After some time in use, many people notice a dark line at the neck of a porcelain crown, right beside the gum. It is a common issue with crowns that have a metal base.
- A dark line beside the gum on a porcelain crown is usually caused by gum recession exposing the metal edge of a crown with a metal base.
- Gum inflammation around the crown or decay at the margin can also discolour the edge.
- Bleeding, red swelling, pain or bad breath alongside it are signs to be checked early.
- Careful hygiene and regular scaling help keep gums healthy and reduce the dark edge.
Several years after getting porcelain crowns, many people notice a dark or grey line right beside the gum, which makes the tooth look less attractive and raises the worry that the tooth is damaged. This is quite common, especially with crowns that have a metal base inside.
Why does a dark line appear at the neck of a crown?
- Receding gums: the gum pulls back and exposes the metal edge of the crown, which looks like a dark line. See whether gum recession can be treated.
- Gum inflammation around the crown: plaque builds up at the margin, making the gum swollen and dark purple.
- A leaking margin: bacteria seep in and can cause decay underneath, discolouring the edge.
- Crown material: crowns with a metal base show a dark edge more easily than all porcelain ones.
Is the dark line dangerous?
If it is simply an even recession with the metal edge showing, it is mainly a cosmetic matter. But if it comes with red swollen gums, bleeding, pain or bad breath, there may be gum inflammation or decay at the margin of the crown and it should be dealt with early.
What can be done?
- Clean off plaque and tartar around the margin and treat gum inflammation if present.
- Check whether the margin leaks or whether there is decay underneath, with an X-ray if needed.
- If the crown leaks or the tooth underneath is decayed, the dentist may advise making a new crown.
- If it is only an exposed edge from recession and you want a better appearance, the dentist will advise suitable options.
See also whether porcelain crowns harm teeth and what to do when a porcelain crown comes off or breaks.
Prevention
- Brush gently with a soft toothbrush, paying attention to the gum around the crown.
- Clean between the teeth and along the margin with floss or an interdental brush.
- Have tartar removed and regular check ups, see caring for porcelain crowns properly.
When should you visit Ky Hoa Dental Clinic?
Nha Khoa Ky Hoa is at 266A - 268, 3 Thang 2 Street, Hoa Hung Ward, Ho Chi Minh City. You can walk in during opening hours, or call the hotline 028.3868.1097 to ask about quieter times first. The dentist will check the margin of the crown and the gum to find the cause. Please note that cosmetic porcelain crowns are not covered by health insurance.
Frequently asked questions
Why does a porcelain crown have a dark line beside the gum?
Usually because gum recession exposes the metal edge of the crown, or because of gum inflammation or decay at the margin.
Does a dark edge always mean the crown must be redone?
Not always. The dentist will check the margin, the gum and the tooth underneath, then advise a suitable option.
How can a dark edge be prevented?
Brush gently, clean between the teeth and along the margin, and have regular scaling to keep gums healthy and reduce recession.