I've had a look at each of those 3 Dental schools for you where Welsh Bacc counts as an A level.
Please read the Dental Schools Council booklet for information for each dental school btw- you can then check if other schools accept Welsh Bacc . Liverpool is okay, but Leeds for example says contact them for advice on other qualifications
Presumably you are resident in Wales? That gives you contextual status for a Cardiff application, which is a huge help.
As for a B- unless contextual, or applying for a Foundation Year, I think all courses are AAA minimum. But surely it's too early in Y12 for predictions? And you have the 3 other subjects to get the As.
Good luck!