Don't worry about it! If you can get a good picture of how dentistry works in those days it will show.
Theres loads of great advice in other posts on here, havent read it all but i'd say /add / repeat...:
Ask about NHS 2006 contract, new contract that is supposedly coming in based on capitation and quality, their thoughts on it. Ask about provision of treatment, Fluorides, Composite vs amalgam, dentures, implants, all that basic stuff.
Also know what is happening at your dental school of choice too - they often have a home page with info on what is happening there, though this varies
Tell them about your interests as they will ask you. If you play piano say to what standard, have you done any performances / just for pleasure and so on. I remember I talked about it in my interview when they asked me ,since i play piano too. They were more interested in that than the dental stuff! though it varies uni to uni i'm sure