the Black Line at the Gum Edge of Your Dental Crown

Q: the Black Line at the Gum Edge of Your Dental Crown

Hello： Based on what you mentioned, the physician's statements and actions are both reasonable and normal. <br>Additionally, there are currently no other reasons (such as swelling or discomfort) that would necessitate the removal and remaking of the dentures. <br>It is recommende

There is a black line along the gum margin on the inner side of the front tooth braces?

I have four front teeth, two on the upper left and two on the upper right, that underwent root canal treatment for the first time 20 years ago.
This year, they received a second root canal treatment, and all four teeth were fitted with posts because I did not have crowns placed previously.
Over time, they have noticeably discolored and developed pitting.
An X-ray examination showed that the root canals were not perfectly done.
Today, I had the crowns temporarily cemented in place.
I asked my dentist whether the crowns should be inserted into the gums or aligned with the gum line.
I noticed a very slight gap at the inner gum edge when wearing the temporary crown.
The dentist explained that the outer side of the front teeth crowns is inserted into the gums for aesthetic reasons, while the inner side is aligned with the gum edge for easier cleaning and does not penetrate the gums.
Additionally, because I had a root canal a long time ago, the discoloration of my teeth is quite noticeable, which creates the appearance of a thin black line between the crown and the gum.
Is this normal? When I look in the mirror, I see a faint black line at the junction of the inner side of the crown and the gum, but there is no such line on the outer side.
It feels like the outer gum is covering the crown, while there is a thin black line between the inner gum edge and the crown.
I am unsure if this is due to the inner crown being slightly shorter and not aligning with the gum or if it is simply that the crown is not inserted into the gum but rather aligned with the gum edge.
Given my significant discoloration, I wonder if this thin black line is a normal occurrence.
Before I had the crowns, my teeth were indeed noticeably dark, with shades of brown and black.

I would like to know if this thin black line on the inner side of my front teeth is normal or if it indicates that the crown was not properly fitted or is too short.
Should the gums completely cover the crown? Since there is no black line on the outer side, why is there one on the inner side? My dentist mentioned that the outer side of the front teeth is covered by the gums, while the inner side is aligned with the edge of the gums for easier cleaning.
Is this approach correct, or should I be concerned? As long as I maintain proper hygiene, is this acceptable? I opted for a full porcelain crown, choosing a material that is less translucent and harder.
I did not experience this issue with the crown placed on my lower right molar four years ago at a different clinic.
Thank you.

Li Qiuqiu, 30~39 year old female. Ask Date: 2021/09/11

Dr. Lin Jiayong reply Dentistry

Hello: Based on what you mentioned, the physician's statements and actions are both reasonable and normal.
Additionally, there are currently no other reasons (such as swelling or discomfort) that would necessitate the removal and remaking of the dentures.
It is recommended to maintain proper cleaning.
Sincerely, Lin Chia-Yung, Department of Dentistry, Taichung Hospital, Ministry of Health and Welfare.

Reply Date: 2021/09/11

More Info

Understanding the presence of a black line at the gum edge of your dental crown can be concerning, especially after undergoing significant dental procedures like root canals and crowns. The black line you are observing is often a result of several factors related to the materials used in dental restorations and the way they interact with your natural teeth and gums.

Firstly, it’s essential to understand that dental crowns, especially those made from materials like porcelain fused to metal (PFM), can sometimes show a dark line at the gum line. This line is typically due to the metal substructure of the crown becoming visible as the gum tissue recedes over time. Gum recession can occur for various reasons, including periodontal disease, aggressive brushing, or simply the aging process. If your crown has a metal base, this could explain the black line you see.

In your case, since you mentioned that you have had root canals and that your teeth have undergone significant changes in color, it is possible that the black line is also a result of the discoloration of the underlying tooth structure. When teeth undergo root canal treatment, they can sometimes become darker due to the breakdown of the pulp tissue and the subsequent staining of the tooth structure. If your crown is not fully covering the discolored area of the tooth, this could also contribute to the appearance of a black line.

Your dentist’s explanation that the outer side of the crown is designed for aesthetics while the inner side is placed flush with the gum line for easier cleaning is a common practice in dentistry. This design helps maintain a natural appearance while allowing for effective oral hygiene. The fact that you do not see a black line on the outer side of the crown suggests that the crown is well-contoured and that the gum tissue is healthy in that area.

Regarding your concern about whether the crown is too short or improperly fitted, it is essential to trust your dentist's assessment. If the crown is designed to sit flush with the gum line on the inner side, it should not pose any issues as long as you maintain good oral hygiene. However, if you are experiencing discomfort or if the black line is accompanied by other symptoms such as swelling or pain, it would be prudent to follow up with your dentist for a thorough examination.

In terms of the materials used, you mentioned that you opted for a less translucent and harder type of porcelain crown. This choice can affect the aesthetic outcome, especially if the underlying tooth structure is discolored. While these crowns are durable and can provide excellent function, they may not mask underlying discoloration as effectively as more translucent materials. If the appearance of the black line is a significant concern for you, discussing alternative materials or options with your dentist could be beneficial.

Lastly, it’s crucial to maintain regular dental check-ups and cleanings to monitor the health of your gums and the integrity of your crowns. If you notice any changes in the appearance of the black line or if you experience any discomfort, do not hesitate to reach out to your dentist. They can provide you with tailored advice and treatment options based on your specific situation.

In summary, the black line at the gum edge of your dental crown can be attributed to several factors, including the materials used, gum recession, and the underlying tooth's discoloration. Your dentist's approach to crown placement seems reasonable, and as long as you maintain good oral hygiene and monitor any changes, you should be in good shape. If concerns persist, a follow-up consultation with your dentist is always a good idea.

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