A dark spot appearing on a tooth can immediately cause worry. Distinguishing between simple discoloration and a developing cavity is often difficult for the untrained observer. While a professional diagnosis from a dentist is ultimately necessary, understanding the basic signs of each provides an important initial assessment. Knowing how stains and cavities differ in appearance, cause, and required treatment helps the reader gauge the seriousness of the situation.
Key Differences in Appearance
At-home observation can offer initial clues about the nature of the dark spot, focusing on texture and location. A surface stain is typically flat and feels smooth to the touch of the tongue or a finger, appearing as if the discoloration is simply painted on the enamel layer. These stains may cover a broad area, follow the lines of the tooth, or present as a general yellowing or browning across multiple teeth.
Cavities often look and feel different because they represent a physical breach in the tooth structure. Decay tends to be localized in pits, fissures (grooves) on the chewing surfaces, or between teeth where plaque is hard to remove. An established cavity may appear as a dark gray or black spot that feels rough, sticky, or may even present as a small, distinct hole or dent. Early decay can also manifest as a chalky white spot, indicating the beginning of mineral loss before the area darkens.
Stains are purely cosmetic and do not cause any discomfort or pain. If a dark spot is associated with sensitivity to hot, cold, or sweet items, or if there is a sharp pain when chewing, this strongly suggests a cavity is present. This pain indicates the decay has reached the dentin layer beneath the enamel.
The Causes of Discoloration and Decay
Discoloration can be classified as extrinsic, meaning it occurs on the outer surface of the tooth’s enamel. This type of stain is caused by chromogens, which are pigment-producing substances found in foods and beverages like coffee, tea, red wine, and berries. Tobacco use is also a significant contributor to extrinsic stains.
Intrinsic stains form within the tooth structure, often in the dentin layer beneath the enamel, and are generally more difficult to remove. These stains may result from trauma, certain medications like tetracycline taken during tooth development, or the natural thinning of enamel with age. This thinning allows the yellowish dentin to show through.
Dental decay, or caries, is a disease process initiated by specific bacteria in the mouth, primarily Streptococcus mutans. This bacterium metabolizes fermentable carbohydrates, such as sugars, producing lactic acid as a waste product. The acid lowers the pH level in the dental plaque biofilm, which begins to dissolve the protective mineral structure of the tooth enamel in a process called demineralization. This cycle of acid production and mineral loss eventually leads to the formation of a cavity, which is a permanent structural defect.
When to See a Dentist and Treatment Options
A dental visit is necessary to accurately determine if a discoloration is a benign stain or active decay. Dentists use several tools beyond visual inspection to confirm a diagnosis, including a dental explorer, which checks for softness or stickiness that indicates compromised tooth structure. The most definitive diagnostic tool is the dental X-ray, which can reveal decay between teeth or under existing restorations that are invisible to the naked eye.
Treatment for a stain depends on its type and depth. Extrinsic stains are often removed during a professional cleaning and polishing procedure. Deeper, intrinsic stains may require chemical treatments, such as professional in-office or take-home whitening systems utilizing hydrogen peroxide gels. For discoloration that resists whitening, cosmetic procedures like dental bonding or porcelain veneers can be used to cover the affected tooth surface.
For a confirmed cavity, treatment involves removing the decayed material. For decay caught early, the dentist cleans the area and restores the tooth using a filling, typically made of composite resin or amalgam. If the decay is extensive, reaching the tooth’s pulp, a more involved procedure like a root canal may be required. This is often followed by placing a crown to restore the tooth’s function and structure.