemostasis, and 5 minutes start-to-finish
by Thomas J. Schoen, DDS
Wabasha, MN
When a patient occludes into a conventional double-arch impression, the plastic tray may distort. That’s not necessarily a problem.
If the impression remains distorted when the tray is removed from the mouth, you’ll get an accurate impression.
On the other hand, if the tray snaps back to its original shape, you’ll have major problems at the seating appointment. The restoration will fit the die, but there’ll be a lot of grinding before you get it seated in the mouth. You may even have to remake it.
Over the years, journal articles have offered a number of hints to reduce snap-back distortion in double arch trays.
Use a metal double-arch tray
Use a rigid material: Once it sets, super-rigid Blu-Mousse tends to lock the tray into the distorted position, reducing the chance of snap-back.
Use a rigid wash: Dr. Rod Kurthy recently described using rock-hard Mach-2 as the wash in Schoenrock’s Laminar Impression technique. This further stiffens the impression.
De-Program the tray: Some dentists cut the tray’s posterior connector immediately before seating the impression to eliminate the tray’s memory.
Go trayless: And a few years ago Dr. Kent Mattison described his “no-tray” technique using Blu-Mousse and Green-Mousse. No tray - No tray memory.
But even without a tray there’s still a possibility of snap-back distortion. For example, I found the idea of the trayless H&H impression very attractive. In my hands, 100% of the H&H impressions looked fantastic. And 100% of the crowns required adjustment.
Think about it: once it has set, impression material itself has a memory. When the impression is reseated in the mouth for the wash step, the material may distort - because it’s not exactly in the original position ... or it may distort under biting pressure… or it may distort because the hydraulic force of compressing the wash material forces the flanges apart.
Now if the force of the primary impression (I’m referring to Blu-Mousse here) exceeds the resistance of the flexible wash, even a trayless impression may snap-back when it’s removed.
A memory test
Express a straight line ribbon of Blu-Mousse Classic (2-minute set) onto a mixing pad. Set a timer as soon as you finish expressing. When the ribbon loses its tackiness (around 2 minutes), you will find the ribbon is flexible. Shape it into an L shape and hold it there an additional 2 minutes. What was once a straight line ribbon is now an L shaped ribbon, and does not return to its original straight shape. Try and straighten the L and it will spring back to the L shape
A memory-less impression technique (No tray, no retraction, no hyper-compression.)
For the past 4 years I’ve been using a trayless impression technique that reseats the primary impression for the wash step before it develops a memory. It’s a little like Dr. Hoos’s H&H technique - and a little like Dr. Mattison’s trayless technique. The primary difference is timing.
Like the test on above, in this technique you fabricate a tray with Blu-Mousse, distort that tray while it is flexible, and hold it in that shape until it is firmly set in the new distorted shape.
So far I’ve taken at least 2000 impressions using this approach, and the results have been terrific. The entire impressing procedure takes me 5-minutes start-to-finish.
As with most techniques, the margins must be visible to be captured in the impression. But I routinely use curettage diamonds for my marginal prep, ensuring that the tissue is away from the margin. The moderate force of the wash step effectively flushes away moisture and blood. So I no longer use retraction cord. (I do sometimes use Expasil® for facial veneers or for patients on blood thinners.) If there’s extensive bleeding I staunch it using Ultradent’s Astingident® X with infuser. But minor bleeding won’t cause problems.
I honestly believe I could take this impression under water. So far, however, I haven’t had a patient volunteer for the experiment.
The Technique: Step-By-Step
Timing is very important with this technique. The only piece of equipment you need is an easy-to-read, easy-to-reset timer. Before we begin, I want to emphasize that this technique requires Blu-Mousse Classic ... NOT Blu-Mousse Super-Fast.
1) After completing tooth preparation, express the Blu-Mousse Classic into the mouth. (I prefer the OLD cartridges to the new ones because the old mixing tip express a wider ribbon of material.) Express the Blu-Mousse directly onto the preparation. From there, keeping the tip of the mixing tip in the material, cover the teeth in the arch in a zigzag fashion. (Figures 1-3) Have the patient bite into maximum intercuspation. (Being trayless is a big advantage here, as the Blu-Mousse offers almost no resistance to deflect the bite.)
