Rex, unfortunately I do not have access to exocad dental database to give you exact instruction, but it is on the main dental DB screen. Select the check mark? Settings button? And you will see it in there. Hope that helps. Been awhile.
If you never make a decision then your possibilities are endless.
In the exocad program right click in the background, scroll over "view" then click settings like Jason said. You'll see "Tooth library to use" and a drop down menu where you can pic the default.