Crown Preparation

Last molar on bottom right showed hairline crack in x-ray; never had any pain or discomfort, but dentist convinced me the old amalgam should be removed and the tooth prepped for a crown...he said it is possible we may have to do a root canal.  I allowed him to go ahead and drill.  He told me that there was still an evident crack below his drill but that he did not want to get too close to the nerve, so he stopped and apparently packed the tooth and put the temp crown on.  Why was my tooth not built up for the crown....should I be waiting around for that tooth to become instable or filled with bacteria, or should the dentist have built up the tooth to seal the crack?  Or is he correct to wait and see?

[Jerome Bogin, D.D.S.]

It may not need to be built up for a crown to be placed and there is nothing wrong with having a temp on for awhile.