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!