Try and get some experience in a dental hospital, or in a maxillofacial or orthodontic department of a general hospital. You could volunteer with a charity like the British Red Cross. If you can afford it, there are plenty of volunteering opportunities abroad too!
I'd recommend you also do something for yourself during the year, like learn an instrument or work to earn some money, or even some travelling. Universities like people who are well rounded, and don't just focus on getting in.