When Buddy was about 14months old I took him to the vet for something
unrelated to his teeth. He did, however, have one lower tooth, the pointy
one on the bottom
still there along with the new one. The vet said
it needs to come out because the adult tooth will not go in the right place and will always be out of line with his jaw. Also, when it was removed there was tartar in back of it because I could
not get to it due to the teeth being double in that area. So there are
a couple of things to consider. Your best bet is to ask the vet.
At 14mos the tooth was still very secure in place so they might not
get loose at all. You want the new teeth to be in their right place in the mouth and that won't happen if the baby teeth are not removed.
Also tartar will build up on the adult teeth because you can't brush between the double teeth.