Should New Dental Crowns Fall Off?

If you had six crowns and 2 fell off, you should contact yur dentist right away.  As you have done that, I am surprised that your dentist did not answer. Even though he is in a big group.  Also, to answer your question, "NO" your crowns should not fall off especially just after they were placed.  If you do not like the crowns or the design of hte crowns, let your dentist know. He should have placed them in and let you see them before putting them in permanently. This was you can see whether you like htme or not prior to making them permanent. If I were you, I would go directly to the office and wait to be seen. It shoul dnever be 4 weeks or even 4 days for someone to call you back.  Please do not wait any longer. Your teeth can shift and then the crowns will not fit.  If you are not seeing a cosmetic dentist (Ad it sounds as though you are not) then you may have gone to the wrong person.   

It's certainly not normal for new crowns to fall off within a month of placement. There are many possible reasons for this, there's no way to tell without an exam. You should see your dentist as soon as possible to determine what's going on, or if that doesn't work, find a new dentist.

As a Prosthodontist, I see from your story that you have 2 big problems. One is that you do not like how your final crowns look and second, they are recementing. The look of the final restorations normaly has to be approved by the patient before permanent cementation. If that did not happened with you then you have to address that when you will see your dentist. Crowns tend to recement if they are cemented with temporary cement and they usually do not fall of if they are cemented with permanent cement ( unless something during cementation process went wrong). There is another popssibility that your dentist wanted to try out these restorations because he or she was not sure if you would like it and cemented it with temporary cement, anticipating to finalize it later. But then again it is just my speculation, bottom line you need to see your dentist ASAP and get it resolved.

Good luck!