This is a question that understandably causes concern, and you’re right to ask about it. I’m Dr. Emily Nguyen, Principal Dentist at Picasso Dental Clinic, and I see this issue regularly in my practice. Black spots on crowns have several possible causes, some requiring immediate attention and others being purely cosmetic.
The Most Common Cause: Decay Under the Crown
Decay developing underneath an existing crown is the number one reason I see black spots, particularly near the gumline where the crown margin meets your natural tooth. Your tooth remains alive under the crown, and if bacteria penetrate the seal between crown and tooth, decay can develop.
This happens when the cement holding the crown deteriorates over time, when margins weren’t sealed perfectly initially, or when patients stop maintaining good oral hygiene around the crown. Food particles and bacteria accumulate at the crown edge, work their way underneath, and begin decaying the natural tooth structure.
At our Hanoi clinic, I recently saw a patient with a black spot at the base of her front crown. X-rays revealed extensive decay underneath that had been progressing for months. We needed to remove the crown, treat the decay, and fabricate a new crown. She hadn’t felt pain because decay progresses slowly, but waiting would have cost her the tooth.
If your black spot is near the gumline and the area feels rough or catches your fingernail, decay is likely. If the spot is growing or if you notice bad breath or taste coming from that area, these are additional signs of underlying decay. Don’t wait on this. Schedule an examination immediately.
Metal Showing Through Porcelain
Many crowns, especially older ones, are porcelain fused to metal. These crowns have a metal substructure for strength with porcelain baked over it for appearance. Sometimes the porcelain layer is thin in certain areas, allowing the dark metal underneath to show through as a gray or black shadow.
This isn’t decay. It’s simply the metal becoming visible, which can happen immediately after crown placement or develop over time as slight wear occurs. The crown still functions perfectly fine, but the appearance bothers some patients.
I also see metal exposure when porcelain chips off in a small area, revealing the metal underneath. This creates a definite black spot. The crown is still protective and functional, but the cosmetic issue is obvious, especially on front teeth.
These situations don’t require urgent treatment unless you’re unhappy with the appearance. At Picasso Dental Clinic locations across Vietnam, I can replace the crown with an all-porcelain or zirconia crown that has no metal and won’t show dark spots. Many patients from our 65 nationalities served prefer modern all-ceramic crowns for front teeth specifically to avoid this issue.
Staining at the Crown Margin
The junction where your crown meets your natural tooth can accumulate staining over years. Coffee, tea, tobacco, and certain foods darken this margin, creating a visible line or spot that looks black or dark brown.
This is purely cosmetic and doesn’t indicate decay. The staining sits on the surface and can sometimes be removed or lightened with professional cleaning, though results vary. If the stain penetrates deeply into microscopic gaps at the margin, it won’t polish away completely.
At our Da Nang location, patients often ask if this staining means the crown is failing. It doesn’t. The crown can function excellently for many more years despite surface staining. However, if the appearance bothers you significantly, crown replacement with better margin fit and shade matching solves the problem.
I can usually distinguish staining from decay during examination. Staining feels smooth, doesn’t catch instruments, and appears consistent along the margin. Decay feels rough, may be soft when probed, and often has irregular borders.
Gum Recession Exposing Metal
Gums naturally recede slightly as we age or in response to gum disease, aggressive brushing, or other factors. When gums recede around a porcelain fused to metal crown, they expose the metal collar at the base of the crown that was previously hidden under the gumline.
This exposed metal appears as a dark gray or black line right at the gum edge. It’s not decay, and the crown itself is fine. The problem is cosmetic: you can now see the metal that was meant to be hidden.
Prevention involves excellent gum health and proper brushing technique. Since 2013, I’ve emphasized gentle brushing with patients because aggressive scrubbing causes gum recession that exposes crown margins. Electric toothbrushes with pressure sensors help many people.
If recession has already occurred and exposed metal, you have options. Minor recession might not bother you, and no treatment is needed. Significant recession causing visible metal on front teeth usually requires crown replacement with an all-ceramic crown that has no metal collar, or possibly gum grafting to cover the exposed area again.
What You Should Do Right Now
Schedule a dental examination as soon as possible. Don’t try to diagnose the cause yourself because the consequences of guessing wrong can be serious. If the black spot is decay and you delay, you risk losing the tooth entirely. If it’s cosmetic, you’ll have peace of mind knowing nothing is wrong structurally.
During examination, I check several things: I probe around the crown margin feeling for soft spots indicating decay. I take X-rays to see what’s happening under the crown that isn’t visible clinically. I evaluate gum health around the crown. I assess whether the black spot is surface staining or something deeper.
Based on findings, treatment varies dramatically. Decay requires crown removal, decay treatment, and a new crown. Metal showing through or staining only needs replacement if you want improved appearance. Gum recession might benefit from technique changes to prevent further loss.
If you’re concerned about a black spot on your crown or any other crown issues, I’m available for evaluation at any Picasso Dental Clinic location in Hanoi, Da Nang, Ho Chi Minh City, or Da Lat.