2) You want the Blu-Mousse to set in the mouth for 90 seconds, but have the assistant set the timer for 2 minutes. (I’ll explain why in Step 3.) While the Blu-Mousse sets, the assistant prepares the wash.
3) When the timer shows “30 secs” remaining, the assistant resets the timer to 3 minutes. You do NOT want the bell to go off because too many patients have some kind of Pavlovian response to the bell. They open automatically!)
At this 30 second point, tell the patient to remain closed while you see how the impression is setting.
It should be rubbery to the touch. If it’s mush, wait another 15 secs and try again. If it’s hard, start over.
If the impression is properly rubbery you’ll have a bit less than 30 seconds to complete taking the impression.
4) Hold the impression against the arch that contains the prep, so it remains on the teeth. Then ask the patient to open. (While you’re learning the technique, you may do this too soon. As a result the material may stick to the teeth or the buccal may separate from the lingual. No problem. Just have the patient close and push the lingual material back into place with their tongue. Count to ten and proceed.)
5) Quickly express a ribbon of wash material (I use Imprint II®) into the opposing impression and have the patient close (Figure 4).
6) Without waiting, have the patient open again. This time, help the impression remain on the opposing quadrant (Figure 5) so the preps are exposed.
7) Using your 3-way syringe, quickly spray and dry the impression. Check the preps for debris or clots, and rinse and dry them as well (Figure 6).
8) Add a ribbon of wash to the entire quadrant. To minimize the chance of trapping air, place the tip deep into the impression so you’ll fill from the bottom up.
9) Ask the patient to occlude firmly (Figure 7). Once occluded, ask the patient to push his tongue against the lingual. While he’s doing that, you simultaneously compress the buccal by pressing against the cheek. Then tell the patient to relax into light occlusion as before.
10) As the patient closes, the assistant resets the timer for the wash, places her palm beneath the patients chin and maintains light pressure to prevent movement.
11) The impression is removed when 30 seconds or less remain on the clock. You’ll discover the impression is surprisingly rigid. (Figure 8) A word about the wash -
I’ve tried a number of different materials for the wash with this technique. The one that seems to provide the best bond to the semi-set Blu-Mousse is Imprint II Quick-Set.
This technique produces excellent accuracy. Of course, it doesn’t provide the massive compression of the H&H technique. You can’t count on it to force the wash subgingivally. (But unlike the H&H technique, it doesn’t require 5 coats of spacer to get the crowns to fit.) However there’s more than enough compression to push fluids out of the way. This technique works well with cord as well…no syringe is needed, plus a little bleeding is ok…you will get a beautiful voidless impression time after time, even in the presence of bleeding. I’ve even used this approach for full arch-impressions. (Not recommended till you’re fully up to speed with the technique.) But that’s the subject for another article.
For more information about Blu-Mousse, click here. 
About the author: Dr. Tom Schoen has been an active member of the Wabasha MN community for 22 years, serving as president of the Jaycees, KC’s, Rotary Club, and Chamber of Commerce. He has 6 children, Ages 18 to 4. He has a family practice covering all phases of dentistry , including orthodontics. He invites all to visit the “Home of Grumpy Old Men”. He can be e-mailed at tschoen@lakes.com.
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If you get the timing right, you can bend a stripe of semi-set Blu-Mousse - and it will complete setting in the new distorted shape. Here’s how I used that fact to improve my impressions...
Figures 1-3: For this technique the older Blu-Mousse tip works better because it lays down a wider ribbon. This makes it easier to cover the quadrant quickly using a zig-zag pattern.
Figure 5: Immediately, hold the impression on the opposing arch and ask the patient to open again to expose arch containing the prep.
Figure 6: Clean and dry both the impression and the preparation.
Figure 7: As the patient firmly occludes, he pushes his tongue against the lingual material while you press gently against the buccal.
Figure 8: About 30-seconds later the impression has set.
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