I’ve had a few requests from readers about how I splint impression copings together after my post on passive fit.
There are two reasons you might do this:
(a) You’re about to take an open tray impression of multiple adjacent implants and you want extra accuracy.
(b) You already have a model of the implant positions and you want to fabricate a verification jig.
Some people do both (a) and (b). It’s kind of like wearing a belt and suspenders at the same time, but hey, passive fit doesn’t come easy. More recently, I’ve been doing this a little differently, but more on that later.
Okay, so whether you’re doing this in the mouth or on a model, the steps are the same.
(1) Insert open tray impression copings
Yes, they have to be open tray copings.
If you try to take a closed tray impression of splinted impression copings, you’ll lock in the tray. Uh oh.
If you’re making a jig on a model, closed tray impression copings also tend to extend longer into the implant, which is less forgiving of angle discrepancies. For example, look at these impression copings from Nobel Biocare:
Note the difference in sub-platform length between closed (left) and open (right) impression copings.
(2) Tie a slip knot in dental floss and loop in around one of the copings
Slip knots are used in sailing for tying a rope to a post or bar, which is just like what we’re trying to do.
Dr. Jeff Kopman taught me how to tie a slip knot. You’ll have to practice a few times, so here’s a video:
(3) Weave the floss around the other copings
This will create a matrix of dental floss for the next step. Tie it off when you’re done. Not much to say here; this is pretty straight forward, folks.
Neoss impression copings before and after floss.
(4) Apply GC Pattern Resin
This takes some patience. I dab powder and liquid, back and forth. Be careful to not let the resin touch the gingiva; it may irritate or scratch tissue. Also, don’t let it interfere with the screw so you can still take it out.
Application of GC Pattern Resin to floss and impression copings.
(5) Wait 15 minutes
The resin may look hard, but subtle changes occur for about 15 minutes. Rushing this step could lead to inaccuracies. If you’re using Duralay Pattern Resin, allegedly you’ll have to wait longer for full setting.
Completed splinted impression copings.
So I’ve been trying something new for multiple adjacent implant restorations recently. I just take a fast and dirty closed tray impression, and make a verification jig on the resulting model. Then at a second visit, section the jig in the mouth (because it won’t fit), then reapply resin to the tiny slices I just made to get it to seat passively.
Why do it this way? It saves the time of splinting intra-orally, which is a pain. There are also some lecturers that say that splinting intra-orally has inaccuracies, hence why we do a verification jig afterward in the first place. At least this way we are only applying small amounts of GC resin intra-orally, thus controlling the amount of distortion. What do you think?