No, they have no usage. I couldn't sell my Organic text at the end of the course b/c they changed the edition. I haven't touched it since. Now it's only good for a very heavy bookend. General bio I sold as soon as possible and I have never missed it. Same goes for Physics and General Chem. I did look at the Biochem text a little when I was studying for boards. But I could have just looked in my dental school biochem book if I wanted. Unless you have books from undergrad subjects that you are taking again in dental school (Physio, gross anatomy, histo, biochem, micro, pathology, neuroanatomy) don't bother keeping them. Even these are of questionable value b/c you may use a different text or a graduate level text rather than the undergrad level text. You'll never look up a Grignard reaction or solve a derivative again.
I would keep the textbooks which cover subjects covered in dental school (griffin mentioned those subjects). Sometimes, the required text is the text that you already own. Also, your old text could be a good reference if you don't want to buy a textbook for a particular class (buying every single book that the prof requires/recommends becomes very pricey and not cost effective).
Unfortunately some dental schools are moving to electronic texts and those schools will force you to buy all the texts on a DVD for $1700 a year whether you like it or not. The school Griffin and I are attending (Univ. at Buffalo) does that, plus another 5 schools. The useability of the electronic text is another (very long) discussion..
P.S. to Griffin04: Heya classmate! Didn't know you hung out here.
Class of '04
UB School of Dental Medicine
The one reference textbook for "hardcore" biochem that I used throughout the years is the Biochem bible itself: Stryers.
Used it when I took biochem in undergrad, again when I attended a MS/Biology program, and used it occasionally in dental school (though the biochem course we took in dental school concentrated more on regulatory mechanisms and not on the individual structures of chemicals, THANK GOD!!).
All in all, Stryers is an excellent biochem reference text.