The appearance of a tooth turning black signals a significant change in the tooth’s structure, whether on the surface or deep within the internal layers. This discoloration is a visible manifestation of an underlying issue, ranging from a relatively harmless surface stain to advanced structural damage. Understanding this change requires differentiating between discoloration adhering to the outer enamel and changes originating from within the tooth’s core to determine the necessary professional intervention.
External Sources of Dark Staining
Darkening that affects the exterior of the tooth is known as extrinsic staining, where pigment adheres directly to the enamel or the pellicle. One common cause is the presence of chromogenic bacteria, such as Actinomyces species, which produce color. These microbes interact with iron in saliva or gingival fluid to form an insoluble ferric sulfide compound, appearing as a distinct black line or series of dots near the gumline. This surface stain is aesthetic and does not indicate decay, but it resists normal brushing and requires professional attention.
Other major contributors to extrinsic black staining are specific dietary habits and substances containing intense pigments (chromogens). Frequent consumption of items like coffee, tea, and red wine introduces tannins and pigments that lodge in the microscopic irregularities of the enamel.
Tobacco use, both smoking and chewing, deposits tar and nicotine compounds that create tenacious, dark brown to black stains. Metallic compounds from certain mouth rinses or medications, such as liquid iron supplements, are also relevant. These metallic ions react with sulfur compounds in the mouth to create dark precipitates on the enamel surface.
Internal Changes That Cause Teeth to Darken
When discoloration originates from within the tooth structure, it is termed intrinsic staining, indicating a change to the dentin, the layer beneath the enamel, or the pulp chamber. A common intrinsic cause is physical trauma to the tooth, which damages the blood vessels and nerves inside the pulp.
This injury results in internal bleeding, causing blood breakdown products like hemoglobin to seep into the dentinal tubules. As these components degrade, iron is released, combining with hydrogen sulfide to form a dark compound, permanently staining the dentin. If trauma cuts off the blood supply, the pulp tissue dies, a process called pulp necrosis. The decomposition of this dead tissue causes the tooth to gradually shift to a dark gray, brown, or black hue over a period of weeks or months.
Systemic factors and medications also contribute to intrinsic discoloration, especially during tooth development. A notable example is the ingestion of tetracycline antibiotics by a child or pregnant person, which causes the drug to bind to calcium in the developing dentin and enamel. The resulting stain is permanent, often appearing as a dark gray, blue-gray, or brown discoloration that is evenly distributed across the affected teeth.
Understanding Advanced Dental Decay
The most concerning cause of a tooth turning black is advanced dental decay, also known as severe dental caries. This blackening signals that the destructive process, initiated by acid-producing bacteria, has progressed deep into the tooth structure.
The bacteria metabolize dietary sugars and starches to release acid, which begins the process of demineralization, dissolving the mineral content of the enamel and dentin. The discoloration progresses from an initial white spot lesion to brown and eventually black cavitation as the decay advances. This dark color is a consequence of structural collapse in the dentin, where the organic matrix is compromised and traps pigments.
When the decay reaches the dentin, the softer tissue allows the process to accelerate, leading to the formation of a large, dark cavity. The black appearance is a strong indicator of a deep infection that requires restorative treatment to prevent its spread into the pulp. If the decay reaches the pulp chamber, the tissue will become infected and necrotic, leading to the internal darkening characteristic of a “dead” tooth. This structural damage is irreversible and cannot be removed by simple cleaning.
Next Steps for Diagnosis and Resolution
A tooth that has turned black requires professional evaluation to accurately determine the underlying cause and the extent of the damage. The diagnostic process typically begins with a thorough visual inspection to differentiate between external stains and structural changes. The dentist will also use dental X-rays, which are essential for revealing issues that are not visible on the surface, such as the depth of decay, the presence of an infection at the root tip, or internal changes following trauma. Treatment is directly guided by the diagnosis, with solutions tailored to the specific source of the discoloration.
Treatment for Extrinsic Stains
For extrinsic stains caused by diet or chromogenic bacteria, the discoloration can typically be resolved with a professional dental cleaning and polishing. This procedure uses specialized instruments to safely remove the tenacious deposits from the enamel surface.
Treatment for Intrinsic Staining
If the blackness is due to intrinsic staining from trauma or pulp necrosis, the tooth is often treated with root canal therapy to remove the dead or damaged pulp tissue. Following this procedure, internal bleaching, where a whitening agent is placed inside the tooth, may be performed to lighten the dentin. Alternatively, cosmetic coverage with a veneer or crown can be used to mask the permanent discoloration.
Treatment for Advanced Decay
When advanced decay is the cause, the treatment is restorative, focusing on removing all diseased tooth structure. Smaller areas of decay may be managed with a filling, while more extensive damage may necessitate a crown to protect the remaining tooth. In cases where the tooth is too severely compromised to be saved, extraction may be the only option.