Die Work
One slip, and I gave myself four extra hours of lab work. Here’s how.
At the School of Dentistry, we are short on cash. (Our dean is also leaving, but that’s a story for another day). So, the students (us) do a lot of intricate lab work in order to make the stuff our patients need (crowns, bridges, etc.). That way, we don’t have to pay a professional lab to do as much of our lab work. This does the following:
- Saves the school money.
- Teaches students (us) what good lab work looks like.
These are good things. However, all of this lab work also:
- Drives me insane.
We use a polyvinyl siloxane (sure you can use polyether, if you want to really bum your patient out) to take a really accurate three-dimensional negative of a patient’s teeth. We then use a special stone (Type IV die stone) to make a positive version of the patient’s teeth in stone.
We then go through a series of steps to produce something that looks like this:
THEN we send it to lab. They take the time to create an entire fake tooth in wax, cast it, possibly porcelain veneer it, and polish.
They are supremely good at this. Incidentally, they’re supremely good at the steps before (the pouring of the cast, the model work to produce that picture above). BUT, us students, who will never do lab work on this scale again, have to try our hand at this stuff. Pretty discouraging, when you make the mistake I did.
If you want the crown to work in the patient’s mouth without adjustments, the whole process has to be completed to tolerances of about 10-100 microns. That’s where my problems started.
I was doing a final trim on a piece not unlike the blue one you see above. There’s a border on it, called the margin, that represents the division between the edge of the crown and the rest of the tooth. I’ve never messed this part up before, but this time I nicked it when trimming. My slip obliterated a piece of margin 0.7mm wide and about 0.2mm deep. I only showed it to a few people, but the consensus was universal: a hole like that is about the size of the grand canyon when you’re doing die work. When hundreds of microns matter, a half millimeter error might as well be a mile.
And so I redid it all.
Comments
Nils +2
Alex, I love the site redesign! I haven’t logged into TumbleDry in a while which makes me a pretty awful person, but I like what you’ve done with the digs. You’re still a great writer and a good storyteller. Keep up the good work.
Alexander Micek
Thanks, Nils! Always happy to have folks back, even after a long absence.