Difficult to know exactly how a specialist interview for Dental Nurse will go as it is - well, very specialist! However, I reckon you can expect them to ask you about techniques, especially ones relating to the Nurse rather than the Dentist, so a check of your technical knowledge and how you apply it. Something like 'What do you think of the new advice on the Wilkinson technique for calming fearful patients?'. They are likely to be opinion based questions rather than something like 'Name the chemical composition of a 2.4 ratio general amalgum' (Can you tell I'm not a Dentist yet?)
They might also ask a few questions about the hierarchy in the surgery, ensure that you are confident enough to speak out if you think there is a problem even though the Dentist is an Officer. Also that you are comfortable and confident dealing with patients of all ranks.
They may also ask about deployed operations, working from field units to see if you could cope with working in far from perfect conditions.
In the main it is likely to be looking to see if you have considered the differences between being a Dental Nurse in a surgery in Bradford and one in Basra, and will be assessing your answers to see that you could cope.