Black pigmentation in primary dentition: Case report and literature review

Black tooth staining is an extrinsic discoloration found in both primary and permanent dentition, and seen as dark pigmented lines extending to the gingival margin or an incomplete coalescence of dark dots that rarely extend beyond the cervical third of the crown. An association between black tooth staining and Actinomyces bacterial strains has been reported, while black-pigmented bacteria associated with such staining are known to be harbored in the oral cavity. Prevotella intermedia and Prevotella nigrescens are black-pigmented bacteria known to be dependent on the heme portion of hemoglobin as an iron source required for their growth. Recently, developments in molecular biological techniques have enabled rapid and easy detection of periodontopathic bacterial species using bacterial DNA extracted from oral specimens, such as plaque and saliva. Here, we report a case of black pigmentary deposition identified on all teeth of a 2-year-old girl, as well as the results of analysis of the distribution of oral bacteria in saliva and plaque specimens obtained from the patient using a molecular biological technique. In addition, a literature search found a case of disease related to the oral bacteria detected in our patient. We concluded that the bacteria detected in this case may have a strong relationship with black pigmentation, although the route of bacterial infection and cause of staining remain to be elucidated.