Our endo prof gave us the following instructions:
"Protocol for preserving the extracted teeth: (better follow the protocol if you do not want the teeth to crack during the procedure)
1. To disinfect the teeth, dilute household bleach in 1:5 (1 part bleach + 4 parts water) and soak for 2-3 days.
2. Keep the teeth in a mixture of following solution: 2 parts of bleach + 3 parts of glycerin (from cvs or Walgreen) + 5 parts of water."
I modified this a bit and used about 1/3 bleach solution and kept the extracted teeth in that for a while (some of them over a month), until I got around to transfering them to the bleach/glycerin solution. I bought the glycerine at the drug store, it was in the facial products area--apparently used as a skin softener. It keeps the teeth from becoming brittle. It worked well and I had no problems with brittle teeth, but heard of others' teeth fracturing and chipping.