small teeth/gaps

Question
I rescued a puupy a couple of weeks ago.  We think he is a some type blue tick/pit mix approximately 3-4 months in age.  His joints were swollen and his teeth seem underdeveloped for his age (we are raising another pup as well and we were comparing the teeth of the two dogs).  His teeth are small with many gaps and no sign of growth since we've had him.  Is there anything we should be looking for or that we could do to help him along.

Answer
He could have some problems from past poor diet.  I would put him on a dog chow and little else unless a vet examines him and finds he needs something else.  Dog chows are carefully formulated to give a dog the complete and balanced diet it needs.  Adding supplements is likely to do more harm than good by messing up the careful balance.  there are exceptions, but best determined by a vet that has examined him.