There are different types of dental crowns. Gold crowns are very durable and strong, which is why they are used in back teeth restorations. All-porcelain crowns are the most widely used type of crowns for their natural look and metal-free composition. Porcelain-fused-to-metal are less costly. They look like natural teeth, although the metal composition may cause a grey colored gum line over the crown. Zirconia Crown are made of a new type of material that provide both excellent aesthetics and strength. Emax crowns are similar to zirconia crowns in strength, look and price.