The piece of tooth has now vanished altogether - apparently when Keith ate a grape. Doubtless it will reappear via another orifice but I don't think he'll be looking!
So the sander had to be brought into operation. It seems to have done the trick for now.
In spite of post-it stickers left in various places to remind him to ring the dentist today, the dentist has not been rung.
Far be it from me to say that men are wimps but I leave you to draw your own conclusions.