To answer your question directly, I have 3 C's (non-science) on my transcript. Don't trip too much on the Orgo grade...we have LOTS in our class that made B-/C in O-chem. You will never use the crap again, so rest easy. I would recommend you make every other aspect of your app very strong. Get a stellar DAT score, excellent LORs, and have lots and lots of clinical shadowing hours and volunteering. You may want to take some upper level bio classes (genetics, immuno, histo, anatomy, physio, biochem, etc...) and get all A's in them. You do have a lot of C's...which is not good. One or two isn't a big deal, maybe three if one is in a non-science subject...but that many is on the brink of trouble. Just a word of advice, they don't really give a crap about how hard/reputable your school is. I too ran into the same problem and thought like you, but it didn't matter at my home state school, from which I was rejected. If you do not pay attention to anything else I say, please listen to this. MAKE YOUR APPLICATION UNIQUE!!! We had almost 3,000 applications last cycle and only 100 seats. That's 1 seat for every 30 people applying. Stress to them over and over why you would make a better student for their program than any others. Pay attention to the strengths of the school and mold yourself to their core beliefs, i.e.-"your school has a very well-known clinical program and that's what I value most in getting a dental education" -or- "I have always wanted to give back and I realize your school does mission trips/community service more frequently than most" and things like that. Always pay attention to this, they want you to be happy at their school as well.
About dental school (read if you like)
Unfortunately, the science classes you are taking now are VERY watered-down versions of what you will see in dental school. I am a D1 and I never thought school would honestly consume this much of my time just to pass. I went to a very difficult private school for undergrad and I never made anything less than a B+ in my science classes (Bio major). When you get to dental school, you would be just absolutely astonished how hard tests are. You can honestly study for four-six hours per night the whole quarter and feel on top of things and when you take the midterm/final, you feel like you MAY have known half of the questions.I'm pretty sure it's about the same everywhere, but in my first quarter I have taken Restorative Dentistry I Lect/Lab (learn how to wax NOW!!!), Biochem, Medical Physiology, Histo, Gross Anatomy (from hip up), Embryo, and applied clinical anatomy (i.e., heart murmur, sleep apnea, asthma, etc...) lectures. I say all of this to say this, if you think competition is fierce now, wait until you hit D1. I seriously study 5/7 nights per week until about 2/3 in the morning...just to make B/C range.
Don't let this scare you, it did me at first. Some people, myself included, will never be wonderful test takers, no matter how much we study. The faster you learn to accept this, the easier your life will be. Grad school tests are so much different than undergrad it's unbelievable. Here, just knowing the info (fact recall) will get you at best ~40%...in undergrad it was more like ~80% (for me at least). If you've never left a test feeling like you got 50% of the questions right at best...get used to it. It really pisses you off when you study so much and the professor just intends on doing this. You will adjust, and if your dream is to become a dentist, nothing can stand in your way. Just be realistic in the expectations you hold yourself to. I am happy with B's and I know I don't have the agility or the brain power to make all A's. When you guys start dental school, you will seriously be amazed how much info is covered and how it will sneak up on you and bite you in the a*$. You see, in undergrad...I could study on the weekends and get by. Not here, it's just too much to digest. For example, in gross anatomy (if you wait to study until the weekend)...you will go over four lectures that week. For us, it was shoulder, axilla/pectoral, arm/forearm, and wrist/hand. We had to know every single muscle, it's innervation, function, insertion/origin, etc. It would be ok if this were your only class, even then it's a stretch trying to learn/retain that in one weekend. Add on Physio for five lectures-Pulmonary, Renal, Endocrine (omg horrible lol), Cardio, and one more lecture. TONS of formulas you need to learn to manipulate and lots of things that are tricky (certain numbers you have to know when/when not to use). Restorative for a week-two or three wax quizzes, tooth IDs, projects, etc... and then the lecture for Restorative-Incisors, Canines, Premolars, Molars, Primary Dentition....and there you have it. This hasn't even included you going into the lab to work on the cadaver/look at Histo slides.
What do I recommend? Just take it one day at a time. Get a good planner and work everything out to where you're most efficiently using your time. Find a schedule and STICK to it. Your whole first qtr will be a good time (hopefully for you) to learn HOW to study. Again, I was very surprised how different studying for undergrad was from dental school. So, do I enjoy what I do? Yes, I absolutely love it and I hate it as much as I love it...weird huh? You will meet some awesome people in dental school, everyone is in the same boat as you and you learn to make it together as a team. Also, as crazy as everything sounds above, you have to make your priorities straight. If you have a family, don't neglect them completely. I pick two nights/week to take off and spend with my wife, go out to eat, watch a movie, whatever. On my short lecture days, I study all day/night. On the days I have Resto Lab until 5pm I don't study because my brain hurts and I am just too tired to hold anymore. All in all, just be ready to adjust and try to find what works for you. We all study differently, and we break off into group studies based on how we study. Some people (I hate them with everything I have) can memorize the lecture just sitting in it one time (no BS)...some (like me) have to absolutely beat the info into their brains, and others in between of course.