Porcelain-Fused-to-Metal (PFM)
Porcelain-fused-to-metal dental crowns (PFM) are somewhat of a hybrid between metal and porcelain crowns. When they are fabricated, the dental technician first makes a shell of metal that fits over the tooth. A veneering of porcelain is then fused to this metal (in a high-heat ceramic furnace), giving the crown a white tooth-like appearance.
The metal that lies underneath the crown’s porcelain can sometimes be visualized as a dark line found at the crown’s edge .We usually try to position this dark edge just underneath the tooth’s gum line. But, if the gums happen to recede, or if it is very thin, the dark/ metallic line can show, thus ruining the crown’s appearance.