Light and electron microscopic studies of retzius lines in human cervical enamel

Unaltered mature enamel and partially demineralized mature enamel from the cervical third of human permanent teeth were examined by means of transmission electron microscopy, microradiography, phase contrast and Nomarski differential interference microscopy. The Retzius lines in the outer third of the cervical enamel had a staircase configuration. The steps in the stair‐case pattern formed the bases of triangular regions which were radiolucent and ultrastructurally contained fewer crystallites than the adjacent enamel. In the outer prismless layer, the Retzius lines had a curvilinear configuration and were also crystallite deficient. The structure of the Retzius lines in the inner portion of the cervical enamel was not nearly as well defined.