COLUMN · Treatment

Black Line Around a Crown or a Discolored Crown
Causes and Replacement Options

Medically reviewed by Dr. Sunmin Kim, Board-certified Orthodontist · Last updated 2026-10-22

An old crown that has turned yellow, a dark line at the edge, or gums that look grey around a front tooth. These changes are common, and on front teeth they are easy to see. This article covers why crowns discolor, what you can and cannot do yourself, and the options for replacement.

Why do crowns discolor?

• The material aging: crowns that contain resin (plastic) tend to yellow or dull over time.
• Staining at the edge: stains and plaque collect where the crown meets the tooth, making the line stand out.
• Dark gums: metal posts or metal-based crowns can make the gum edge look dark.
• Old metal: metal inside can show through, or make the surrounding area look darker.

Which cause is the main one depends on the material, when the crown was made and your mouth. It is hard to tell just by looking, so a diagnosis is needed.

What you can and cannot do yourself

What you can do

Surface stains may become less noticeable with careful brushing and professional cleaning. Good plaque control at the edge helps both appearance and gum health.

What you cannot do

Whitening works on natural teeth, but it cannot lighten ceramic or resin. If the crown itself has discolored, whitening will not solve it, and replacing the crown becomes the option.

Replacement options

• Replacing with ceramic: resists discoloration, has translucency and blends with neighbouring teeth.
• Changing to metal-free: a structure without metal may help with dark gums and metal showing through.
• Rebuilding from the core: where an old metal post is the cause, rebuilding including the core may suit.

For front teeth, our clinic uses all-ceramic, zirconia or PFZ crowns; we do not use PFM on front teeth. Which option suits you depends on how much tooth remains, the root and your bite.

Check before replacing

Replacement usually involves removing the crown and preparing the tooth, and it cannot be undone. At the consultation, check:

• the cause of the discoloration (staining, material or metal);
• whether there are problems inside the crown, at the root or in the gums;
• which materials are available and how they differ in appearance and longevity;
• whether your current crown can be kept.

Helping a new crown stay its color

• Keep the edge clean with careful daily care
• Have regular check-ups and cleaning
• Choose a material that resists discoloration with your dentist
• If you smoke or have a lot of staining food and drink, pay extra attention to care

Frequently asked questions

This article is for general information and does not promise any particular result or cost. Suitability, treatment plan, results and how long restorations last differ from person to person. Please have a consultation and examination with a dentist before treatment. Prices are standard list prices as of 2026-10-22 and may change.