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Figure 9: As I look at the lower anterior teeth, I realize the bite problems
are getting bigger because this patient spends some serious time with
these teeth in contact with the uppers. Every once in awhile you will see a
case like this with an anterior open bite, but if this isn’t one of these cases,
this bite will drive the patient crazy.
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.
While double-arch impressions can be suitable for one
single-unit crown or two single-unit adjacent restorations,
they should never be used for a bridge.
A Disastrous Double-Arch Impression Tray41