I don't know too much about the program or how competitive it is, but here's the website (Oral Health Sciences).
http://www.bumc.bu.edu/gms/oral-health-masters/
I'm pretty sure the classes you take will count towards your first year at BU, so if you take biochem/physiology and then attend BU dental, I don't think you have to take those classes again during D1 which opens up a lot of free time and stress.
I took one class from this program because I am a BU employee and can take a free class (figured it looked good for dental schools apps). It's a smallish program (40?) so everyone was really close and they were all super friendly. Even though I'm not in the program, the director helped me in a mock interview and basically told me what interviewers at BU Dental school looked for.
Also, most if not all the students are applying to dental school so it's really geared towards dental school applicants. If you have any questions, don't be afraid to e-mail the director (Dr. Davies). She's amazingly helpful and always seems to be full of energy, haha.