Why is there a black line around my PFM dental crown?: 3 Reasons Why!

Patients often ask us, “Doc, what’s this black line around my porcelain-fused-to-metal (PFM) dental crown? Is it dirt?”

The black line isn’t a sign of dirt or age, but it could mean three things: receding gums, the material of the crown or crown fit problems. Let’s explore these causes in greater detail!

1) Receding gums 

The black line is usually a result of the metal part of the crown showing through the porcelain exterior, especially at the gum line. Over time, as gums recede naturally or due to factors like gum disease or aggressive brushing, more of the metal may become visible, creating the appearance of a black line.

Receding gums are a condition where your gums pull back from the tooth surface, exposing the root surface of your tooth and causing your tooth to look long. It is a form of gum disease and is often caused by poor oral hygiene, vigorous tooth brushing, teeth grinding or shifting teeth. If you have receding gums, you may experience sensitivity to hot and cold food and notice some space between your teeth.

If your gums start to recede when you have a dental crown on, that black line may be a part of your natural tooth structure, especially if you’ve had a root canal or traumatic injury before the dental crown procedure. Please note that regardless of material, all dental crowns are susceptible to receding gums, so it’s important to practice good oral hygiene and visit your dentist regularly even with a crown on.

2) Material of the dental crowns 

Before the mainstream use of porcelain crowns, dental crowns were commonly made of porcelain fused with metal. This means the crown is made of a metal base with a porcelain cover. The black line is the junction where the tooth and crown meet — if this margin occurs near the gum line, then a dark line shows. 

In the past, porcelain fused to metal crowns was the standard for crowns due to their strength and natural appearance. Today, all-porcelain and ceramic crowns can provide the same support and aesthetics minus the risk of the black line. At Dental Designs, we use metal-free dental crowns made entirely of modern ceramic materials. This allows us to conserve more tooth volume as well. 

Porcelain crowns are typically more expensive than porcelain fused to metal crowns, but they produce better results and are worth the investment in the long run. 

Find out more about Dental Crowns with Dental Designs today!

3) Dental crown fit problems

You can limit or stop tooth decay and gum recession with good oral hygiene — but if your crown doesn’t fit properly in the first place, all your efforts might go to waste. When a crown is not placed properly, cleaning can be difficult. Over time, this lack of proper cleaning can lead to tooth decay, gum disease, and gum recession. 

Yes, although a crown protects natural tooth structure, decay is still possible without adequate oral hygiene. To prevent a poorly fitted crown, pick a dentist with a good track record with dental implants and restorations and schedule regular dental checkups.

This phenomenon is more common with older crown designs, where the metal framework extends closer to the edge of the crown. While it doesn't necessarily indicate a problem with the crown's function, it can be cosmetically undesirable, particularly for crowns on front teeth.

Related Articles

• How do I check if I have decay around my crown?

• How do I care for my new dental crown?

How do I get rid of the black line around my crown?

The only way to get rid of the black line around your crown is to replace it entirely. The good news is that it is not a difficult process and takes just a few hours of your time. 

Here’s how it’s done: 

• Your dentist will make a slit through your crown and pop the crown off using a special tool. This breaks the bonding seal and removes the crown without damaging your underlying tooth. 
• A new impression of your teeth is taken to create your new crown. With us, this process includes using a 3D CEREC scanner to create a 3D model of your teeth, using the CEREC software to create the shape of your new crown, milling your crown in our in-house lab and finally hand painting it so it looks realistic. Everything is done on the same day. 
• You might experience gum tenderness and soreness after the procedure, but this is normal and should resolve in 2 weeks.
  
  

Many patients find that with their new crown, they look a lot younger and healthier. Your teeth play a huge role in your smile and appearance; if you don’t like the way your crowns look or are looking for a smile makeover, we can help! 

Find out more about Dental Crowns with Dental Designs today!

References 

1. Chowdhuri MA, Xia Z, Yu D. A study on optimal bonding angles of bi-material interfaces in dental crowns with porcelain fused to metal. Proc Inst Mech Eng H. 2011 Jul;225(7):657-68. doi: 10.1177/0954411911401781. PMID: 21870373.
2. Bluma E, Vidzis A, Zigurs G. The influence of fixed prostheses on periodontal health. Stomatologija. 2016;18(4):112-121. PMID: 28980541.