A black tooth can be a concerning visual change, indicating an underlying process that ranges from a simple, harmless surface stain to a serious, progressive internal condition. This discoloration signals that the tooth’s structure has been affected by external factors or internal damage. Understanding the location and nature of the blackness is the first step in determining the cause and necessary professional intervention.
Progressive Dental Caries
One of the most common causes of a tooth turning black is advanced dental decay. This decay begins when bacteria produce acids that dissolve the mineral structure of the enamel, creating a pathway into the softer, underlying dentin layer. As the decay progresses into the dentin, the damaged tissue absorbs dark pigments from the oral environment, causing the characteristic black or dark brown appearance.
The black color indicates that the decay has been ongoing, breaking down the internal tooth structure. Once the decay reaches the pulp chamber, the nerve tissue can die, leading to internal necrosis that further darkens the tooth from the inside out. This advanced stage often requires restorative procedures, such as a large filling, a crown, or even extraction if the damage is too extensive.
In some cases, the black area may represent “arrested decay,” which is a lesion that has remineralized and is no longer actively progressing. These inactive lesions appear dark because they have incorporated pigments, often ferric sulfide, but they feel hard and glossy to a dental probe. While arrested decay requires monitoring rather than immediate restorative treatment, its presence signals a history of decay activity.
Extrinsic Stains and Surface Factors
Black discoloration can be due to extrinsic factors, meaning the staining is confined to the outer surface of the enamel. This surface staining can result from consuming dark-colored substances like coffee, tea, red wine, or highly pigmented foods. Tobacco use, whether smoking or chewing, is another common source of dark staining, as nicotine and tar compounds adhere strongly to the tooth surface.
Certain mineral supplements, particularly liquid iron tonics, can react chemically in the mouth to produce a black residue. This black coloration is generally harmless to the tooth structure but adheres stubbornly and cannot be removed by simple brushing.
Another specific surface factor is the presence of chromogenic bacteria, such as Actinomyces species, which frequently cause a distinct “black line stain.” These bacteria react with iron in the mouth, resulting in a dark line or a series of dark dots, typically along the gum line. Unlike decay, these surface stains are smooth and do not involve structural damage to the tooth, often indicating a cosmetic issue that requires professional cleaning to resolve.
Intrinsic Causes from Trauma or Materials
A tooth can turn black due to intrinsic causes, which originate from within the tooth structure, often signaling internal injury or the presence of certain materials. A significant blow or trauma to the mouth can rupture the blood vessels inside the pulp chamber, leading to intrapulpal hemorrhage. As the blood breaks down, iron compounds are released that penetrate the dentinal tubules, causing discoloration.
This process often causes the tooth to turn gray, then brown, and eventually black over weeks or months, a condition known as pulp necrosis, or a “dead tooth.” The discoloration signals that the nerve tissue has died, requiring endodontic intervention to prevent infection from spreading.
Discoloration can also be a side effect of past restorative work, specifically older silver amalgam fillings. These fillings contain metallic ions, including silver, which can slowly leach into the surrounding dentin, causing a gray or black shadow. This internal metallic staining is typically visible through the tooth’s enamel. Furthermore, certain dental treatments, such as the application of silver diamine fluoride (SDF) to arrest decay, can cause the treated area to turn dark black upon contact with the carious tissue.
Seeking Professional Evaluation
A dental professional is necessary to accurately diagnose the reason for black discoloration. Self-diagnosis is insufficient because the difference between a harmless surface stain and deep, progressive decay is not always visually apparent. A dentist will perform a thorough visual examination and use a dental probe to assess the texture and hardness of the dark area.
To check for internal issues, the dentist will use dental X-rays to look for signs of decay or infection near the root. Pulp vitality testing may also be performed to determine if the nerve tissue inside the tooth is still alive, especially following a history of trauma. The resulting treatment will vary significantly: professional scaling for extrinsic stains, a filling or crown for active decay, or a root canal for a necrotic tooth.