The biology of cementum increments (with an archaeological application)

Abstract Cementum, a bone‐like tissue that surrounds the roots of teeth, anchoring them to the periodontal ligament, is useful for determining the age at and season of death of mammals, an issue of concern for both archaeologists and biologists. When a tooth is sectioned and examined microscopically, cementum appears in bands that differ in their optical properties and are well correlated with seasonal growth. Because it is a continually deposited tissue that is rarely modified or resorbed, cementum records the history of a variety of seasonal factors that affect its growth. An understanding of the biological nature of cementum is crucial to the identification of these factors and interpretation of the resulting incremental structure. This paper outlines current knowledge of the development, histology and function of cementum in the context of the mammalian masticatory apparatus. Of the various types of cementum, acellular cementum is often more appropriate for seasonal correlations. Differences between acellular cementum increments are probably related to specific dietary factors that often vary between seasons. Cellular cementum increments probably result from phasic cementogenesis triggered by tooth eruption. This paper outlines a study of cementum bands in Gazella gazella for which there is an excellent correlation between the season of death and incremental structures in their cementum. This correlation can be used to estimate the season of death of gazelles from archaeological sites in the Levant. Problems for future research are outlined.