Figure 1: When walking through Glidewell’s crown & bridge department the other day, I stopped to ask a technician what one thing dentists do in cases they send to the lab that drives him crazy. “I’m glad you asked!” he said, and handed me this impression.

Figure 2: Looking closer at this impression, we can see that it is for a 4-unit bridge, but it was taken in a double-arch tray. I learned from Dr. Gordon Christensen many years ago that this is a no-no, and now this technician wants me to know that he dislikes this technique just as much as Gordon does.

Figure 3: Turning the impression, we can see that the prep was in contact with the tray — another no-no. As hard as it may be to believe, all it takes is one point of contact like this between tray and prep to prevent the entire bridge from seating properly.

Figure 4: The impression itself around the splinted abutments is so-so; tooth #29 appears to have a void on the facial and the lingual margins, while tooth #28 has some very thin material on the facial and distolingual margins. This always makes me nervous as we pour the die stone because the material is heavy enough to bend those margins.

Figure 5: The margins on tooth #31 also appear thin and friable, and it’s hard to tell definitively whether tissue retraction took place. Using the Two-Cord Impression Technique, or to a lesser degree by using a diode laser, we can create enough lateral retraction to end up with a big, thick margin on the impression that won’t distort.

Figure 7: Here is the poured model of the impression. It looks like we have enough reduction for the BruxZir^® bridge (Glidewell Laboratories) the doctor prescribed, except for on tooth #28 perhaps. I would have prescribed a PFM bridge, but that is another story. I am still concerned about the bite because there aren’t any stops distal to the bridge.

Figure 8: When I spin the articulator around and view the case from the anterior, my fears are confirmed. I have a hard time believing that the bite from the impression is correct. I cannot believe that the patient only bites on that cuspid. Without any unprepped teeth on the opposite side to hand articulate, the situation looks dicey.

Figure 10: A little twist of the articulator brings the other two anterior teeth into contact, but now there is a huge gap between the posterior teeth. Again, there is no way to verify where the bite is correct. If only we had a full-arch impression on the upper and the lower, we could take an educated guess.

Figure 11: Look at all these wonderful wear facets; usually, these make it a no-brainer for us to hand articulate a case. Even a separate bite registration over the preps could have saved this impression — if you ignore the fact that many bridges made from double-arch trays don’t fit. Bottom line: This case needs to go back to the doctor for new, full-arch impressions.

Figure 12: As I was leaving the technician’s workstation, he also handed me these full-arch impressions. I was instantly suspicious when I saw the trays the dentist used. Do you recognize them? You do if you do Invisalign^® (Align Technology Inc.; San Jose, Calif.). These are the plastic trays you have to take Invisalign impressions in so that the company’s X-ray scanner can read through the trays.

Figure 13: I thought we had seen it all when it comes to impressions, but this may be a first. It’s a 3-unit bridge impression on the lower, but the dentist took what looks like a half-arch impression with a full-arch tray. There is also some material placed on the other side of the tray to impress two molars and a bicuspid. Was this done purposely?