When a dark spot appears on a tooth, the immediate concern is the possibility of a cavity (dental caries). While cavities are a common dental problem requiring intervention, a black or dark spot on a tooth surface does not automatically confirm active decay. Many different factors can lead to enamel discoloration, and understanding these alternatives can help reduce worry until a professional assessment is made.
When Black Spots Indicate Active Decay
Active decay results from a progressive process where acid produced by oral bacteria erodes the tooth structure. This process, called demineralization, begins with the loss of minerals from the hard outer layer of the tooth (enamel). If decay progresses past the initial stage, it penetrates deeper, causing discoloration that appears brown or black as it nears or enters the underlying dentin.
In its active, late-stage form, decay typically presents as a visible hole or pit on the tooth surface. The texture is a significant indicator, as active lesions feel soft, rough, or sticky when a dentist probes them. This softness confirms the lesion is progressing and requires immediate treatment. Advancing decay can also cause symptoms like pain, sensitivity to temperature changes, or discomfort when chewing.
Common Non-Caries Causes of Dark Spots
Many dark spots are stains or surface anomalies that do not threaten the tooth’s structural integrity. Extrinsic staining is a common cause, resulting from pigment particles accumulating on the outer enamel surface. Frequent consumption of dark beverages (coffee, tea, red wine) and tobacco use leave behind dark residues. These stains are typically smooth and can often be removed during a professional dental cleaning.
Another frequent cause is the buildup of tartar (dental calculus), which is hardened plaque. Tartar absorbs pigments from food and drink, causing it to appear dark brown or black, especially along the gum line. This hardened material cannot be removed by simple brushing and requires specialized tools used by a dental hygienist.
A spot may also be a sign of arrested decay—a lesion that demineralized but has since stopped progressing. These spots are often dark brown or black because they have incorporated pigments into the remineralized, hardened surface. The key difference is texture: arrested decay is hard and shiny, unlike active decay, and generally does not require restorative treatment.
Old dental work can create the appearance of a dark spot or shadow on a tooth. Amalgam fillings, made of a silver-colored metal alloy, can cause the surrounding tooth structure to take on a grayish or dark tint. This discoloration is a benign effect of the metal and does not indicate a new cavity or a problem with the filling.
Professional Assessment and Diagnosis
Since it is impossible to distinguish between a harmless stain and active decay by looking in a mirror, a professional assessment is necessary. The diagnostic process begins with a thorough visual inspection of the dark spot’s location, size, and color. Location is often revealing, as decay commonly occurs in the deep grooves on chewing surfaces or between teeth.
The next step involves a tactile examination using a specialized instrument called a dental explorer. The dentist probes the dark area to check for texture changes, specifically looking for the softness or stickiness that indicates progressive loss of tooth material. A hard, smooth surface suggests a stain or arrested decay, while a soft or rough surface points toward an active lesion.
Radiographs (X-rays) are a tool for confirming the diagnosis, as they allow the dentist to see beneath the enamel surface. These images reveal if decay has penetrated the enamel into the dentin, especially in areas between teeth where visual inspection is not possible. If a dark spot is accompanied by symptoms like sensitivity or pain, or if the spot is visually growing, it warrants immediate professional attention.