Human oral mucosal epithelium is not uniformly colored and several degrees of chromatic variegation may be observed in physiologic and pathologic conditions. The term “pigmentations of the oral mucosa”may be applied to a wide range of entities caused by the accumulation of one or more pigments and featuring a change in color of the tissues.
Oral pigmentation occurs in all races. There were no significant differences in the oral pigmentation between males and females. The intensity and distribution of racial pigmentation of the oral mucosa is variable, not only between races, but also between different individuals of the same race and within different areas of the mouth.
Pigmentation of the oral mucosa can occur due to a wide variety of lesions and conditions. Oral pigmentation has been associated with a variety of endogenous and exogenous etiologic factors. Most pigmentations are caused by five primary pigments. These include melanin, melanoid, oxyhemoglobin, reduced hemoglobin, and carotene. Others are caused by bilirubin and iron.
Melanin is produced by melanocytes in the basal layer of the epithelium and is transferred to adjacent keratinocytes via membrane-bound organelles called melanosomes. Melanin is also synthesized by nevus cells, which are derived from the neural crest and are found in the skin and mucosa. Pigmented lesions caused by increased melanin deposition may be brown, blue, gray, or black, depending on the amount and location of melanin in the tissues.
Most of the oral pigmentations are physiologic and are probably genetically determined.Dummett suggested that the degree of pigmentation is partially related to mechanical, chemical, and physical stimulation. In darker skinned people, oral pigmentation increases, but there is no difference in the number of melanocytes between fair-skinned and dark-skinned individuals. The variation is related to the differences in the activity of melanocytes.
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