While you don't work on animals in dental school, there's a very good chance that you'll have to do cadaver dissections. While it seems gross, it's actually pretty interesting, and a great learning method.
If you want to do research, there is a good chance that you may work on animals though, depending on the experiment. I worked with hamsters in my research lab.
Yes we do experiment on animals, specifically the Homo sapien species. Luckily, we abide by the highest ethical code and have not had any inhumane treatment occur at our facilities. Sure there may be unplanned drillings or the occasional accidental pulp exposure, but nothing too traumatic. Have I mentioned yet that these animals volunteered to be "experimented" on?
In all seriousness, the only time you would be experimenting on animals if you elect to become invloved in a research lab involving animals.