In Chapter 4 of Night, what were the objectives of the medical examinations?

The objective of the medical examination was purportedly to determine which of the prisoners was fit to work.  The objective of the dental examination was to determine which of the prisoners had gold teeth.  If a prisoner had a gold filling or crown, his name was added to a list, and in a few days he was summoned to see the dentist again, so that the gold could be removed.  Gold was a metal which had great value; the gold extracted from the prisoners' mouths was taken for the benefit of the Nazis.

When Elie arrived at Buna, he and his fellow prisoners had to undergo "medical inspection".  The prisoners were sent in the early morning to be examined by three doctors seated on a bench in the open air.  The medical part of the examination, at least in Elie's case, was cursory; the first of the doctors "was content merely to ask, 'Are you in good health?'"  No one would have dared say anything other than the affirmative.

The dentist, however, was much more thorough in examining the prisoners.  Unlike the doctor, who had barely looked at them, the dentist ordered the prisoners to "open (their) mouths wide".  His objective was not to find teeth that needed repair; the dentist himself had teeth that were clearly badly rotted and untended.  The dentist "was not looking for decayed teeth, but gold ones" (Chapter 4).