Places where software should never fail: Your Dentists

There are certain places where software should never fail. Obvious ones like aircraft, missile control systems etc. Well here's a new one: when you are lying in a dentist's chair, mouth wired up, with a tooth freshly dremeled away, and the dentist and his assistant are staring, speechless, at their special PC's screen.

This was my position earlier this week. I was having an onley done (I was not familiar with the term, its kind of mid-way between a filling and a crown: they remove a bunch of your tooth, but not all of it). Before they started they put this thing in my mouth that was connected to a special (Windows) PC. Turns out it was taking a 3D picture of my tooth. Once they had ground away much of that same tooth an hour later, they took another 3D picture of what was left. The PC was then supposed to "diff" the two 3D images, and work out what exact shape to make the replacement tooth-part. I say "supposed" as in my case the software said "No, can't do that". This was the point where my dentist was silently staring at his PC's screen, and the point when I was getting even more nervous.

The dentist explained that the "before" picture, the one of my original tooth, didn't work for some reason, and of course that tooth was now a thousand small parts down the drain, so trying to take the picture again wasn't an option. He said he hadn't seen this happen for years, so instead of using a picture of my original tooth, he would use the "database" and find someone else's tooth that was similar to mine, and do the diff manually. This he proceeded to do: I watched for 20 minutes while he edited the tooth, in cool rotating-3D (a bit like those NASA simulations of a planetary surface), so it matched the "after" picture of my tooth. I asked him to carve my initials in the top of it, but he declined (said something about ethics or some such). With his 3D modeling done, he clicked a button and an automated lathe-type device in the back room proceeded to create my replacement tooth. I was impressed with the technology, so they let me go back and have a look: it took a small rectangle of porcelain and proceeded to carve it using a couple of tiny blades and a lot of distilled water. 17 minutes later, as predicted by the PC, the job was done and the tooth was fitted: it fit perfectly (they said: hard for me to tell).

If you plan on getting one of these procedures, make sure your dentist is computer-savvy: that 3D modeling required serious trackball dexterity as well as the usual dialog-box driving skills of any Windows program.