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Tooth discoloration (also termed tooth staining) is abnormal tooth color, hue or translucency. External discoloration is accumulation of stains on the tooth surface. Internal discoloration is due to absorption of pigment particles into tooth structure. Sometimes there are several different co-existent factors responsible for discoloration.
The stained teeth of a regular betel chewer in Burma
Extrinsic discolorations are common and have many different causes. The same range of factors are capable of staining the surface of restorations (e.g., composite fillings, porcelain crowns). Some extrinsic discolorations that are allowed to remain for a long time may become intrinsic.
Dental plaque: Although usually virtually invisible on the tooth surface, plaque may become stained by chromogenic bacteria such as Actinomyces species.
Calculus: Neglected plaque eventually calcifies, and leads to formation of a hard deposit on the teeth, especially around the gumline. The color of calculus varies, and may be grey, yellow, black or brown.
Tobacco: Tar in smoke from tobacco products (and also smokeless tobacco products) tends to form a yellow-brown-black stain around the necks of the teeth above the gumline.
Certain foods and drinks: Foods, such as vegetables, that are rich with carotenoids or xanthonoids can stain teeth. Ingesting colored liquids like sports drinks, cola, coffee, tea and red wine can discolor teeth.
Certain topical medications.
Chlorhexidine (antiseptic mouthwash) binds to tannins, meaning that prolonged use in persons who consume coffee, tea or red wine is associated with extrinsic staining (i.e., removable staining) of teeth.
Cetylpyridinium chloride, which is found in many antimicrobial mouthwashes, can result in staining due to dead bacterial residue.
Metallic compounds. Exposure to such metallic compounds may be in the form of medication or other environmental exposure. Examples include iron (black stain), iodine (black), copper (green), nickel (green) and cadmium (yellow-brown).
Antibiotics. Tetracycline and its derivatives are capable of intrinsic discoloration (discussed below). However other antibiotics may form insoluble complexes with calcium, iron and other elements that cause extrinsic staining.
Causes of intrinsic discoloration generally fall into those that occur during tooth development and those acquired later in life. The known causes of intrinsic staining are listed below, however some causes are unknown:
- Dental caries
- Pulp necrosis
- Internal resorption
- Root canal treatment
- Amalgam fillings
- Tetracycline and tetracycline-derivatives
- Genetic disorders
Intrinsic discoloration tends to accompany aging. Throughout life deposition of secondary dentin occurs along the internal walls of the pulp chamber. Secondary dentin is darker and more opaque than primary dentin. This gives the dentin an overall darker appearance. At the same time, the enamel layer is gradually thinned by tooth wear processes such as attrition and acid erosion, a degree of which is considered normal. Enamel also becomes less porous and phosphate deficient.
Discoloration of the front teeth is one of the most common reasons people seek dental care. However, many people with teeth of normal shade ask for them to be whitened. Management of tooth discoloration depends on the cause. Most discoloration is harmless and may or may not be of cosmetic concern to the individual. In other cases it may indicate underlying pathology such as pulp necrosis or rarely a systemic disorder.
Most extrinsic discoloration is readily removed by cleaning the teeth, whether with “whitening” (i.e., abrasive) toothpaste at home, or as treatment carried out by a professional (e.g., scaling and/or polishing). To prevent future buildup of extrinsic stains, identification of the cause (e.g., smoking) is required.
Intrinsic discoloration generally requires one of the many types of tooth bleaching. Alternatively the appearance of the tooth can be hidden with dental restorations (e.g., composite fillings, veneers, crowns).