Is There Any Way to Avoid the Circular Band Showing When Getting a Dental Crown?

You can not only avoid the grey band with a CEREC restoration but frequently a ceramic onlay is possible due to the technology.  CEREC restorations disappear in the mouth and allow you to more of your healthy tooth structure and enamel and are therefor more resistant to decay

Full crowns in ceramic materials will avoid the metal band but if the root is dark they can still have the dark band. It is possible to mask a dark root by creating a slot that is filled with light color composite into the root.  There are numerous tricks to enhance ultimate esthetics.

Yes there are many types of crowns. The circular band you mentioned is caused by one of  two things.  The vast majority of the time the band showing is the metal coping of a porcelain veneer crown or PVC. The PVC has been the work horse for natural appearing crowns for decades. The crown gets its name because the porcelain is baked on or "veneered" over the metal crown.  Traditionally the metal has a closer fit to the tooth than porcelain alone can achieve thereby reducing recurrent decay or cavities under a crown which translates to longer life. A dentist can eliminate the metal band showing by preparing a esthetic margin at the time of the intial crown prep appointment or by placing the margin subgingival (belove the edge of the gum).However this offends leads to the second cause of a dark band showing which is caused by the optical differences in tooth verses porcelain. By far the best solution is the new all ceramic crowns which have optical properties very close to natural tooth and can be indistinguishable from adjacent natural teeth to the naked eye.

There are crowns that are made of porcelain fused to metal (PFM's).  This kind of crown may have the metal showing along the gingival margin (the area that meets your gums).  If you'd rather not have this metal showing, discuss it with your dentist.  The prep can be designed so there is no metal collar.  All the best, Dr. Elizabeth Jahanian