

I went to the CC and took 5 years to graduate, so that option is always there, but if you're going to be able to graduate without overloading yourself in 4 years I would suggest applying at the end of your junior year and seeing what happens, and if you don't get in, you could stick around and take classes that additional year.
About your bad grade, I had a similar situation, My mom was diagnosed with Leukemia while I was in the second semester of Ochem, and it took a real toll on me and my family, and I ended up getting a D in the class. I retook it later and got a better grade (A C... but whatever, still better!) I then did well on the DAT in that section, and was able to prove to my interviewers that I did learn the material, and that really made up for the bad grade.
There is also a section in the AADSAS application where it asks if anything affected your academic career, and this would be where you talk about your experience. The Adcoms take this section very seriously, and if you show honest improvement and do relatively well on the DAT they will completly understand the few bad grades, and it won't significantly hurt you, and not nearly as much as if you were just flaking off.
Don't stress, I know it is a trying time, but keep on keeping on and you'll get to dental school soon enough! Good luck!
As far as when to take Ochem, I would say take it the year after you finish Gchem, that way you're still in the chemistry lecture / lab groove. As far as physics, as long as you're taking say Ochem, Physics, and maybe a bio elective or something you'll be fine. I wouldn't suggest taking much more than 12 or 13 units though. I took the second half of physics during the summer and it wasn't too bad, but it's very dependant on the teacher.
If you do stay that last 5th year, as long as you've got a full load, 12 units, you'll be good. I've been doing research all year and just finishing up my requirements to graduate, plus microbio this quarter because the dental schools reccommend it, and I said I would on my app.
As far as research, it's definitely not necessary, but it's something that makes you stand out. And even though you are an Econ major, it depends on the school, but you're still taking a significant amount of science classes, and for example at my school UCI, most bio research professors only want you to have completed a year of bio and then gchem or ochem. The key part of getting into research is researching professors and seeing what their projects are about, and then getting in touch with them about research spots - I'd start looking around now if you're really interested, because often research professors require a 1-2 year commitment.
Actually i would suggest email. It is a lot less pervasive and the professor can get back to u when they have time. If u catch them at a busy time on an office visit, they might just brush you aside and that opportunity is wasted. Make it a short email with a cover letter and resume attached. Really make it only a few sentences just letting them know of your interest and attachments. Making it short allows them to read it quickly and decide what to do about it. You can write all u want about your interests in your cover letter.so i'm guessing i can go to the bio department and ask around
so i'm guessing i can go to the bio department and ask around