Why are my gums turning dark purple or black around my dental crown?

Dark gums around a dental crown are usually caused by the metal in an older crown showing through the gum tissue. This is a common cosmetic issue and not a dental emergency. Less often, the discoloration may be caused by gum disease, metal particles trapped in the gums or a problem with the tooth under the crown. The cause will determine whether treatment is needed.

What you'll learn in this article:

• A dark line around a crown is usually the metal inside an older porcelain-fused-to-metal crown showing through the gum—not a problem with the tooth.

• Purple or swollen gums around a crown are often an early sign of gum disease and should be checked before the problem gets worse.

• All-ceramic and zirconia crowns don't contain metal, so they won't create a dark line at the gumline.

• A dental provider can identify the cause of the discoloration and explain whether treatment is needed.

If you're noticing dark or discolored gums near a crown, schedule an appointment with an Aspen Dental provider for a personalized evaluation.

What causes gums to turn dark around a dental crown?

Several different things can make gum tissue near a crown appear dark, purple or even black — and the causes look different from one another once you know what to look for.

Is the metal inside your crown starting to show?

This is the most common cause and usually the least concerning and it's a cosmetic issue, not a health problem

Many older crowns are made with a metal core covered by tooth-colored porcelain. These are called porcelain-fused-to-metal (PFM) crowns. The metal extends to the edge of the crown, where it's normally hidden just below the gumline.

As your gums naturally recede or change over time, that metal edge can become visible. The result is a thin gray or black line where the crown meets the gum—not a change in the gum tissue itself.

If the appearance bothers you, your dental provider can replace the crown with an all-ceramic or zirconia crown, which contains no metal and won't create a dark line at the gumline.

Could metal compounds be staining the gum tissue itself?

Yes, although it's less common. With some older crowns, tiny metal particles can collect in the nearby gum tissue over time. This creates a dark gray or bluish spot in the gum, not at the edge of the crown, but within the tissue itself. It may look like a bruise that never fades.

This is called gingival tattooing. It's harmless but permanent; it won't fade, and removing the crown won't reverse or remove the discoloration. Your dental provider can determine whether the crown should be replaced to help prevent further staining and discuss options if you're concerned about how the area looks.

What does it mean if the gums look dark purple and feel sore or swollen?

This is a different situation. Healthy gums are firm and pale pink. When bacteria build up along the gumline, the gums become inflamed, turning dark red or purple. They may also feel sore or bleed when you brush.

Around a crown, this often happens when the edge of the crown doesn't fit tightly against the tooth. The small gap can trap bacteria, and plaque can build up more easily if the area isn't cleaned well.

The good news is that gum disease is very treatable when it's caught early.¹ Because it often doesn't cause discomfort at first, changes in gum color may be one of the first signs you'll notice. If the gums around your crown look dark purple, feel tender or bleed easily, schedule an appointment with your dental provider rather than waiting for your next routine cleaning.

Can a problem with the tooth under the crown cause dark gums?

Yes, but it's less common than the other causes.

If the tooth under the crown has died, the changes inside the tooth can sometimes cause the tooth to turn gray or create a purple shadow beneath the surrounding gum tissue. This looks different from the thin dark line caused by a metal crown. Instead, the discoloration appears to come from underneath the gums.

A dead tooth doesn't always cause discomfort, so a change in color may be the only sign. An X-ray can show whether the tooth under the crown is still healthy. If treatment is needed, such as a root canal, it can often be done without replacing the crown.

When should you see your provider?

A thin, stable dark line along the edge of an older crown is usually just the metal framework and doesn't require urgent attention, though it's worth noting at your next visit.

Seek an evaluation sooner if you notice:

• Gums that are dark purple, swollen or bleeding around the crown

• A shadowy discoloration that seems to come from inside the tooth or beneath the gum

• Throbbing or tenderness near the crown

• A sudden change, or any change that seems to be getting worse

How is gum discoloration around a crown treated?

Treatment depends on the cause.

If the dark line is caused by the metal edge of a PFM crown, your provider may recommend replacing it with an all-ceramic or zirconia crown for a more natural appearance.²

If gum disease is the cause, a professional cleaning—or a deeper cleaning if needed—can remove bacteria and reduce inflammation. Early treatment usually protects both the tooth and the crown.

If metal particles have stained the gum tissue, treatment depends on the extent of the staining. Laser treatment may improve the appearance in some cases. Your dental provider can explain your options.

How can you prevent gum discoloration around a crown?

Cleaning carefully around the crown edge (brushing gently along the gum line twice a day and cleaning between teeth daily) removes the bacteria that cause gum disease before they take hold. An electric toothbrush is particularly useful for reaching the crown margin without applying excess pressure.

When it's time to replace an older crown, choosing a metal-free material from the start eliminates both the metal margin problem and the risk of gingival tattooing.

If you've noticed dark or discolored gums around a crown, your dental provider can identify the cause and recommend the treatment that's right for you.

Why are my gums turning dark purple or black around my dental crown? FAQs

If you're still wondering why the gums around your crown changed color or whether it's something to worry about, these answers can help.

Will my insurance cover replacing a crown because of a dark gum line?

It depends on why the crown needs to be replaced. Dental insurance is more likely to cover a new crown if there's a clinical reason, such as gum disease around the crown, a dead tooth underneath it or a crown that no longer fits properly. If the crown is functioning well and the dark line is only a cosmetic concern, replacement is usually considered elective and may not be covered.

Do all dental crowns cause dark gums?

No. Porcelain-fused-to-metal crowns are the most common source of dark margins because of their metal core. All-ceramic and zirconia crowns don't have a metal substructure, so they don't produce a dark line at the gum edge. If you have an older PFM crown and are bothered by the appearance, ask your dental provider whether switching to a metal-free option makes sense for you.

Could dark gums around my crown mean there's an infection?

Possibly, though not always. If the line is stable and hasn't changed, it's usually the metal margin, not an infection. But swelling, throbbing, a bad taste or discharge near the crown are signs that need prompt attention. Contact your dental provider right away.

Sources

¹Mayo Clinic. "Periodontitis — Symptoms and causes." https://www.mayoclinic.org/diseases-conditions/periodontitis/symptoms-causes/syc-20354473

²Cleveland Clinic. "Dental Crowns." https://my.clevelandclinic.org/health/treatments/10923-dental-crowns