The enamel layer is whiter and semitransparent, and contributes blue, pink green tints to the tooth color.

[10] The same range of factors are capable of staining the surface of restorations (e.g., composite fillings, porcelain crowns).

[11] Causes of intrinsic discoloration generally fall into those that occur during tooth development and those acquired later in life.

In its mildest form, fluorosis appears as small opaque white flecks on the enamel surface.

[18] Chronological, fine white bands of fluorosis may be seen that correspond to the times of high exposure to fluoride.

This is due to severance of the venous microcirculation to a tooth, while the arteries continue to supply blood to the pulp.

[2] This discoloration typically develops weeks or months after the injury and is caused by incorporation of pigments released during the breakdown of the pulpal tissue and blood into the dentin.

[19] Internal staining is common following root canal treatment; however, the exact causes for this are not completely understood.

[20] Ingestion during the years of tooth development causes a yellow-green discoloration of dentin, which is visible through the enamel and fluorescent under ultraviolet light.

[medical citation needed] Because tetracyclines cross the placenta, a child may have tooth staining if the drugs are administered during the mother's pregnancy.

The enamel is fragile, the teeth appear yellow or brown, and surface stains build up more readily.

[1] Dentinogenesis imperfecta is a defect of dentin formation, and the teeth may be discolored yellow-brown, deep amber or blue-grey with increased translucency.

[1][12] Hyperbilirubinemia during the years of tooth formation may make bilirubin incorporate into the dental hard tissues, causing yellow-green or blue-green discoloration.

[11] 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.

[medical citation needed] Discoloration of the front teeth is one of the most common reasons people seek dental care.

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).

Alternatively the appearance of the tooth can be hidden with dental restorations (e.g., composite fillings, veneers, crowns).