Ok first things first. Ask anyone on here who is a graduate. Becoming a dentist after doing a degree first is.
1) Way more competative, as there are less places and loads of applicants.
2) Way more expensive, as you are not entitled to a second student loan so you have to fund the entire 4/5 year degree yourself. Around £45,000 in tuition fees alone.
3)A very long road, at least 7/8 years before you start earning any money.
My advice to you would be, Resit your exams if you get BBCC. Get your AAA and apply as a first degree undergrad for dentistry. You might need to take a gap year, but it's a better idea than doing a degree first trust me.
You can do a degree and get in, but beware, there are still A level requirements for some unis and in some cases you will be in direct competition with undergraduates. So it isn't a get out clause if you do poorly in your A levels. You'll need a 2:1 / First in whatever degree you do aswell. Usually it needs to be a science related degree.
If you're serious about dentistry, you need to start doing lots of work experience and voluntary work, along with an activity to provide evidence of good manual dexterity. You also need to consider the fact that you will have to start revising for the UKCAT exam aswell.
Also with those grades BBCC, you might find it difficult to get onto a Pharmacy/ Biomedical science course aswell, i think most ask for A/B in Biol/Chem. I'm not very clued up in this area, you're better off talking to the people in the respective forums. But if you don't manage to get into one of those degrees either. Then this could begin to get quite difficult. However, having said that, you've done the right thing in coming on here to ask for advice and help. If you'd like to ask more. You can PM me, or anyone else on here. Most people are more than willing to help and most have already been through the process and so have a good idea about what it entails and what you need
Best of luck !!!