Hello,
I'd say it's not difficult to get an interview/job as a trainee dental nurse, as you just need to show that you have qualities they look for (good customer service skills, awareness of regulatory bodies and what infection control is - even if you don't know the details, willingness to learn, interest in the job, reliability, etc.) and be willing to train.
An employer should be supportive in getting you trained, so check that they will do that (even though you must be qualified or on a course to nurse, some surgeries will try to get away with it!).
Also, sorry to sound negative, but find out about staff turnover - if a practice has a high staff turnover then there is usually a reason why.
If you're not sure it's for you, it might me worth calling a couple of practises to see if you can shadow a nurse for a day - they might require you to do a CRB check first, but it will give you an insight into the day-to-day life of nursing.
With the right team, it can be a great job and very rewarding
Hope this helps!