P.E.
Does the chipped tooth bother the child or just Mom? If the dentist says it is okay, just the looks are off, leave it alone, Do not bring up the subject to the child to make him selfconscience. Make up a pretend story.. While I was chasing king kong, he dropped me and my tooth chipped, but we're still buddies. It's so far fetched that it isn't a lie but a make believe story.
Mom you have the problem not the child, get over it! And hopr that is the worse thing that ever happens to him.