I work in a dental institute(post graduate mostly) the main thing I got asked at my interview for a band 4 dental nurse interview was regarding any post qualifications I had or would be willing to do, also in our place the nurses are expected to work in any department if necessary so if your dental hospital is the same they'll probably ask what you know about different specialities such as oral surgery/ medicine, paediatrics (with sedation) restorative (implants?) and orthodontics.
They'll ask what you do in your current job,I'd just make sure you know what services are provided in the hospital so you'll know what's expected of you.
Good luck with your interview! .