Well into the second half of the 20th century, crowns placed on teeth towards the back of the mouth were always made out of gold, and those on front teeth were made from a fairly weak ceramic called feldspathic porcelain. These solutions were the best available, given the technology and materials science of the time.
Gold was a convenient solution for restoring back teeth, as it’s undeniably a very strong material, but aesthetically the results were not pleasing. For front teeth, the feldspathic porcelains available at the time looked good, but were not particularly strong and had an unfortunate tendency to break –usually when least expected, and inevitably at the most socially awkward moment!
A significant advance came in the 1960′s through the efforts of researchers in the UK : it became possible to fuse porcelain to a metal inner layer, so that the crown was tooth-coloured, but had the reinforcement of metal inside. Unfortunately, early versions of this type of crown suffered with fairly poor appearance, as disguising the metal beneath the surface layers of porcelain was difficult to achieve.
These porcelain fused to metal crowns (PFMs) are still used at both the front and the back of the mouth but, as dental technology has improved, it is now possible to achieve much more aesthetically pleasing results.
It is also now possible to make very strong, tooth-coloured dental crowns without any metal inner layer being used at all, using the latest alumina and zirconia -based ceramics