Hi Tina,
In short - yes you can. Some dental schools around the UK will accept access to medicine.
And now the long answer...
I would strongly advise and suggest you research which dental schools accept it before applying and also their UKCAT and GCSE policies. I assure you - you do not need additional A-levels. In addition, Kings only accept applications via access from people who have been out of full time education for at least 5 years.
City and Islington do run additional A-levels! They can, space permitting, fit you onto an AS chemistry course. Hope that clears up the confusion?
My advice is sit your UKCAT good and early, then email and call every single dental school in the U.K and check their policy on all 3: access, GCSE and UKCAT. It will become apparent the best places to apply for - especially with a good UKCAT. I'd also strongly advise you contact the college and attend the open day(s) and speak to Amy/Imran in depth about your likelihood of success.
If you have any other queries, shout me!