Maiya,
Try and read articles and book on professional interviews... Body language, dress code... I think it helps a lot.
But most of all it would be great to talk in person with someone with experience on it. I'd recommend someone who conducts work interviews frequently (not necessarily in the dental field, but a professional field) and with someone who interviews well, preferrably in the dental field to give you tips on how to answer the tipical questions.. You can also analyze their personality as you talk to them and kind of try and mimic. People always say " be yourself".. But.. what if you are super shy and kind of a reserved person? That was me... I taught myself how to be more outgoing and learn how to connect with people.. It helped me in so many levels.. even with patients!!!!
There are courses on how to interview where people sort of have a "mock interview" with you too, those can be very helpful if you can't quite figure out what you are doing wrong!
It is like having a personal coach
Hope that helps.. Please dont get discouraged! you got interviews so something is very right about your profile!!!! you will get there!