By Kevin Kim………… I evaluate about 40 cases per day. Five of those 40 cases may have inadequate impressions. In the morning, with my coffee in hand, I can easily spot them without even sifting through the work tickets. They’re demarcated with a square yellow paper with a big red stamp that says “Kevin” and a handwritten note that reads “Please evaluate impression and call doctor.”
A technician has asked me to consult with the doctor because he feels that this case might result in a remake. After checking the impression and evaluating the model, nine out of 10 times he’s right.
We’ve all heard the term, “Garbage in … Garbage out.” Meaning, if you send me a bad impression, you’re going to receive a bad crown. There’s no sugar coating that statement, but in real life,it’s true. As a technician,the next time you see a bad impression, take a step back and ask yourself:
Can I pour up this impression like any other impression? Yes.
Can I connect the dots on the die and take a guess where I think the margins are? Sure.
Can I make a gorgeous crown that seats perfectly on the model? Absolutely.
Will it be accurate and functional in the patient’s mouth? Probably not.
So before all that time and work goes wasted into fabricating this restoration, it’s my duty to save us all the future headache and just make the phone call. I’ve found if you simply ask for a new impression, the doctor will send a new one uncontested. However, there will be instances where the doctor cannot take a new impression due to time constraints (i.e., a wedding or a vacation).
When I see impressions that look like the outcome will be compromised, I make a mental note, but I have them poured up anyway. This will show the doctor we at least made a conscious attempt at pouring up his impression. The resulting model will reveal where the discrepancy is. At this point, I’ll give the doctor one of four options:
Take a new impression. (Recommended!)
Send the model and die(s) for doctor to die trim. More often than not, the doctor will realize a new impression is necessary.
Fabricate the framework and send for try-in. This is for impressions that aren’t that bad but need to be checked to see if the margins are sealed.
Proceed the case to finish but at “no guarantee.” In other words, the doctor will take full financial responsibility if the case comes back. This option comes into play during those time-constrained cases I cited before.
The technicians in our lab often ask me how I approach my doctors without offending them for a new impression. It’s actually quite simple.
In the instance where a doctor gives you a problematic impression, don’t blame him … Help him. Show that you are genuinely concerned about his patient and his practice by giving him recommendations and solutions. Here are a few important suggestions I convey to my client that help him understand why this impression went awry:
Please make sure to completely dry the prepared area before applying the wash material. Blood, saliva and other moisture captured in the impression create distortions on the model.
For margins that yield the best result, I recommend using the twocord technique for isolating margins. A combination of #00 and #2 cords provide adequate retraction for a clear exposure of the margins.
Retraction cord that contains epinephrine will cause deterioration or unset margins in some impression materials. Thoroughly rinse and clean the prepared teeth before injecting the wash material.
If using “sideless” triple trays, check to see the patient did not bite into or onto the tray. Otherwise, the bite will be off, and the doctor will lose precious chairtime adjusting the occlusion.
Preparations need to be smooth and without undercuts. Make sure there are no rough preps, large voids, bubbles or really sharp angles that will impede the impression material from getting to the margins and the sulcus.
Use a sturdy, rigid impression tray. Flimsy plastic trays designed for bite registrations should not be used for your impression as they are prone to distort when placed under occlusal forces.
Keep in mind tray size is very important. Single unit cases are okay for quadrant arches but for anything three units or more, I strongly suggest using a full arch impression. These cases require more adjacent and opposing dentition to properly articulate.
In closing, I would urge doctors to double-check your impressions before dismissing the patient and certainly before boxing up the case and sending it to your lab. A word to the wise, as my plaster manager (Steve Tapie) always says, “Time spent on the impression is time saved when you’re chairside.”
On the other hand, we, as lab technicians, should inspect the impression closely upon receipt and before pouring up the model. If the doctor sends us a perfect impression, there’s no reason we can’t fabricate a perfect restoration.