Triple trays are excellent for saving time and money for your crown impressions. But they can also be the cause of misfit and excessive adjustments if not used properly.
Here are three tips that help me use them more effectively:
(1) Support the most distal tooth with rope wax
If you’re taking an impression of the most distal tooth in the arch using a triple tray, there is nothing to physically contain the impression material where you need it most. This doesn’t matter if you’re impressing a tooth in the middle or anterior. However the most distal tooth requires that support to prevent the material from pulling in crucial areas like the margin.
Note the pull on the disto-buccal aspect of the margin
That’s no bueno.
So I take a piece of soft rope wax and create a flange around the back. Simple and definitely more cost effective than relining or retaking the impression.
Use of rope wax supports the impression material around the tooth
(2) Try in the tray first!
Before I take the impression, I’ll have the patient bite into the triple tray. Obviously you want to ensure that the tray is the appropriate length and width. But a more subtle factor to consider is how the patient will bite. Some people instinctively protrude their mandible when asked to close; I’d like to know this beforehand!
This patient cannot fully close with a triple tray. Abandon ship!
(3) Avoid the triple tray when not indicated
I use the triple tray for a maximum of two units and if sufficient teeth are present. I never use it for a bridge because there is an increased risk that the abutment teeth will not be recorded in the correct relation to each other. Also if there are multiple missing teeth I’m concerned about accurately recording the bite.
Feel free to post comments about any other triple tray tips you’ve discovered!