Nicole, I don't know if this is the route you would want to go, but since you are talking about baby teeth and not permanent teeth, you might want to consider having the tooth removed instead of having the dental materials in the mouth. Of course, your son is so young and will have to wait so many years until the adult tooth comes in...
If the materials used are relatively non-toxic I suppose it's fine but if it becomes a problem again in the future you might want to consider pulling the tooth. Just a thought.