It seems that his dentist was leaving the group he was in and was moving out of the area. On the final visit with my friend a full set of x-rays were taken and my friend was given a clean bill of health. Six months later, my friend was examined, with new x-rays, by a new dentist, in a different practice, closer to his home. He was told that he had a cavity that needed to be filled and that he had a crown that was "leaking" and needed to be replaced.
My friend took the new x-rays back to the old dental practice and was examined by one of the doctors in that group. My friend was told there was no new cavity and that the crown in question was not leaking.
My friend was confused and did not know who to trust. I gave him the following scenario: You pull into a gas station and the attendant tells you that your tires are all worn out and you need to buy a new set from him right away. You drive straight to a tire dealer and after examining your tires, you are told that they are fine for another 10,000 miles. Who do you trust? The dealer that wants to make a sale or the one who tells you that you don't need anything at this time?
Most people know more about tires than dentistry... Get a second opinion!