Dental crowns serve as common solutions for restoring teeth affected by decay, damage, or wear. They encase the entire visible portion of a tooth, providing strength, protection, and improved appearance. While durable, a darkening or black discoloration can be concerning. Understanding why a crown might appear dark is important for effective resolution.
Reasons Your Crown May Appear Dark
A common reason for a dark crown, especially at the gumline, is gum recession exposing the metal margin of a porcelain-fused-to-metal (PFM) crown. PFM crowns consist of a metal substructure covered by a tooth-colored porcelain layer. As gums recede due to aging, gum disease, or aggressive brushing, the dark metal edge becomes visible, creating a black line. This is often an aesthetic concern, not necessarily a problem with the crown’s integrity.
External factors can also contribute to a crown’s darkened appearance through staining. Materials like coffee, tea, red wine, and tobacco can deposit pigments onto the crown’s surface over time. This is especially true for older or more porous porcelain materials, which can absorb stains similarly to natural tooth enamel. Regular consumption of highly pigmented foods and drinks can gradually alter the crown’s original shade, making it appear darker.
Decay underneath or around the crown is a more serious cause of darkening. The tooth structure under a crown remains susceptible to cavities, especially at the margins. Progressing decay creates a dark shadow visible through or around the crown, indicating a compromised tooth. This discoloration signals a significant dental problem requiring immediate attention.
Corrosion of metal components in some crowns can cause discoloration. Older full metal crowns or PFM crown substructures (e.g., nickel, chromium, cobalt alloys) can corrode. This process releases metal ions, causing a grayish or blackish tint on or around the crown. Though modern alloys resist corrosion, this can occur with older restorations.
Furthermore, the crown material itself can contribute to a darker appearance if it is old or worn. The porcelain layer on PFM crowns can thin, chip, or wear away over time, gradually exposing the darker metal foundation beneath. This wear can also reduce the crown’s translucency, making it appear duller or darker. Additionally, the natural tooth structure underneath a crown, especially one that has undergone a root canal procedure, can internally darken over time and show through the crown material.
Identifying the Severity of Discoloration
It’s important to distinguish between aesthetic and clinical issues when a crown darkens. A black line at the gumline, common with PFM crowns, is often cosmetic, caused by gum recession exposing metal. This darkening usually poses no immediate health threat, though it affects appearance. However, if the crown changes color entirely or darkening extends beyond the gumline, it may indicate a more serious problem.
There are several accompanying symptoms that serve as red flags, indicating the discoloration may be linked to a more serious underlying dental problem. Experiencing pain, especially when chewing or biting, or persistent sensitivity to hot or cold temperatures, can signal issues like decay or infection beneath the crown. Swelling or redness of the gums around the crowned tooth, a foul taste or odor, or even pus discharge are also strong indicators of infection. A crown that feels loose can further suggest compromised tooth structure underneath.
The discoloration’s location provides clues about its cause. Darkening at the gumline often points to exposed PFM metal or tooth root staining from gum recession. Generalized darkening across the crown’s surface may be external staining. A dark shadow or spot emanating from underneath, rather than on the surface, often indicates underlying tooth decay or intrinsic discoloration from previous treatment.
What to Do About a Dark Crown
If your dental crown darkens, avoid self-removal or repair. Crowns are permanently bonded, requiring specialized tools for safe removal or adjustment. Self-repair could damage the crown, underlying tooth, or oral tissues.
Maintain good oral hygiene to prevent further issues. Brush twice daily and floss around the crowned tooth to remove plaque and food particles that cause staining and decay. Use a soft-bristle toothbrush and non-abrasive toothpaste to protect the crown and gums. Consistent hygiene reduces external stains and preserves appearance.
Schedule a dental appointment for a professional evaluation. Only a dentist can accurately diagnose the darkening’s cause and determine if it’s cosmetic or serious. The dentist will examine the crown, assess gum health, and may take X-rays to check for decay or other underlying issues.
During your dental visit, your dentist will discuss various options for addressing the dark crown, tailored to the specific diagnosis. For surface staining, professional cleaning may be sufficient to restore the crown’s original luster. If gum recession is exposing a metal margin, or if the crown is old and worn, replacement with a modern all-ceramic crown may be recommended for improved aesthetics. In cases of decay underneath the crown, the dentist will need to remove the decay and may either repair the tooth with a filling, perform a root canal, or replace the crown depending on the extent of the damage.