Desensitizing toothpaste

In this article: What’s the best toothpaste?, Cecil says

This is a surprising statement, since it certainly works for me. And probably for millions of others. I guess it’s all just a placebo effect…

I’ve been meaning to ask in GQ what the mechanism that NaNO[sub]3[/sub] desensitizes teeth with, but since it doesn’t work, that’s a foolish question. Never mind.

I chose to ignore the pain because it was better than using a toothpaste that tasted like sausage.