incremental lines

incremental lines n pl lines seen in a tooth in section showing the periodic depositions of dentin, enamel, and cementum occurring during the tooth's growth

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lines showing the successive layers deposited in a tissue. In the enamel, they are brown striations visible under transmitted light and colorless in reflected light. They may be observed under the microscope in longitudinal sections as oblique lines running inward from the surface and toward the root and in cross sections as rings similar to those in a tree trunk. Dry dentin often shows a series of somewhat parallel lines caused by imperfectly calcified dentin arranged in layers. Called also accretion, calcification, or Retzius l's and Retzius parallel striae. See also l's of Ebner, imbrication l's of Pickerill, and neonatal l.