Why Is There a Black Line Formed Around the Base of a Dental Crown?
Dental crowns are tooth-shaped caps that are supposed to encase a damaged or structurally compromised tooth. Besides reconstructing the tooth’s appearance, the restorative appliance restores the treated tooth’s strength & functionality. Over years, the crowned tooth does not look the way it used to. A thin black line around the dental crown edges will appear.
It raises various questions like “Is there any damage to the dental crown?”, “Does the crowned tooth start to decay?” or others.
Don’t get tensed, my friend. This problem is commonly seen in dental caps when they are getting older.
A black line around a dental crown is often caused by metal-based PFM crowns, gum recession, cement leakage, or decay near the crown margin. While it is usually a cosmetic issue, a dental examination can determine whether treatment or crown replacement is necessary.
Common Causes of Black Lines Around Dental Crowns
| Cause | Why It Happens | Treatment |
|---|---|---|
| PFM Crown Metal Margin | Metal framework becomes visible | Replace with all-ceramic crown |
| Gum Recession | Gums pull away and expose crown margin | Gum treatment or crown replacement |
| Shadow Effect | Metal blocks light transmission | Replace with metal-free crown |
| Cement Leakage | Crown adhesive deteriorates | Re-cement or replace crown |
| Tooth Decay | Decay develops near crown edge | Remove decay and place new crown |
| Poor Crown Fit | Gap forms between crown and tooth | New properly fitted crown |
What Causes a Black Line Around a Dental Crown?
The possible scenarios responsible for crowns having black lines at the gum line are as follows:
- PFM Crowns – In the past, dental crowns were commonly made of porcelain fused to metal (PFM). The metal base provided strength, while the porcelain layer restored the natural look of the tooth. When first placed, the metal part of the crown was hidden beneath the gumline. However, over time, as the crown loosened or gums receded, the metal framework could become visible, creating a dark line near the gum. This dark line is primarily due to the metallic structure of PFM crowns.
- Shadow of the crown – Our teeth are translucent in nature. When a beam of light hits a tooth, it can travel around the tooth, including the roots. When a tooth is covered with a PFM crown, the metal layer blocks light from passing through the entire tooth structure. This creates an optical shadow where the crown edge meets the gumline, resulting in a visible dark line above the crown.
- Leakage of cementing agents – Excessive force on a crowned tooth often from habits like teeth grinding or clenching can cause the adhesive holding the crown to weaken or leak. This leakage can lead to noticeable discoloration near the gumline.
Are the black lines around dental crown a sign of tooth decay?
In rare cases, the black line can happen due to cavities.
Decay in the crowned tooth’s natural portion especially the margins is possible. If it occurs, the margin will turn dark.
On the other hand, ill-fitting crowns would have an allergic reaction in the surrounding gums. It causes the gums to recede, revealing the tooth’s underlying regions that are normally concealed. Since the exposed areas are dark-colored, they appear as a dark line.
How to get rid of the black line above teeth?
Whether the dark spots occur due to the metal framework or bacteria invasion, your dentist would remove the existing crown.
Nowadays, dental crowns made up of porcelain are highly recommended. They do not contain any metal counterparts whilst the porcelain crowns are also sturdy and provide cosmetic benefits.
So you don’t have to worry about getting black lines when the porcelain crowns become old.
Meanwhile, porcelain crowns ensure the teeth’ translucent appearance. It means the dark shadow created through optical illusion is also eliminated.
If cavities or gum infections are the cause of unattractive dark lines around teeth crowns, the victim should undergo appropriate treatments. Then a new dental cap is placed over the tooth once the infected regions are healed.
Bottom Line
The visibility of metal counterparts in a dental crown produces a black or brown on a tooth around the crown margins. Infections in the crowned tooth and surrounding gums also contribute to this cosmetic concern. Make sure the crowned teeth are clean as well as the natural teeth.
Eliminating those black lines around dental crowns is not a big deal. You can get numerous treatment options to fix this issue in a dental clinic.
