The lava 3m:                                                                           

is a variation of all-porcelain. It is made out of all ceramic, but rather than being cast and made by a laboratory technician, its scan by a computer in the dentist's office.

Then its finish on the laboratory by technician to full porcelain the advantage is that no metal involved and its perfectly fits 100%.

Are also a variation of all-porcelain which uses the non metal full porcelain . Other ceramic materials are Procera, In-Ceram, zirconia, and feldspathic porcelain. A good cosmetic dentist will be familiar with all of these materials and will use the best crown for each clinical situations.  

Are nearly natural appearance, subject to two limitations. Because they have a metal framework underneath, they require the use of an opaquer to cover the metal, which makes it impossible to fully re-create the translucency of natural teeth. They also eventually will show a dark line at the edge, next to the gum. Dentists try to hide this line under the gum, but sometimes they are unable to do this; and sometimes the line doesn't show when the crown is first placed but shows later, as the gum recedes. They can also create a porcelain butt margin that tends to minimize this dark line, but it doesn't eliminate it.