I think what you may want to look into is an SMP, a masters program designed to get students into dental or other health professional schools. These programs are normally designed to mimic a similar science course load that you would expect from dental school and are used as a way to show that you are capable of handling a dental school curriculum. They are generally pretty pricey but can be very helpful if you do well in them, as far as getting noticed by dental schools (getting interviews) and getting you accepted. A lot of them have articulation agreements with the dental schools they are affiliated with which can really make a difference in whether or not you get in anywhere. And yes, you can and should apply during the year of your masters so you hopefully do not have gap year after it.
Of course, you can always do the post bacc route as well and just take classes informally.
There is a forum that talks about the different SMPs and such on here, that might be helpful for you to read through and get an idea of what kinds are out there.