I've gone to two dental schools, where they offered a sim clinic in which I was allowed to hold handpieces and work on typodonts and what not. So to answer your question in these cases I have spent extensive hours in them
Hmmmm from the sounds of it, it doesn't sound "extensive." In my opinion, extensive would be 50+ hours. If you just visited once and they let you in there then I wouldn't really put that on my application. If you spent many hours in them, I would place it under dental experience.