Light microscopic observations on the formation of the layer of Hopewell-Smith in human teeth

Abstract

Light microscopic examination of longitudinal ground sections of incompletely formed teeth revealed a layer on the external root surface of dentine which was continuous at the forming apex with the predentine. Dentinal tubules were observed transversing this layer, particularly in the cervical region. In more completely formed teeth, the layer was not clearly defined, though tubules were still present which reached the root surface. Examination of tetracycline-labelled sections by light and fluorescent microscopy showed a band pattern which, taken with the previous evidence, led to the conclusion that an additional delayed calcification at the dentine root surface occurs after some calcified dentine has been laid down, but before any cement deposition. The situation of this calcification zone, external to the granular layer of Tomes, corresponded with the layer of Hopewell-Smith, and the evidence suggested that terminal portions of odontolast processes might be involved in its formation.