I'm currently volunteering/shadowing at a dental clinic set in a hospital, and I think it's been a great experience for me personally (part of it is just the friendly atmosphere of everyone there)! My school's volunteering organization has a program specifically for hospital units, and the dental clinic is one of them. I like to see the dentists and residents interact with each other and the patients, and I think it's great to see dentistry in a non-private setting as well (a bonus for me is that there is always someone to shadow since there are 4 dentists on the floor and 2 residents). As said above, it's the same type of dental work you'd see in the private clinics, but you may have opportunities to ask the residents questions about schools and the things they're doing since they know you're in the process of working to become a dental student too.