Tooth discoloration

Tooth discoloration 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. Tooth discoloration 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 appearance and perception of a tooth is the result of a complex interaction of factors such as lighting conditions, translucency, opacity, light scattering, gloss and the human eye and brain. Of these, the intrinsic pigmentation of a tooth is the most influential, which in turn is determined by genetic and natural factors. Light hitting a tooth undergoes reflection, absorption and transmission by varying degrees in each tissue layer of the tooth substance. Reflected light detected by the human eye determines the perceived appearance of a tooth. Teeth have a thin enamel layer on the outer surface. The enamel layer is whiter and semitransparent, and contributes blue, pink green tints to the tooth color. The underlying dentin layer is darker than enamel, yellow-brown in color, and less transparent. Dentin forms the bulk of the tooth substance, and contributes most to the overall tooth color. At the core of the tooth is soft connective tissue termed the dental pulp. The pulp is pink/red due to its vascularity, but is rarely visible through the overlying enamel and dentin unless the thickness of these layers is reduced by tooth wear (or rarely internal resorption). Public opinion of what is normal tooth shade tends to be distorted. Portrayals of cosmetically enhanced teeth are common in the media. In one report, the most common tooth shade in the general population ranged from A1 to A3 on the VITA classical A1-D4 shade guide. Tooth color varies according to race, gender and geographic region. Females generally have slightly whiter teeth than males, partly because females' teeth are smaller, and therefore there is less bulk of dentin, partially visible through the enamel layer. For the same reason, larger teeth such as the molars and the canine (cuspid) teeth tend to be darker. Baby teeth (deciduous teeth) are generally whiter than the adult teeth that follow, again due to differences in the ratio of enamel to dentin. 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. 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 (tooth decay) begins as an opaque white spot on the surface of the enamel. As demineralization progresses, the various lesion eventually cavitates and the underlying brown color becomes visible. Fluorosis may occur when there is chronic and excessive exposure to fluoride during the years of tooth development. Fluoride is a naturally occurring mineral in water, although some regions have higher levels than others, and in some areas fluoride is added to water supplies in low levels to help prevent tooth decay. Exposure can also occur via bottled water and fluoride toothpaste. In its mildest form, fluorosis appears as small opaque white flecks on the enamel surface. More severe cases show severely hypoplastic patches of enamel, which are also prone to accumulation of surface stains. Chronological, fine white bands of fluorosis may be seen that correspond to the times of high exposure to fluoride.