Is it true that after 100 years of age, human being gets new teeth?

In extremely rare cases, Yes. Mostly, No.

My father, an MBBS general practioner with an OPD of 70 patients a day, recalls seeing atleast three such cases in his 30 years of practice. Interestingly all of these patients belonged to same caste (shepherds), who for a change in India, do not suffer from calcium deficiency due to high milk intake.

It is quite possible that these are secondary teeth which got stuck below other teeth in childhood and did not get the opportunity to erupt then. However, I am more optimistic about tertiery dentition being a reality in exptremely rare cases. I mean we have found teeth in overies.. human body is more complex than we think.

From: Quora