Here's my contribution. I just spotted this contest...
Although I would like to tell you my thoughts on your current pick - most of your picks actually. People in general are afraid of the dentist so any teeth imagary does not bring pleasent feeling for them. What you should embrace is your name ALEGRE which means happy and do something in this direction with a smile. Not only because of the name, but also because of the fact that people with beautiful teeth smile more and that is what you should (could) communicate to your patients/clients to make more pleasent experience when the spot your brand name. Of course with all this said you should also portray the professional side.
Hope you find what you are looking for and hope you don't mind my comment.