A black or dark-colored tooth is a major symptom of pulpal necrosis—the medical term for a dead tooth. However, this discoloration is not a certainty of death, as the same black or gray appearance can also be caused by several other, less severe issues. Determining the precise cause is essential because a truly dead tooth requires immediate attention to prevent the spread of infection. Other types of discoloration may only require cosmetic or restorative treatment.
Why Teeth Turn Dark
A tooth can turn dark due to changes occurring either on the surface (extrinsic) or deep within its structure (intrinsic). The most concerning intrinsic discoloration occurs when the pulp tissue inside the tooth dies following trauma or untreated decay. This process involves the breakdown of blood cells, which release hemoglobin into the surrounding dentin, the porous layer beneath the enamel.
The iron within the hemoglobin then combines with hydrogen sulfide, a byproduct of tissue decomposition, to form black iron sulfides. These compounds penetrate the tiny tubules within the dentin, causing the tooth to appear dark gray, brown, or black from the inside out. The longer this necrotic tissue remains inside the tooth chamber, the more intense the resulting discoloration becomes.
However, not all dark color is a sign of internal death. The physical presence of extensive tooth decay can also appear black or dark brown. This discoloration is caused by the actual waste products and pigments created by bacteria breaking down the tooth structure. If the decay is widespread, it can make the entire tooth look dark, even if the internal nerve tissue is still alive.
External factors also frequently cause dark spots or overall darkening. Certain foods, dark beverages like coffee and red wine, and tobacco products contain pigments that adhere directly to the enamel surface, leading to extrinsic staining. Additionally, old silver amalgam fillings can cast a dark shadow through the tooth structure or visibly stain the surrounding area.
The Biological Reality of a Dead Tooth
When a tooth is described as “dead,” the condition is clinically known as pulp necrosis. The dental pulp is the soft tissue core of the tooth, containing nerves, connective tissue, and the blood vessels that supply the tooth with oxygen and nutrients. Necrosis occurs when this blood supply is cut off, typically due to profound decay, a severe crack, or physical trauma.
Once the pulp tissue is deprived of its blood supply, it begins to die, and the nerves cease to function. In the early stages of pulp issues, a tooth may exhibit extreme, lingering sensitivity to hot or cold temperatures. Once full necrosis occurs, the nerve is no longer able to transmit pain signals, so the tooth may suddenly become completely asymptomatic, or “painless,” which can be misleading.
The danger of pulp necrosis is not the discoloration itself, but the fact that the dead tissue acts as a breeding ground for bacteria. These bacteria multiply and can exit the tip of the tooth root, spreading infection into the surrounding jawbone. This process leads to the formation of a periapical abscess that causes bone loss and can result in significant swelling of the gums or face.
If a necrotic tooth is left untreated, the infection can potentially spread beyond the jawbone to other areas of the body, creating serious systemic health risks.
Diagnosis and Necessary Treatment
Determining whether a dark tooth is truly necrotic requires a combination of clinical tests and diagnostic imaging performed by a dentist. The most common diagnostic tools are pulp vitality tests, which assess the health of the internal nerve and blood supply. Thermal tests involve applying a cold stimulus, often a specialized spray, to the tooth to see if a healthy, sharp sensation is felt, which would indicate a vital pulp.
Electric pulp testing uses a small electrical current to stimulate the nerve fibers within the pulp; a response suggests the nerve is still alive, while a lack of response points toward necrosis. Since these methods only test the sensory response, dentists also rely on X-rays, or radiographs, to look for signs of chronic infection. A dark area visible at the tip of the root on an X-ray, known as a periapical radiolucency, confirms the presence of a necrotic pulp by showing bone destruction caused by bacteria.
If the dentist confirms pulp necrosis, the primary treatment is Root Canal Therapy (RCT). This procedure involves cleaning out all the infected and necrotic tissue from the pulp chamber and root canals, disinfecting the space, and then sealing it to prevent reinfection. RCT saves the natural tooth structure and prevents the need for extraction.
For teeth that are too compromised to be saved, extraction is the final option. Once the underlying biological problem is resolved, the remaining discoloration can be treated; the most conservative option for a dark tooth that has had a root canal is internal bleaching. This involves placing a whitening agent directly inside the tooth to lighten the stained dentin from within. For teeth that are structurally weak or severely discolored, a crown or veneer may be placed over the tooth to restore its appearance and provide necessary reinforcement.