It's so true what David R. said about not all dentists being knowledgeable regarding oral cancer screening. If you go to this OCF link:
http://oralcancerfoundation.org/dental/index.html - and scroll down a little bit you will see "How to know if you have had a proper oral cancer screening". There is also a section for dentists on doing a proper oral exam. When I first went to my dentist I asked if he did exams for oral cancer and he said "Oh yes, with every patient" but I later found out that he really wasn't doing the kind of exam he should have been. I printed out a bunch of pages from the OCF site which included oral exam information and left it with the office people. The next time I went in he did a very thorough exam just like the description from OCF. He even got a Velscope for his office! (I had left info on that, too.)