PFM (Porcelain-Fused-to-Metal)

What is a PFM Crown? (And What That Dark Line at Your Gums Really Is)

Have you ever looked closely at an older crown and noticed a thin, dark grey line right where the tooth meets the gums? If so, you are likely looking at a PFM (Porcelain-Fused-to-Metal) crown. For decades, these crowns were the gold standard in dentistry—a reliable workhorse that restored millions of smiles.

A PFM crown is a hybrid. It’s built with a core, or substructure, made of a strong metal alloy. This metal interior is then covered with a layer of tooth-colored porcelain to provide a more cosmetic appearance. It was a revolutionary way to combine the strength of metal with the beauty of porcelain.

The Good: Why PFMs Were So Popular

For a long time, PFM crowns offered the best of both worlds and have a proven track record of success.

• Excellent Strength: The underlying metal makes these crowns very strong and durable, capable of withstanding heavy chewing forces. This made them a great option for back teeth and multi-tooth bridges.
• Good Aesthetics (At the Time): Compared to an all-metal crown, the porcelain overlay was a huge cosmetic improvement, allowing for a tooth-colored restoration.

The Compromise: The Downsides of a Metal Base

While strong and reliable, the PFM design has inherent aesthetic limitations that have largely been solved by modern materials.

• The Dreaded Dark Line: This is the #1 cosmetic complaint about PFM crowns. The metal base is opaque, and even with the best technique, it can sometimes create a subtle grayness. More commonly, as our gums naturally recede even a tiny bit over time, the metal margin at the bottom edge of the crown becomes exposed, revealing that dark line.
• An Opaque, Less Lifelike Look: A natural tooth is translucent; it allows light to pass through it. Because a PFM crown has a solid metal core, light cannot pass through. To hide the dark metal, an opaque layer must be applied under the porcelain, which can make the final crown look a bit flat, chalky, and less vibrant than an all-ceramic crown.
• Potential for Chipping: The bond between porcelain and metal is strong, but it is possible for the outer porcelain layer to chip or fracture, exposing the metal underneath.

Today, we have access to advanced all-ceramic materials like Zirconia and e.max that offer the same or even greater strength without a metal base, eliminating these cosmetic issues entirely.

Here's what we want you to remember:

A PFM (Porcelain-Fused-to-Metal) crown is a strong, reliable restoration that was the standard of care for many years. While effective, its metal base creates aesthetic limitations, like the potential for a dark line at the gums, that have been solved by modern all-ceramic materials.

Every patient's situation is unique.

For some, a PFM may still be a viable, economical choice. For others, especially in the smile line, upgrading an old PFM to a new all-ceramic crown can be a life-changing cosmetic improvement. We'll discuss the pros and cons of each material as they relate to your specific tooth.

Have questions about an old crown with a dark line?

Or are you wondering what the best material is for a new crown? We're here to give you honest, personalized answers. Schedule a consultation at our Woodland Hills practice – let's talk about what's really best for your smile.