You probably have to do something really blatant for them to really say you were cheating. I pointed at the screen to get numbers correct, I even touched the screen to brush off dirt to make sure it wasn't part of the picture(something I think prometric people should do before hand).
My thinking is this the prometric people does a random sample or flags people they think are suspicious(during their checks) in some way and reviews the tape and reports it to the ADA or whomever is in charge for test that person is taking.
It is like any mass production of things, small random samples are tested.
Think about it. there are what 12000+ dental applicants, probably a few thousand more test takers who don't apply because of scores. Not including retakes. You can't possibly review everyone. the ADA doesn't have the time to review all 4.5 hours of every applicant. 200 dollars(well 300 now) isn't gonna cover it and still have a huge profit.