Franken-scope
Actually, this is pretty cool. Professor Jeffrey Hillman of the University of Florida may just have eliminated tooth decay.

Tooth decay is caused by bacterium that live in the mouth and feed on the sugar that remains on your teeth when you don't brush. Dr Hillman has genetically altered these bacterium and produced a variant that doesn't produce the acid that causes decay. In animal testing, the mutant bacterium displaces the native form, eliminating a lifetime of tooth decay with a single inexpensive treatment.

Wow.

And I immediately thought of a science-fiction novel, Steel Beach by John Varley, in which the Central Computer that runs the Moon solves this problem essentially the same way. It's a small scene in a 500-plus page book, so of course I can't find it just this minute. But I wonder if Dr Hillman has read it?

LATER: Found it. Early in the book (page 116 in the Ace paperback), Hildy sarcastically asks the CC to do something about "the way my mouth feels when I get up in the morning before I brush my teeth. We're so goddam advanced, you'd think we'd have done something about that by now, wouldn't you?" Well, Hildy's in a Mood, and not expecting anything to come of this.

Some days later (page 205), Hildy wakes up with a mouth that tastes like peppermint. The CC explained:
"You asked me to work on that. I did. ...I synthesized a nanobot that goes after the things that would normally rot in your mouth while you are sleeping, and changes them into things that taste good."
"I'm afraid to ask how you slipped this stuff to me."
"It's in the water supply. You don't need much of it."
"So every Lunarian is waking up today and tasting peppermint?"
"It comes in six delicious flavors."
"...Do me a favor, don't tell anyone this is my fault."