dog grinning

Question
Hello, we have a sweet, fiesty 1y/o pit bull terrier mix.We adopted her from the shelter at 6 wks of age. She is an energetic, determined individual who like lots of attention.She does have canine and human playmates and lives a fairly gentle existance(sleeps on bed, etc.) It is hard to convince visitors and babysitters that she means no harm. She has a habit of showing her teeth-almost a grin, usually when she is very excited. I read in the book 'How to Speak Dog' what this means, but I can't find the resource now. I'm pretty sure its not agressive, but I need to convince, sitter, sitter's mom, husband of this.  Please help with resources.
Sophia will be eternally grateful.
Thanks

Answer
Dogs DO "grin", and this can be a fear grimace, a sign of affiliation (usually subdominant or submissive), or a signal of dominance. The fact that she does this when she's excited insinuates that it is an anxious behavior (which can mean she's not in control of her cognitive processes at that moment.) I suggest you read Turid Rugaas book:  "On Talking Terms with Dogs"; I also suggest you put into place some strong signals of your authority in this situation by introducing positive reinforcement training.  Visit ClickerTraining.com and teach this dog one very strong behavior ("Sit", but use a unique word) to get started.

The fact that she "likes a lot of attention" tells me she's getting a fair amount of FREE attention, and sleeping on your bed is psychologically promoting her.  If her "grin" is anything but just that, you are looking at a possible problem (I CAN'T SEE THAT FROM HERE.)  Once she has obtained a VOLUNTARY (no collar, no restraint) response to your command for "sit" and does it every time, ask her to work for everything (Nothing In Life Is Free) for the next two months.  Do not allow her onto the bed except by YOUR invitation: remove her when she jumps up there by simply taking her collar gently and saying "off".  If you have not initiated her presence there (by patting the bed and saying "up" or any other word you choose), do not allow her access.

Sophia's breed has gotten a very bad reputation, and somewhat deservedly, not because of the breed itself but because some of those who breed them are outright miscreants themselves, breeding without any knowledge of genetics or inheritability and breeding for all the wrong purposes.  You know nothing about this dog's genetics: were her dam or sire fearful, aggressive, what sort of whelping situation did she come from, why did she end up in the kill shelter, was she bottle fed or forcibly weaned from her dam, etc.  Erring on the side of caution is the best approach; there are MANY MEMBERS of her breed in the population at large and MOST of them are fine companions.  Take this dog into a training scenario (group class) with an experienced trainer using ONLY positive reinforcement and continue her socialization while expanding her willingness to "work".  Advise your visitors and relatives that this is a very young dog NOT LIKELY to show any aggression toward humans without serious provocation and each time they hesitate to interact with her they teach her about THEIR FEAR, which is very bad for her.  You can't make people like or trust your dog; all you can do is work with her to make her the best possible companion.