I recently had my first root canal -- while it wasn't all the painful hell I'd expected, it was far from pleasant. What I didn't know was, the entire content of a tooth's pulp getting cleaned out and replaced by plastic rods wasn't The Worst Part (TM). That lucky title comes several appointments later, and goes to the preparation for placing the crown upon said tooth.
Apparently, in about 25% of cases, there needs to be something called crown lengthening. Some people, like the young lady featured in the before and after pictures of this link, have crown lengthening performed on many teeth at once for esthetic reasons. I, like many root canal patients, needed it to prepare for crown placement.
You see, when I was a lad, I had many amalgam fillings placed in my molars. Of course, in the last ten years, they've posited that the mercury content in run-of-the-mill amalgam is cause for everything from kidney failure to parapsychotic episodes. (My wife, luckily, doesn't read Scientific American, or she'd probably be able to use all that silver in my mouth as grounds for divorce.)
Anyway, what they do is, they scalpel the meat perpendicular to the gumline for a few millimetres, the peel it away from the tooth. If that weren't enough, they then shave the jawbone to meet the contour of the tooth. After all of this, they sew the gum back together, minus that millimetre or two of flesh. Probably the most disconcerting parts of the procedure itself were aural: the sounds produced by the grinder and suction taking away bits of jaw-meat are nothing less than gruesome.
Here's a pretty extreme look at what I had done -- mine was only the width of one or two molars, with a single stitch to close it up. Still, under the bubble-gum pack that acts as a mouthal bandaid, this is what I have goin' on to the immediate stage right of my tongue.