Eliezer is summoned to the dentist because the gold crown on one of his teeth is going to be extracted. The Nazis, in addition to confiscating the money and property of Jews, stole anything else that was of value, including the gold in dental fillings and dental crowns. Eliezer manages to delay the procedure by telling the dentist, whom he describes as a Jew from Czechoslovakia, that he is ill. Later he learns that the dentist has been arrested and is going to be hanged for profiting on his own from the gold extracted from the prisoners. "I felt no pity for him," Eliezer comments, though the dentist had not been unsympathetic to him in twice putting off the procedure.
The episode indicates, though it has already become clear, that Eliezer has become totally numb to the barbarity taking place around him. As with other events, he narrates it in a resigned tone, as if it is not surprising that this sort of thing is going on. It is not even necessary for us to wonder whether dental work was done with anesthetics: obviously, it was not. The dentist himself, Elie tells us, "had a face not unlike a death mask. When he opened his mouth, one had a ghastly vision of yellow, rotten teeth." The description, though it's incidental to the episode, is one more sign of the horrifying conditions of life in the concentration camp.