The Black Line Around Your Crown, Explained

You look in the mirror, smile, and raise an eyebrow. There’s something off—a thin black line where an older crown meets your gumline. Is it decay? An infection? Pause. Before you panic, take a breath. It’s usually not what you think! Keep reading to see what’s going on around your gumline and learn how your dentist can fix it.

The Metal Underneath Is Showing Through

Many crowns, especially older ones, are made from porcelain fused to a metal base (also known as PFM). This design is great because it combines the strength of metal with the natural appearance of porcelain on the surface. However, it does have a small drawback. Over time, as your gums naturally recede, the metal edge at the base of the crown that’s normally hidden can become exposed. That thin strip of visible metal is what creates the dark line you’re seeing.

Why Are My Gums Receding?

Gum recession is extremely common and usually has specific causes behind it, including:

• Brushing Too Hard: Aggressive brushing or a stiff-bristled toothbrush can wear away gum tissue over time.
• Gum Disease: Inflammation from plaque and tartar weakens the attachment between gums and teeth, causing tissue to pull back.
• Tooth Position: Teeth sitting slightly out of alignment often have thinner gum coverage, increasing the risk of recession.
• Clenching or Grinding: Excess pressure on teeth can strain and weaken the supporting gum tissue.

Is It a Problem?

Visually, many patients simply don’t love the look. Functionally, some gum recession isn’t dangerous on its own, but it can be a sign that something is going on that needs investigation. Recession can also change how the crown fits, so a checkup is a smart move any time this line appears.

What Can Be Done About It

The most common fix is replacing the older crown with a newer, all-ceramic one. This type of restoration doesn’t rely on a metal base, which eliminates the dark line entirely. In some cases, addressing the underlying gum recession needs to be part of the treatment plan, too. A consultation is the best way to find out which option makes sense for your smile.

If you’ve noticed this line on one of your own crowns, don’t ignore it. A quick evaluation can put your mind at ease and help you decide if it’s time for an upgrade. Your dentist will be there to help you every step of the way to make your smile shine.

About the Author

Dr. Nasim Doroudgar is a dedicated dentist who graduated with honors in endodontics from Augusta University’s Dental College of Georgia, where she also earned the Golden Molar Award. With over a decade of experience and a passion for complex dental cases, she offers natural-looking, metal-free crown restorations at Lux Dentistry in Alpharetta. Call (678) 404-5005 to schedule your consultation today.