Hey Hysteria, if you are sure your stats will get you into dental school with your year off, then go with option #2. You mention specializing in your post and by working for a year for a dentist, you will have the chance to learn what the specialties are all about in the real world and make a better decision as to which one you might want to pursue someday. I am currently a third year and am thinking about specializing, but I barely have time to shadow/assist practitioners to make an educated decision as to which one I definitely want to apply to at the end of this year. What we learn about each specialty in school is not enough at all to really know what they do on a daily basis in a private setting. Even though you will be working for a general dentist, you will be familiar with dental terms and procedures and learn so much more working for him than you will doing alcohol research. It will also keep you motivated to finish school b/c sometimes it is hard to see if it is worth it in the end when you are struggling as a dental student in Anatomy lab.
Yes, specialties want to see research. But how much they want to see and whether or not research done before dental school "counts" is a very difficult question to answer. Here's why I don't have a good answer. Last year, three seniors applied to ortho from our school, top ten students. They did 4 or 5 weeks of research junior year summer and all got in. That was the only research they ever did - "resume research." When I asked these students about their research committment, they said "oh, programs just want to see that you did something, they don't care how much." One of these students was in my lab and didn't even know how to use the automated pipet and didn't put in even half the time I did on my project for 8 weeks. But he is now in an ortho program, which was his ultimate goal anyway. I'm sure there are specialty programs that might look for more substantial research than 4 weeks, but students at my school have been doing "resume research" and getting into specialties for many years now.
We have students in our class who did option #1 or #2 prior to starting dental school. With #2, if you hang around your first choice school and eventually get in, you will have an advantage over your classmates by knowing the faculty and upperclassmen and how policies and procedures work.
Unless you need the masters to bolster you credentials to get into dental school, save 17 grand and earn some spending money for first year. Good luck with your decision!