You could ask your dentist. Also if you have a relative who is a dentist or have family members that have a friend that is a dentist, that would help.
With no connections, simply call or e-mail as many dentists as you can. I'm sure there are plenty of dentists around your neighborhood. Another option is to actually show up at the clinic and tell them you are interested in shadowing/volunteering.
You'll get a few rejections, but keep trying. One of them will be nice enough to take you in.