Dialogue vs narrative to convey ideas

ok any serious writers out there?

I have a question... First let me say that in the last few years I've switched from descriptive narrative to dialogue in order to explain things to my readers.

The advantage of this is it allows me to inject an idea into the readers mind far more efficiently. However, a novel mostly comprised of dialogue may seem boring after a while! Terry pratchet manages it quite well but I'm concerned.

Any ideas?