If you were not convicted and the charges were dropped, then you should be able to get the case dismissed. If the terms you use are correct, then by definition you did not commit a crime and are not considered guilty. However, given that it's still on your record, this will play a role in everything you do from the moment you apply to dental school to when you apply for your license. Most organizations do not have access to files that have been sealed, but depending on the state, schools and health institutions will still have access to records even if they are sealed. Talk to a lawyer about your case, and do whatever you can to get it off your record.
Also do a search for any details regarding background checks and applying to dental school. This question has appeared several times in the past couple of months. Closing thread as it's already a duplicate.