Showing some tooth as part of the Happy Smile is not big deal. It's when the lips are retracted and the hair rises that it becomes a concern (like my part Chesapeake).
My Black Lab has big white teeth (that's all they can see, 'cause NO light is reflected by the dog) that scare folks (who obviously don't know Labs) when she smiles the Happy Dog Smile.
I’ve been owned by Chessies for the last 27 years and they do indeed smile. Most people, however, don’t realize that it’s just a smile and, depending on the person, I often don’t tell them what the dog is doing.....LOL Just rescued my newest one, a 20 month little girl named Emma. I LOVE Chessies!!!