Personally, and this is just me. I dont like quantifying volunteering in "hours." Honestly, when it comes to volunteering, I would just stay involved throughout college, dont make it look like a last ditch effort at the end. Also, take on a few big projects of volunteering instead of dabbling in everything just to make it look like a lot on your application. For instance, try getting really involved with a group or two on campus and work your way up to an office and make it your own, do great things with it, not only does it show leadership but commitment to a project and pride. I think it sounds silly to say well I have 200 hours of volunteering, it just sounds to me really disconnected and thats not what volunteering is about.
Now on the other hand, shadowing is another thing. That you basically have to quantify and should because it just shows you've got some serious hours of shadowing and getting the hang of how a dental office works. It also shows you have a relatively good idea that you really want to be a dentist.
Theres my 2 cents!
