Is it normal for a brand new crown (not yet attached to tooth) to break when asked to bite down on it?

Hi Edwina,

So sorry to hear that your crown broke when your dentist was trying it in. The fact that you said that it broke in half tells me that the crown was most likely an all ceramic/porcelain crown. This type of crown does not obtain its full strength until it is fully bonded onto the tooth, and is subject to fracture up until that point. Most likely the crown was high in occlusion (its bite), or was not seated properly, and the compression force cracked it. In addition, crowns need to be of a certain thickness to prevent fracture. If the dentist did not reduce the height of the tooth enough during the preparation, before the impression, then the ceramic would be too thin, and it would fracture. So, as you can see there are multiple reasons the crown can fracture, and it may, or may not be something that your dentist has done. I would give them another chance to remake the crown, and I am sure you will have a crown that will last you a very long time. Best of luck. 

Was the crown a permanent crown or a temporary crown?

Temporary crowns are acrylic, if it is to thin, can crack easily.  

If the crown is a permanent crown, cracking of the porcelain is not normal during insertion.  However, certain factors could have caused the crown porcelain to crack:

1.  Imperfection or impurity in the porcelain which caused a weak area.  

2.  Inadequate reduction of tooth resulting in a thin area of porcelain and weak spot.  If this is the cause your dentist must reprep the tooth to provide adequate room and thickness of porcelain.